WorldWideScience

Sample records for underwater sound absorbing

  1. Sound Absorbers

    Science.gov (United States)

    Fuchs, H. V.; Möser, M.

    Sound absorption indicates the transformation of sound energy into heat. It is, for instance, employed to design the acoustics in rooms. The noise emitted by machinery and plants shall be reduced before arriving at a workplace; auditoria such as lecture rooms or concert halls require a certain reverberation time. Such design goals are realised by installing absorbing components at the walls with well-defined absorption characteristics, which are adjusted for corresponding demands. Sound absorbers also play an important role in acoustic capsules, ducts and screens to avoid sound immission from noise intensive environments into the neighbourhood.

  2. Underwater Sound Reference Division

    Data.gov (United States)

    Federal Laboratory Consortium — The Underwater Sound Reference Division (USRD) serves as the U.S. standardizing activity in the area of underwater acoustic measurements, as the National Institute...

  3. Calibration of Underwater Sound Transducers

    OpenAIRE

    H.R.S. Sastry

    1983-01-01

    The techniques of calibration of underwater sound transducers for farfield, near-field and closed environment conditions are reviewed in this paper .The design of acoustic calibration tank is mentioned. The facilities available at Naval Physical & Oceanographic Laboratory, Cochin for calibration of transducers are also listed.

  4. Underwater Sound Propagation from Marine Pile Driving.

    Science.gov (United States)

    Reyff, James A

    2016-01-01

    Pile driving occurs in a variety of nearshore environments that typically have very shallow-water depths. The propagation of pile-driving sound in water is complex, where sound is directly radiated from the pile as well as through the ground substrate. Piles driven in the ground near water bodies can produce considerable underwater sound energy. This paper presents examples of sound propagation through shallow-water environments. Some of these examples illustrate the substantial variation in sound amplitude over time that can be critical to understand when computing an acoustic-based safety zone for aquatic species.

  5. WODA technical guidance on underwater sound from dredging

    NARCIS (Netherlands)

    Thomsen, F.; Borsani, F.; Clarke, D.; Jong, C. de; Wit, P. de; Goethals, F.; Holtkamp, M.; Martin, E.S.; Spadaro, P.; Raalte, G. van; Victor, G.Y.V.; Jensen, A.

    2016-01-01

    The World Organization of Dredging Associations (WODA) has identified underwater sound as an environmental issue that needs further consideration. A WODA Expert Group on Underwater Sound (WEGUS) prepared a guidance paper in 2013 on dredging sound, including a summary of potential impacts on aquatic

  6. The WODA guidance paper on underwater sound from dredging (abstract)

    NARCIS (Netherlands)

    Thomsen, F.; Borsani, F.; Clarke, D.; Jong, C.A.F. de; Witt, P. de; Holtkamp, M.; Goethals, F.; San Martin, E.; Spadaro, P.; Raalte, G. van; Jensen, A.

    2013-01-01

    The World Organisation of Dredging Associations (WODA) has identified underwater sound as an environmental issue that needs further consideration. A WODA Expert Group on Underwater Sound (WEGUS) was established to provide a guidance paper on dredging sound, impact on aquatic biota and advice on

  7. Design and implementation of an underwater sound recording device

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Jayson J.; Myers, Joshua R.; Carlson, Thomas J.; Deng, Zhiqun; Rohrer, John S.; Caviggia, Kurt A.

    2011-09-19

    The purpose of this study was to design and build two versions of an underwater sound recording device. The device designed is referred to as the Underwater Sound Recorder (USR), which can be connected to one or two hydrophones or other underwater sound sensors. The URS contains a 26 dB preamplifier and a user selectable gain that permits additional amplification of input to the system from 26 dB to 46 dB. Signals within the frequency range up to 15 kHz may be recorded using the USR. Examples of USR applications are monitoring underwater processes that have the potential to create large pressure waves that could potentially harm fish or other aquatic life, such as underwater explosions or pile driving. Additional applications are recording sound generated by vessels or the vocalizations of some marine mammals, such as the calls from many species of whales.

  8. An electromechanical low frequency panel sound absorber.

    Science.gov (United States)

    Chang, Daoqing; Liu, Bilong; Li, Xiaodong

    2010-08-01

    The sound absorbing properties of a thin micro-perforated plate (MPP) coated with piezoelectric material with shunt damping technology is investigated. First a theoretical model is presented to predict the sound absorption coefficients of a thin plate attached with a piezoelectric patch and electrical circuits. Then the model is extended to analyze the sound absorption for a thin plate with micro perforations and piezoelectric material. Measurements are also carried out in an impedance tube and found to be in good agreements with the theoretical model. The sound absorption of the constructions can be much improved by tuning the electrical circuits.

  9. Underwater and in-air sounds from a small hovercraft

    Science.gov (United States)

    Blackwell, Susanna B.; Greene, Charles R.

    2005-12-01

    Underwater and in-air recordings were made from a boat anchored near Prudhoe Bay, Alaska, while a Griffon 2000TD hovercraft drove by at or near full power on four passes. At the closest point of approach (CPA, 6.5 m), underwater broadband (10-10 000 Hz) levels reached 133 and 131 dB re: 1 μPa at depths of 1 and 7 m, respectively. In-air unweighted and A-weighted broadband (10-10 000 Hz) levels reached 104 and 97 dB re: 20 μPa, respectively. The hovercraft produced sound at a wide range of frequencies. Both underwater and in air, the largest spectral peak was near 87 Hz, which corresponded to the blade rate of the thrust propeller. In addition, the spectral composition included several harmonics of this frequency. The shaft or blade rate of the lift fan was barely detectable underwater despite its proximity to the water. The hovercraft was considerably quieter underwater than similar-sized conventional vessels and may be an attractive alternative when there is concern over underwater sounds.

  10. Underwater sound produced by individual drop impacts and rainfall

    DEFF Research Database (Denmark)

    Pumphrey, Hugh C.; Crum, L. A.; Jensen, Leif Bjørnø

    1989-01-01

    ; the second occurs for some impacts but not others. A range of conditions is described in which a bubble is produced for every drop impact, and it is shown that these conditions are likely to be met by a significant fraction of the raindrops in a typical shower. Underwater sound produced by artificial as well...

  11. Sources of underwater sound and their characterisation (abstract)

    NARCIS (Netherlands)

    Ainslie, M.A.; Jong, C.A.F. de

    2013-01-01

    After centuries of speculation, punctuated by occasional theoretical or experimental advances, the first intensive research into underwater sound took place 100 years ago, applied initially to provide advance warning of icebergs after the loss of RMS Titanic in 1912, and later to counter the U-boat

  12. Design and implementation of an underwater sound recording device.

    Science.gov (United States)

    Martinez, Jayson J; Myers, Josh R; Carlson, Thomas J; Deng, Z Daniel; Rohrer, John S; Caviggia, Kurt A; Woodley, Christa M; Weiland, Mark A

    2011-01-01

    To monitor the underwater sound and pressure waves generated by anthropogenic activities such as underwater blasting and pile driving, an autonomous system was designed to record underwater acoustic signals. The underwater sound recording device (USR) allows for connections of two hydrophones or other dynamic pressure sensors, filters high frequency noise out of the collected signals, has a gain that can be independently set for each sensor, and allows for 2 h of data collection. Two versions of the USR were created: a submersible model deployable to a maximum depth of 300 m, and a watertight but not fully submersible model. Tests were performed on the USR in the laboratory using a data acquisition system to send single-frequency sinusoidal voltages directly to each component. These tests verified that the device operates as designed and performs as well as larger commercially available data acquisition systems, which are not suited for field use. On average, the designed gain values differed from the actual measured gain values by about 0.35 dB. A prototype of the device was used in a case study to measure blast pressures while investigating the effect of underwater rock blasting on juvenile Chinook salmon and rainbow trout. In the case study, maximum positive pressure from the blast was found to be significantly correlated with frequency of injury for individual fish. The case study also demonstrated that the device withstood operation in harsh environments, making it a valuable tool for collecting field measurements.

  13. Design and Implementation of an Underwater Sound Recording Device

    Directory of Open Access Journals (Sweden)

    Christa M. Woodley

    2011-09-01

    Full Text Available To monitor the underwater sound and pressure waves generated by anthropogenic activities such as underwater blasting and pile driving, an autonomous system was designed to record underwater acoustic signals. The underwater sound recording device (USR allows for connections of two hydrophones or other dynamic pressure sensors, filters high frequency noise out of the collected signals, has a gain that can be independently set for each sensor, and allows for 2 h of data collection. Two versions of the USR were created: a submersible model deployable to a maximum depth of 300 m, and a watertight but not fully submersible model. Tests were performed on the USR in the laboratory using a data acquisition system to send single-frequency sinusoidal voltages directly to each component. These tests verified that the device operates as designed and performs as well as larger commercially available data acquisition systems, which are not suited for field use. On average, the designed gain values differed from the actual measured gain values by about 0.35 dB. A prototype of the device was used in a case study to measure blast pressures while investigating the effect of underwater rock blasting on juvenile Chinook salmon and rainbow trout. In the case study, maximum positive pressure from the blast was found to be significantly correlated with frequency of injury for individual fish. The case study also demonstrated that the device withstood operation in harsh environments, making it a valuable tool for collecting field measurements.

  14. Broadband focusing of underwater sound using a transparent pentamode lens.

    Science.gov (United States)

    Su, Xiaoshi; Norris, Andrew N; Cushing, Colby W; Haberman, Michael R; Wilson, Preston S

    2017-06-01

    An inhomogeneous acoustic metamaterial lens based on spatial variation of refractive index for broadband focusing of underwater sound is reported. The index gradient follows a modified hyperbolic secant profile designed to reduce aberration and suppress side lobes. The gradient index (GRIN) lens is comprised of transversely isotropic hexagonal microstructures with tunable quasi-static bulk modulus and mass density. In addition, the unit cells are impedance-matched to water and have in-plane shear modulus negligible compared to the effective bulk modulus. The flat GRIN lens is fabricated by cutting hexagonal centimeter scale hollow microstructures in aluminum plates, which are then stacked and sealed from the exterior water. Broadband focusing effects are observed within the homogenization regime of the lattice in both finite element simulations and underwater measurements (20-40 kHz). This design approach has potential applications in medical ultrasound imaging and underwater acoustic communications.

  15. Transducers and arrays for underwater sound

    CERN Document Server

    Butler, John L

    2016-01-01

    This improved and updated second edition covers the theory, development, and design of electro-acoustic transducers for underwater applications. This highly regarded text discusses the basics of piezoelectric and magnetostrictive transducers that are currently being used as well as promising new designs. It presents the basic acoustics as well as the specific acoustics data needed in transducer design and evaluation. A broad range of designs of projectors and hydrophones are described in detail along with methods of modeling, evaluation, and measurement. Analysis of projector and hydrophone transducer arrays, including the effects of mutual radiation impedance and numerical models for elements and arrays, are also covered. The book includes new advances in transducer design and transducer materials and has been completely reorganized to be suitable for use as a textbook, as well as a reference or handbook. The new edition contains updates to the first edition, end-of-chapter exercises, and solutions to select...

  16. Sources of underwater sound and their characterization

    NARCIS (Netherlands)

    Ainslie, M.A.; Jong, C.A.F. de

    2016-01-01

    Because of the history of sonar and sonar engineering, the concept of “source level” is widely used to characterize anthropogenic sound sources, but is it useful for sources other than sonar transmitters? The concept and applicability of source level are reviewed for sonar, air guns, explosions,

  17. Mapping Underwater Sound in the Dutch Part of the North Sea.

    Science.gov (United States)

    Sertlek, H Özkan; Aarts, Geert; Brasseur, Sophie; Slabbekoorn, Hans; ten Cate, Carel; von Benda-Beckmann, Alexander M; Ainslie, Michael A

    2016-01-01

    The European Union requires member states to achieve or maintain good environmental status for their marine territorial waters and explicitly mentions potentially adverse effects of underwater sound. In this study, we focused on producing maps of underwater sound from various natural and anthropogenic origins in the Dutch North Sea. The source properties and sound propagation are simulated by mathematical methods. These maps could be used to assess and predict large-scale effects on behavior and distribution of underwater marine life and therefore become a valuable tool in assessing and managing the impact of underwater sound on marine life.

  18. Acoustically sticky topographic metasurfaces for underwater sound absorption.

    Science.gov (United States)

    Lee, Hunki; Jung, Myungki; Kim, Minsoo; Shin, Ryung; Kang, Shinill; Ohm, Won-Suk; Kim, Yong Tae

    2018-03-01

    A class of metasurfaces for underwater sound absorption, based on a design principle that maximizes thermoviscous loss, is presented. When a sound meets a solid surface, it leaves a footprint in the form of thermoviscous boundary layers in which energy loss takes place. Considered to be a nuisance, this acoustic to vorticity/entropy mode conversion and the subsequent loss are often ignored in the existing designs of acoustic metamaterials and metasurfaces. The metasurface created is made of a series of topographic meta-atoms, i.e., intaglios and reliefs engraved directly on the solid object to be concealed. The metasurface is acoustically sticky in that it rather facilitates the conversion of the incident sound to vorticity and entropy modes, hence the thermoviscous loss, leading to the desired anechoic property. A prototype metasurface machined on a brass object is tested for its anechoicity, and shows a multitude of absorption peaks as large as unity in the 2-5 MHz range. Computations also indicate that a topographic metasurface is robust to hydrostatic pressure variation, a quality much sought-after in underwater applications.

  19. Mapping underwater sound in the dutch part of the North Sea

    NARCIS (Netherlands)

    Özkan Sertlek, H.; Aarts, Geert; Brasseur, Sophie; Slabbekoorn, Hans; Cate, ten Carel; Benda-Beckmann, von Alexander M.; Ainslie, Michael A.

    2016-01-01

    The European Union requires member states to achieve or maintain good environmental status for their marine territorial waters and explicitly mentions potentially adverse effects of underwater sound. In this study, we focused on producing maps of underwater sound from various natural and

  20. Mapping underwater sound in the Dutch part of the North Sea

    NARCIS (Netherlands)

    Sertlek, H.O.; Aarts, G.; Brasseur, S.; Slabbekoorn, H.; Cate, C. ten; Benda-Beckmann, A.M. von; Ainslie, M.A.

    2016-01-01

    The European Union requires member states to achieve or maintain good environmental status for their marine territorial waters and explicitly mentions potentially adverse effects of underwater sound. In this study, we focused on producing maps of underwater sound from various natural and

  1. Thin Fresnel zone plate lenses for focusing underwater sound

    Energy Technology Data Exchange (ETDEWEB)

    Calvo, David C., E-mail: david.calvo@nrl.navy.mil; Thangawng, Abel L.; Nicholas, Michael; Layman, Christopher N. [Acoustics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2015-07-06

    A Fresnel zone plate (FZP) lens of the Soret type creates a focus by constructive interference of waves diffracted through open annular zones in an opaque screen. For underwater sound below MHz frequencies, a large FZP that blocks sound using high-impedance, dense materials would have practical disadvantages. We experimentally and numerically investigate an alternative approach of creating a FZP with thin (0.4λ) acoustically opaque zones made of soft silicone rubber foam attached to a thin (0.1λ) transparent rubber substrate. An ultra-thin (0.0068λ) FZP that achieves higher gain is also proposed and simulated which uses low-volume fraction, bubble-like resonant air ring cavities to construct opaque zones. Laboratory measurements at 200 kHz indicate that the rubber foam can be accurately modeled as a lossy fluid with an acoustic impedance approximately 1/10 that of water. Measured focal gains up to 20 dB agree with theoretical predictions for normal and oblique incidence. The measured focal radius of 0.68λ (peak-to-null) agrees with the Rayleigh diffraction limit prediction of 0.61 λ/NA (NA = 0.88) for a low-aberration lens.

  2. Thin Fresnel zone plate lenses for focusing underwater sound

    Science.gov (United States)

    Calvo, David C.; Thangawng, Abel L.; Nicholas, Michael; Layman, Christopher N.

    2015-07-01

    A Fresnel zone plate (FZP) lens of the Soret type creates a focus by constructive interference of waves diffracted through open annular zones in an opaque screen. For underwater sound below MHz frequencies, a large FZP that blocks sound using high-impedance, dense materials would have practical disadvantages. We experimentally and numerically investigate an alternative approach of creating a FZP with thin (0.4λ) acoustically opaque zones made of soft silicone rubber foam attached to a thin (0.1λ) transparent rubber substrate. An ultra-thin (0.0068λ) FZP that achieves higher gain is also proposed and simulated which uses low-volume fraction, bubble-like resonant air ring cavities to construct opaque zones. Laboratory measurements at 200 kHz indicate that the rubber foam can be accurately modeled as a lossy fluid with an acoustic impedance approximately 1/10 that of water. Measured focal gains up to 20 dB agree with theoretical predictions for normal and oblique incidence. The measured focal radius of 0.68λ (peak-to-null) agrees with the Rayleigh diffraction limit prediction of 0.61 λ/NA (NA = 0.88) for a low-aberration lens.

  3. Thin Fresnel zone plate lenses for focusing underwater sound

    International Nuclear Information System (INIS)

    Calvo, David C.; Thangawng, Abel L.; Nicholas, Michael; Layman, Christopher N.

    2015-01-01

    A Fresnel zone plate (FZP) lens of the Soret type creates a focus by constructive interference of waves diffracted through open annular zones in an opaque screen. For underwater sound below MHz frequencies, a large FZP that blocks sound using high-impedance, dense materials would have practical disadvantages. We experimentally and numerically investigate an alternative approach of creating a FZP with thin (0.4λ) acoustically opaque zones made of soft silicone rubber foam attached to a thin (0.1λ) transparent rubber substrate. An ultra-thin (0.0068λ) FZP that achieves higher gain is also proposed and simulated which uses low-volume fraction, bubble-like resonant air ring cavities to construct opaque zones. Laboratory measurements at 200 kHz indicate that the rubber foam can be accurately modeled as a lossy fluid with an acoustic impedance approximately 1/10 that of water. Measured focal gains up to 20 dB agree with theoretical predictions for normal and oblique incidence. The measured focal radius of 0.68λ (peak-to-null) agrees with the Rayleigh diffraction limit prediction of 0.61 λ/NA (NA = 0.88) for a low-aberration lens

  4. Enhancement of acoustical performance of hollow tube sound absorber

    International Nuclear Information System (INIS)

    Putra, Azma; Khair, Fazlin Abd; Nor, Mohd Jailani Mohd

    2016-01-01

    This paper presents acoustical performance of hollow structures utilizing the recycled lollipop sticks as acoustic absorbers. The hollow cross section of the structures is arranged facing the sound incidence. The effects of different length of the sticks and air gap on the acoustical performance are studied. The absorption coefficient was measured using impedance tube method. Here it is found that improvement on the sound absorption performance is achieved by introducing natural kapok fiber inserted into the void between the hollow structures. Results reveal that by inserting the kapok fibers, both the absorption bandwidth and the absorption coefficient increase. For test sample backed by a rigid surface, best performance of sound absorption is obtained for fibers inserted at the front and back sides of the absorber. And for the case of test sample with air gap, this is achieved for fibers introduced only at the back side of the absorber.

  5. Aquatic Acoustic Metrics Interface Utility for Underwater Sound Monitoring and Analysis

    Science.gov (United States)

    Ren, Huiying; Halvorsen, Michele B.; Deng, Zhiqun Daniel; Carlson, Thomas J.

    2012-01-01

    Fishes and marine mammals may suffer a range of potential effects from exposure to intense underwater sound generated by anthropogenic activities such as pile driving, shipping, sonars, and underwater blasting. Several underwater sound recording (USR) devices have been built to acquire samples of the underwater sound generated by anthropogenic activities. Software becomes indispensable for processing and analyzing the audio files recorded by these USRs. In this paper, we provide a detailed description of a new software package, the Aquatic Acoustic Metrics Interface (AAMI), specifically designed for analysis of underwater sound recordings to provide data in metrics that facilitate evaluation of the potential impacts of the sound on aquatic animals. In addition to the basic functions, such as loading and editing audio files recorded by USRs and batch processing of sound files, the software utilizes recording system calibration data to compute important parameters in physical units. The software also facilitates comparison of the noise sound sample metrics with biological measures such as audiograms of the sensitivity of aquatic animals to the sound, integrating various components into a single analytical frame. The features of the AAMI software are discussed, and several case studies are presented to illustrate its functionality. PMID:22969353

  6. Aquatic Acoustic Metrics Interface Utility for Underwater Sound Monitoring and Analysis

    Directory of Open Access Journals (Sweden)

    Thomas J. Carlson

    2012-05-01

    Full Text Available Fishes and marine mammals may suffer a range of potential effects from exposure to intense underwater sound generated by anthropogenic activities such as pile driving, shipping, sonars, and underwater blasting. Several underwater sound recording (USR devices have been built to acquire samples of the underwater sound generated by anthropogenic activities. Software becomes indispensable for processing and analyzing the audio files recorded by these USRs. In this paper, we provide a detailed description of a new software package, the Aquatic Acoustic Metrics Interface (AAMI, specifically designed for analysis of underwater sound recordings to provide data in metrics that facilitate evaluation of the potential impacts of the sound on aquatic animals. In addition to the basic functions, such as loading and editing audio files recorded by USRs and batch processing of sound files, the software utilizes recording system calibration data to compute important parameters in physical units. The software also facilitates comparison of the noise sound sample metrics with biological measures such as audiograms of the sensitivity of aquatic animals to the sound, integrating various components into a single analytical frame. The features of the AAMI software are discussed, and several case studies are presented to illustrate its functionality.

  7. Effect of thermal-treatment sequence on sound absorbing and mechanical properties of porous sound-absorbing/thermal-insulating composites

    Directory of Open Access Journals (Sweden)

    Huang Chen-Hung

    2016-01-01

    Full Text Available Due to recent rapid commercial and industrial development, mechanical equipment is supplemented massively in the factory and thus mechanical operation causes noise which distresses living at home. In livelihood, neighborhood, transportation equipment, jobsite construction noises impact on quality of life not only factory noise. This study aims to preparation technique and property evaluation of porous sound-absorbing/thermal-insulating composites. Hollow three-dimensional crimp PET fibers blended with low-melting PET fibers were fabricated into hollow PET/low-melting PET nonwoven after opening, blending, carding, lapping and needle-bonding process. Then, hollow PET/low-melting PET nonwovens were laminated into sound-absorbing/thermal-insulating composites by changing sequence of needle-bonding and thermal-treatment. The optimal thermal-treated sequence was found by tensile strength, tearing strength, sound-absorbing coefficient and thermal conductivity coefficient tests of porous composites.

  8. Properties of sound attenuation around a two-dimensional underwater vehicle with a large cavitation number

    International Nuclear Information System (INIS)

    Ye Peng-Cheng; Pan Guang

    2015-01-01

    Due to the high speed of underwater vehicles, cavitation is generated inevitably along with the sound attenuation when the sound signal traverses through the cavity region around the underwater vehicle. The linear wave propagation is studied to obtain the influence of bubbly liquid on the acoustic wave propagation in the cavity region. The sound attenuation coefficient and the sound speed formula of the bubbly liquid are presented. Based on the sound attenuation coefficients with various vapor volume fractions, the attenuation of sound intensity is calculated under large cavitation number conditions. The result shows that the sound intensity attenuation is fairly small in a certain condition. Consequently, the intensity attenuation can be neglected in engineering. (paper)

  9. Captive Bottlenose Dolphins Do Discriminate Human-Made Sounds Both Underwater and in the Air

    Science.gov (United States)

    Lima, Alice; Sébilleau, Mélissa; Boye, Martin; Durand, Candice; Hausberger, Martine; Lemasson, Alban

    2018-01-01

    Bottlenose dolphins (Tursiops truncatus) spontaneously emit individual acoustic signals that identify them to group members. We tested whether these cetaceans could learn artificial individual sound cues played underwater and whether they would generalize this learning to airborne sounds. Dolphins are thought to perceive only underwater sounds and their training depends largely on visual signals. We investigated the behavioral responses of seven dolphins in a group to learned human-made individual sound cues, played underwater and in the air. Dolphins recognized their own sound cue after hearing it underwater as they immediately moved toward the source, whereas when it was airborne they gazed more at the source of their own sound cue but did not approach it. We hypothesize that they perhaps detected modifications of the sound induced by air or were confused by the novelty of the situation, but nevertheless recognized they were being “targeted.” They did not respond when hearing another group member’s cue in either situation. This study provides further evidence that dolphins respond to individual-specific sounds and that these marine mammals possess some capacity for processing airborne acoustic signals. PMID:29445350

  10. Simulation and Characteristics Analysis on Vibration and Sound Radiation Response for a Small Underwater Robot

    Directory of Open Access Journals (Sweden)

    Zhou Zhi

    2016-01-01

    Full Text Available An underwater robot is one of the important ocean equipment, and especially its stealth performance has influenced on the vitality in naval warfare. Structure radiation noise as the main source of underwater robot noise, so analysis on vibration and noise radiation is a topic of great concern. The way is used widely that based on fluid-solid coupling modal analysis combined with simulation on vibration and noise-radiation response in order to evaluate stealth performance of underwater structure. In the paper, firstly via finite element method and boundary element method, the modal frequencies and vibration modes of small underwater robot are calculated. Then the surface vibration displacements of underwater robot and the sound pressures of acoustic field under different frequency horizontal exciting force are obtained and analyzed. Lastly, through the analysis of the structural vibration and acoustic performance, the control strategies for structure bending vibration, acoustic radiation and structural acoustic design are proposed.

  11. Topological phononic states of underwater sound based on coupled ring resonators

    Energy Technology Data Exchange (ETDEWEB)

    He, Cheng; Li, Zheng; Ni, Xu; Sun, Xiao-Chen; Yu, Si-Yuan [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Lu, Ming-Hui, E-mail: luminghui@nju.edu.cn; Liu, Xiao-Ping; Chen, Yan-Feng [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2016-01-18

    We report a design of topological phononic states for underwater sound using arrays of acoustic coupled ring resonators. In each individual ring resonator, two degenerate acoustic modes, corresponding to clockwise and counter-clockwise propagation, are treated as opposite pseudospins. The gapless edge states arise in the bandgap resulting in protected pseudospin-dependent sound transportation, which is a phononic analogue of the quantum spin Hall effect. We also investigate the robustness of the topological sound state, suggesting that the observed pseudospin-dependent sound transportation remains unless the introduced defects facilitate coupling between the clockwise and counter-clockwise modes (in other words, the original mode degeneracy is broken). The topological engineering of sound transportation will certainly promise unique design for next generation of acoustic devices in sound guiding and switching, especially for underwater acoustic devices.

  12. Reducing Railway Noise with Porous Sound-Absorbing Concrete Slabs

    Directory of Open Access Journals (Sweden)

    Caiyou Zhao

    2014-01-01

    Full Text Available The effect of porous sound-absorbing concrete slabs on railway noise reduction is examined in this paper. First, the acoustical absorption coefficients of porous concrete materials with various aggregate types, gradations, fibre contents, and compaction indexes are measured in the laboratory. The laboratory results show that porous concrete that uses a composite of expanded perlite and slag as aggregate can not only obtain good acoustical absorption properties but also satisfy mechanical requirements. Also, the gradation of the combined aggregate has a significant effect on the acoustic absorption performance of the porous concrete, with an optimal aggregate gradation of 1~3 mm. Furthermore, the fibre content and compaction index affect both the strength and the acoustic absorption property of the porous concrete, with the optimum value of 0.3% and 1.6, respectively. Then, the findings from the laboratory studies are used to make porous sound-absorbing concrete slabs, which are applied in a test section. The measurements indicate that porous sound-absorbing concrete slabs can significantly reduce railway noise at different train speeds and that the amount of the noise reduction changes roughly linearly with speed when the train is traveling at less than 200 km/h. The maximum noise reduction is 4.05 dB at a speed of 200 km/h.

  13. Behavioural Response Thresholds in New Zealand Crab Megalopae to Ambient Underwater Sound

    Science.gov (United States)

    Stanley, Jenni A.; Radford, Craig A.; Jeffs, Andrew G.

    2011-01-01

    A small number of studies have demonstrated that settlement stage decapod crustaceans are able to detect and exhibit swimming, settlement and metamorphosis responses to ambient underwater sound emanating from coastal reefs. However, the intensity of the acoustic cue required to initiate the settlement and metamorphosis response, and therefore the potential range over which this acoustic cue may operate, is not known. The current study determined the behavioural response thresholds of four species of New Zealand brachyuran crab megalopae by exposing them to different intensity levels of broadcast reef sound recorded from their preferred settlement habitat and from an unfavourable settlement habitat. Megalopae of the rocky-reef crab, Leptograpsus variegatus, exhibited the lowest behavioural response threshold (highest sensitivity), with a significant reduction in time to metamorphosis (TTM) when exposed to underwater reef sound with an intensity of 90 dB re 1 µPa and greater (100, 126 and 135 dB re 1 µPa). Megalopae of the mud crab, Austrohelice crassa, which settle in soft sediment habitats, exhibited no response to any of the underwater reef sound levels. All reef associated species exposed to sound levels from an unfavourable settlement habitat showed no significant change in TTM, even at intensities that were similar to their preferred reef sound for which reductions in TTM were observed. These results indicated that megalopae were able to discern and respond selectively to habitat-specific acoustic cues. The settlement and metamorphosis behavioural response thresholds to levels of underwater reef sound determined in the current study of four species of crabs, enables preliminary estimation of the spatial range at which an acoustic settlement cue may be operating, from 5 m to 40 km depending on the species. Overall, these results indicate that underwater sound is likely to play a major role in influencing the spatial patterns of settlement of coastal crab

  14. Optimization of Sound Absorbers Number and Placement in an Enclosed Room by Finite Element Simulation

    Science.gov (United States)

    Lau, S. F.; Zainulabidin, M. H.; Yahya, M. N.; Zaman, I.; Azmir, N. A.; Madlan, M. A.; Ismon, M.; Kasron, M. Z.; Ismail, A. E.

    2017-10-01

    Giving a room proper acoustic treatment is both art and science. Acoustic design brings comfort in the built environment and reduces noise level by using sound absorbers. There is a need to give a room acoustic treatment by installing absorbers in order to decrease the reverberant sound. However, they are usually high in price which cost much for installation and there is no system to locate the optimum number and placement of sound absorbers. It would be a waste if the room is overly treated with absorbers or cause improper treatment if the room is treated with insufficient absorbers. This study aims to determine the amount of sound absorbers needed and optimum location of sound absorbers placement in order to reduce the overall sound pressure level in specified room by using ANSYS APDL software. The size of sound absorbers needed is found to be 11 m 2 by using Sabine equation and different unit sets of absorbers are applied on walls, each with the same total areas to investigate the best configurations. All three sets (single absorber, 11 absorbers and 44 absorbers) has successfully treating the room by reducing the overall sound pressure level. The greatest reduction in overall sound pressure level is that of 44 absorbers evenly distributed around the walls, which has reduced as much as 24.2 dB and the least effective configuration is single absorber whereby it has reduced the overall sound pressure level by 18.4 dB.

  15. The influence of underwater data transmission sounds on the displacement behaviour of captive harbour seals (Phoca vitulina)

    NARCIS (Netherlands)

    Kastelein, R.A.; Heul, S. van der; Verboom, W.C.; Triesscheijn, R.J.V.; Jennings, N.V.

    2006-01-01

    To prevent grounding of ships and collisions between ships in shallow coastal waters, an underwater data collection and communication network (ACME) using underwater sounds to encode and transmit data is currently under development. Marine mammals might be affected by ACME sounds since they may use

  16. Effects of locally resonant modes on underwater sound absorption in viscoelastic materials.

    Science.gov (United States)

    Wen, Jihong; Zhao, Honggang; Lv, Linmei; Yuan, Bo; Wang, Gang; Wen, Xisen

    2011-09-01

    Recently, by introducing locally resonant scatterers with spherical shape proposed in phononic crystals into design of underwater sound absorption materials, the low-frequency underwater sound absorption phenomenon induced by the localized resonances is observed. To reveal this absorption mechanism, the effect of the locally resonant mode on underwater sound absorption should be studied. In this paper, the finite element method, which is testified efficiently by comparing the calculation results with those of the layer multiple scattering method, is introduced to investigate the dynamic modes and the corresponding sound absorption of localized resonance. The relationship between the resonance modes described with the displacement contours of one unit cell and the corresponding absorption spectra is discussed in detail, which shows that the localized resonance leads to the absorption peak, and the mode conversion from longitudinal to transverse waves at the second absorption peak is more efficient than that at the first one. Finally, to show the modeling capability of FEM and investigate shape effects of locally resonant scatterers on underwater sound absorption, the absorption properties of viscoelastic materials containing locally resonant scatterers with ellipsoidal shape are discussed. © 2011 Acoustical Society of America

  17. Experimental Assessment of Underwater Radiated Sound of Different Ship Types

    NARCIS (Netherlands)

    Jansen, H.W.; Jong, C.A.F. de

    2015-01-01

    The aim of the SONIC project is to develop tools to investigate and mitigate the effects of underwater noise generated by shipping. One way to study the contribution of shipping noise to the background noise in the seas is to produce shipping noise maps. The SONIC project delivers the required

  18. Underwater sound due to a subsea high speed turbo compressor

    NARCIS (Netherlands)

    Binnerts, B.; Benda-Beckmann, A.M. von; Beek, P.J.G. van

    2014-01-01

    In the oil & gas industry there is a trend towards more subsea activities. To improve gas recovery from existing and new fields at greater depths, the produced gas will be compressed, processed and transported via subsea templates and underwater networks (pipelines, flexible risers, etc.). Besides

  19. Underwater sound scattering and absorption by a coated infinite plate with a distributed inhomogeneity.

    Science.gov (United States)

    Zhang, Yanni; Pan, Jie

    2013-04-01

    This paper concerns itself with the scattering and absorption of underwater incident sound by a coated infinite plate with an attached distributed inhomogeneity. Its objective is to determine if the distributed inhomogeneity can provide additional local reflection, such that it only increases the signal-to-noise ratio for a hydrophone detector placed on the inhomogeneity without significantly decreasing the overall sound absorption of the coated plate.

  20. Recycling ceramic industry wastes in sound absorbing materials

    Directory of Open Access Journals (Sweden)

    C. Arenas

    2016-10-01

    Full Text Available The scope of this investigation is to develop a material mainly composed (80% w/w of ceramic wastes that can be applied in the manufacture of road traffic noise reducing devices. The characterization of the product has been carried out attending to its acoustic, physical and mechanical properties, by measuring the sound absorption coefficient at normal incidence, the open void ratio, density and compressive strength. Since the sound absorbing behavior of a porous material is related to the size of the pores and the thickness of the specimen tested, the influence of the particle grain size of the ceramic waste and the thickness of the samples tested on the properties of the final product has been analyzed. The results obtained have been compared to a porous concrete made of crushed granite aggregate as a reference commercial material traditionally used in similar applications. Compositions with coarse particles showed greater sound absorption properties than compositions made with finer particles, besides presenting better sound absorption behavior than the reference porous concrete. Therefore, a ceramic waste-based porous concrete can be potentially recycled in the highway noise barriers field.

  1. Assessment of normal incidence absorption performance of sound absorbing materials

    Directory of Open Access Journals (Sweden)

    Farhad Forouharmajd

    2016-01-01

    Full Text Available Aims: The purpose of the present work was to consider the effect of different samples thicknesses on the acoustic absorption coefficient. Materials and Methods: An impedance tube was built with two microphones accordance to ISO-10534 and the American Society for Testing Materials-E1050 standards. For the measurement of absorption, the study was carried for 25 and 30 mm thicknesses of closed cell polyurethane foam, polystyrene, polyvinyl chloride (PVC, rubber, mineral wool, carpet, and glass samples. Measurements were performed by impedance tube and VA-lab4 software. Results: In carpet and mineral wool with more thickness, the absorption was increased but, the carpet with less thickness showed more sound absorption in the frequency range of 1500-3600 Hz. The peak of the absorption coefficient of 25 mm glass was 0.36 that the amount was reduced to 0.2 in the 30 mm thickness. Furthermore, the difference between the peak absorption of two thicknesses in polystyrene sample was equal to 0.29. In fact, polystyrene with less thickness had better sound absorption. The same situation was happened for glass in frequencies of below 4500 Hz with less thickness. Conclusion: Incident sound energy, which is not absorbed, must be reflected, transmitted, or dissipated. The porous materials had a higher absorption coefficient. Carpet and mineral wool samples had the highest absorption coefficient, but the materials such as polyurethane foam, PVC, and rubber had lower sound absorption.

  2. Monitoring programme for the Maasvlakte 2. Part III : The effects of underwater sound

    NARCIS (Netherlands)

    Heinis, F.; De Jong, C.; Ainslie, M.; Borst, W.; Vellinga, T.

    2013-01-01

    The Port of Rotterdam is expanding to meet the growing demand to accommodate large cargo vessels. The construction of Maasvlakte 2 (MV2) started in September 2008. One of the licensing conditions is the monitoring of the underwater sound produced during its construction, with an emphasis on the

  3. Monitoring Programme for the Maasvlakte 2, Part III - The Effects of Underwater Sound

    NARCIS (Netherlands)

    Heinis, F.; Jong, C.A.F. de; Ainslie, M.A.; Borst, W.; Vellinga, T.

    2013-01-01

    The Port of Rotterdam is expanding to meet the growing demand to accommodate large cargo vessels. The construction of Maasvlakte 2 (MV2) started in September 2008. One of the licensing conditions is the monitoring of the underwater sound produced during its construction, with an emphasis on the

  4. The Prediction of Sound Absorbing Coefficient for Multi-Layer Non-Woven

    OpenAIRE

    Un-Hwan Park; Jun-Hyeok Heo; In-Sung Lee; Tae-Hyeon Oh; Dae-Gyu Park

    2017-01-01

    Automotive interior material consisting of several material layers has the sound-absorbing function. It is difficult to predict sound absorbing coefficient because of several material layers. So, many experimental tunings are required to achieve the target of sound absorption. Therefore, while the car interior materials are developed, so much time and money is spent. In this study, we present a method to predict the sound absorbing performance of the material with multi-layer using physical p...

  5. Recycling Pig Slurry Solid Fraction Compost as a Sound Absorber

    Directory of Open Access Journals (Sweden)

    Niccolò Pampuro

    2018-01-01

    Full Text Available The aim of this investigation was to determine the physical and acoustical properties of compacts made from composted pig slurry solid fraction (SF in order to assess the potential to recycle this agricultural waste as a sound absorber. The compacts were obtained by compression. The physical parameters investigated were bulk density, durability, and particle size distribution. The acoustical features of the compacts were studied with an impedance tube device in order to verify the acoustic absorption coefficient. Two composts were prepared: pig SF compost without a bulking agent (SSFC and pig SF compost with wood chips as a bulking agent (WCC. The study’s results indicated that compost particles dimension played a key role in the physical and acoustical properties of the compacts: the smaller the particles, the higher the physical and acoustical properties of the compacts. The densification process increased the bulk density of the investigated composts up to 690 kg m−3 for SSFC and 660 kg m−3 for WWC, with, respectively, medium (77.9% and low (66.5% durability. The addition of woody bulking agent significantly reduced the absorption coefficient: the best results, in terms of potential use as a sound absorber, were observed for compacts made from composted pig slurry solid fraction without the addition of wood chips.

  6. Sound transmission of sandwich beams with the dynamic vibration absorbers

    Directory of Open Access Journals (Sweden)

    Bohdan Diveyev

    2015-07-01

    Full Text Available This study aims to predict the sound transmission properties of composite layered beams structures with the system of dynamic vibration absorbers (DVA’s. The effective stiffness constants of equivalent to lamina Timoshenko beam and their damping properties have been determined by using a procedure based on multi-level numerical schemes and eigen-frequencies comparison. The strategy of an anisotropic beam to the Timoshenko beam seem to be such: the raw of models can be applied at different vibration or static conditions of the plate by a suitable analytical ore approximation method, research of sensitiveness in relation to the parameters of fixing and material anisotropy, numerical experiments on identification of elastic modules, practical module identification by exploring different schemes of experimental setup and, finally, posterior analysis of identification quality. The combined method of identification was proposed on the basis of the simultaneous use of information on a homogeneous beam and beam with an internal layer, with identical mechanical properties to the homogeneous beam. Numerical evaluations obtained for the vibration of the equivalent Timoshenko beam have been used to determine the sound transmission properties of laminated composite beams with the system of DVA’s. The optimization of beams-DVA’s system sound absorption properties is performed in the low frequency range.

  7. Optimal design of sound absorbing systems with microperforated panels

    Science.gov (United States)

    Kim, Nicholas Nakjoo

    As the development of technology makes economic prosperity and life more convenient, people now desire a higher quality of life. This quality of life is based not only on the convenience in their life but also on clean and eco-friendly environments. To meet that requirement, much research is being performed in many areas of eco-friendly technology, such as renewable energy, biodegradable content, and batteries for electronic vehicles. This tendency is also obvious in the acoustics area, where there are continuing attempts to replace fiber-glass sound absorbers with fiber-free materials. The combination of microperfoated panels (MPP) (one of the fiber-free sound absorbing materials), usually in the form of a thin panel with small holes, and an air backing may be one of the preferred solutions. These panels can be designed in many ways, and usually feature many small (sub-millimeter) holes and typically surface porosities on the order of 1 percent. The detailed acoustical properties of MPPs depend on their hole shape, the hole diameter, the thickness of the panel, the overall porosity of the perforated film, the film's mass per unit area, and the depth of the backing air cavity. Together, these parameters control the absorption peak location and the magnitude of the absorption coefficient (and the magnitude of the transmission loss in barrier applications). By an appropriate choice of these parameters good absorption performance can be achieved in a frequency range one or two octaves wide. That kind of solution may be adequate when it is necessary to control sound only in a specified frequency range (in the speech interference range, for example). However, in order to provide appropriate noise control solutions over a broader range of frequencies, it is necessary to design systems featuring multiple-layers of MPPs, thus creating what amounts to a multi-degree-of-freedom system and so expanding the range over which good absorption can be obtained. In this research

  8. Underwater sound from vessel traffic reduces the effective communication range in Atlantic cod and haddock.

    Science.gov (United States)

    Stanley, Jenni A; Van Parijs, Sofie M; Hatch, Leila T

    2017-11-07

    Stellwagen Bank National Marine Sanctuary is located in Massachusetts Bay off the densely populated northeast coast of the United States; subsequently, the marine inhabitants of the area are exposed to elevated levels of anthropogenic underwater sound, particularly due to commercial shipping. The current study investigated the alteration of estimated effective communication spaces at three spawning locations for populations of the commercially and ecologically important fishes, Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus). Both the ambient sound pressure levels and the estimated effective vocalization radii, estimated through spherical spreading models, fluctuated dramatically during the three-month recording periods. Increases in sound pressure level appeared to be largely driven by large vessel activity, and accordingly exhibited a significant positive correlation with the number of Automatic Identification System tracked vessels at the two of the three sites. The near constant high levels of low frequency sound and consequential reduction in the communication space observed at these recording sites during times of high vocalization activity raises significant concerns that communication between conspecifics may be compromised during critical biological periods. This study takes the first steps in evaluating these animals' communication spaces and alteration of these spaces due to anthropogenic underwater sound.

  9. Experimental findings on the underwater measurements uncertainty of speed of sound and the alignment system

    Science.gov (United States)

    Santos, T. Q.; Alvarenga, A. V.; Oliveira, D. P.; Mayworm, R. C.; Souza, R. M.; Costa-Félix, R. P. B.

    2016-07-01

    Speed of sound is an important quantity to characterize reference materials for ultrasonic applications, for instance. The alignment between the transducer and the test body is an key activity in order to perform reliable and consistent measurement. The aim of this work is to evaluate the influence of the alignment system to the expanded uncertainty of such measurement. A stainless steel cylinder was previously calibrated on an out of water system typically used for calibration of non-destructive blocks. Afterwards, the cylinder was calibrated underwater with two distinct alignment system: fixed and mobile. The values were statistically compared to the out-of-water measurement, considered the golden standard for such application. For both alignment systems, the normalized error was less than 0.8, leading to conclude that the both measurement system (under and out-of-water) do not diverge significantly. The gold standard uncertainty was 2.7 m-s-1, whilst the fixed underwater system resulted in 13 m-s-1, and the mobile alignment system achieved 6.6 m-s-1. After the validation of the underwater system for speed of sound measurement, it will be applied to certify Encapsulated Tissue Mimicking Material as a reference material for biotechnology application.

  10. Oyster larvae settle in response to habitat-associated underwater sounds.

    Science.gov (United States)

    Lillis, Ashlee; Eggleston, David B; Bohnenstiehl, DelWayne R

    2013-01-01

    Following a planktonic dispersal period of days to months, the larvae of benthic marine organisms must locate suitable seafloor habitat in which to settle and metamorphose. For animals that are sessile or sedentary as adults, settlement onto substrates that are adequate for survival and reproduction is particularly critical, yet represents a challenge since patchily distributed settlement sites may be difficult to find along a coast or within an estuary. Recent studies have demonstrated that the underwater soundscape, the distinct sounds that emanate from habitats and contain information about their biological and physical characteristics, may serve as broad-scale environmental cue for marine larvae to find satisfactory settlement sites. Here, we contrast the acoustic characteristics of oyster reef and off-reef soft bottoms, and investigate the effect of habitat-associated estuarine sound on the settlement patterns of an economically and ecologically important reef-building bivalve, the Eastern oyster (Crassostrea virginica). Subtidal oyster reefs in coastal North Carolina, USA show distinct acoustic signatures compared to adjacent off-reef soft bottom habitats, characterized by consistently higher levels of sound in the 1.5-20 kHz range. Manipulative laboratory playback experiments found increased settlement in larval oyster cultures exposed to oyster reef sound compared to unstructured soft bottom sound or no sound treatments. In field experiments, ambient reef sound produced higher levels of oyster settlement in larval cultures than did off-reef sound treatments. The results suggest that oyster larvae have the ability to respond to sounds indicative of optimal settlement sites, and this is the first evidence that habitat-related differences in estuarine sounds influence the settlement of a mollusk. Habitat-specific sound characteristics may represent an important settlement and habitat selection cue for estuarine invertebrates and could play a role in driving

  11. Oyster larvae settle in response to habitat-associated underwater sounds.

    Directory of Open Access Journals (Sweden)

    Ashlee Lillis

    Full Text Available Following a planktonic dispersal period of days to months, the larvae of benthic marine organisms must locate suitable seafloor habitat in which to settle and metamorphose. For animals that are sessile or sedentary as adults, settlement onto substrates that are adequate for survival and reproduction is particularly critical, yet represents a challenge since patchily distributed settlement sites may be difficult to find along a coast or within an estuary. Recent studies have demonstrated that the underwater soundscape, the distinct sounds that emanate from habitats and contain information about their biological and physical characteristics, may serve as broad-scale environmental cue for marine larvae to find satisfactory settlement sites. Here, we contrast the acoustic characteristics of oyster reef and off-reef soft bottoms, and investigate the effect of habitat-associated estuarine sound on the settlement patterns of an economically and ecologically important reef-building bivalve, the Eastern oyster (Crassostrea virginica. Subtidal oyster reefs in coastal North Carolina, USA show distinct acoustic signatures compared to adjacent off-reef soft bottom habitats, characterized by consistently higher levels of sound in the 1.5-20 kHz range. Manipulative laboratory playback experiments found increased settlement in larval oyster cultures exposed to oyster reef sound compared to unstructured soft bottom sound or no sound treatments. In field experiments, ambient reef sound produced higher levels of oyster settlement in larval cultures than did off-reef sound treatments. The results suggest that oyster larvae have the ability to respond to sounds indicative of optimal settlement sites, and this is the first evidence that habitat-related differences in estuarine sounds influence the settlement of a mollusk. Habitat-specific sound characteristics may represent an important settlement and habitat selection cue for estuarine invertebrates and could play a

  12. Repellence Effect of the New Sound for Underwater Speaker of Hydrofoil

    Directory of Open Access Journals (Sweden)

    Tatsunori Nakashima

    2015-06-01

    Full Text Available In order to prevent hydrofoil colliding with cetaceans, the underwater speaker (UWS has been installed to repel cetaceans. Yamada et al. (2012 analyzed and devised the UWS sound as it fits the cetaceans' acoustic properties to prevent the collision furthermore. The new UWS sound was devised and synthesized by Yamada et al. (2015 with expectation of avoiding collision with large cetaceans (Patent applied for, JP2014-171411. In this research project, the new UWS sound was investigated by the playback experiment on humpback whale (Megaptera novaeangliae and by sighting survey in the actual hydrofoil shipping service route. As a result, a physiological and behavioral change of the humpback whale was observed in the playback experiment of the new UWS sound, and the chance of hydrofoil encountering cetaceans of the new UWS sound was smaller than that of the previous UWS sound. Therefore, the improvement of the new UWS sound was confirmed. Lastly, we wish this research project would contribute toward the safer cruise of hydrofoil in the future.

  13. Underwater sound scattering and absorption by a coated infinite plate with attached periodically located inhomogeneities.

    Science.gov (United States)

    Zhang, Yanni; Huang, Hai; Zheng, Jing; Pan, Jie

    2015-11-01

    This paper extends previous work of Zhang and Pan [J. Acoust. Soc. Am. 133(4), 2082-2096 (2013)] on sound scattering and absorption by an underwater coated plate with a single attached distributed-inhomogeneity to that with periodically located distributed-inhomogeneities. A comparison is made among cases of a plate without inhomogeneities, a plate with inhomogeneities, and one with inhomogeneities ignoring the mutual coupling. Results show that coupling of the structural waves scattered by the inhomogeneities plays an important role in modifying the sound absorption and scattering of surface sound pressure, especially at low frequencies and/or the resonance frequencies of the trapped modes of the plate. The sound absorption of the plate is dependent on the distance between the adjacent inhomogeneities, the length of the inhomogeneity, and the angle of the incident sound. On the surface of the inhomogeneities, the scattered/total sound pressure is generally enhanced. On the surface in between the inhomogeneities, the pressure is also enhanced at low frequencies but is nearly unchanged at higher frequencies. Results also show that the coupling-induced variation of scattered/total pressure is significant only at the resonance frequencies of the global modes and trapped modes. The surface normal velocity is presented to explain the coupling-induced variations in the vibration and pressure fields.

  14. Underwater sound radiation from an elastically coated plate with an embedded and distributed inhomogeneity.

    Science.gov (United States)

    Zhang, Yanni; Pan, Jie

    2015-05-01

    This paper studies the effects of an embedded and distributed inhomogeneity on the underwater sound radiation from an elastically coated plate. Embedding a signal conditioning plate (SCP) in the coating material provides an extra parameter for controlling the sound radiation of the plate, as compared with the previous design with an SCP on the coating surface [Y. Zhang and J. Pan, J. Acoust. Soc. Am. 133(1), 173-185 (2013)]. For such a configuration, the vibration and sound responses of the coated plate to a point force excitation are described by three coupled Fredholm integral equations of the second kind. Its acoustical properties are examined by comparing the radiation powers from plates without an SCP, with a surface SCP, and with an embedded SCP. The differences in the sound powers are explained through resonance and scattering caused by the interaction of the embedded SCP with structural waves. The effects of the depth of the embedded SCP in the coating material on the sound radiation properties of the plate are discussed in detail.

  15. Producing of Impedance Tube for Measurement of Acoustic Absorption Coefficient of Some Sound Absorber Materials

    Directory of Open Access Journals (Sweden)

    R. Golmohammadi

    2008-04-01

    Full Text Available Introduction & Objective: Noise is one of the most important harmful agents in work environment. In spit of industrial improvements, exposure with over permissible limit of noise is counted as one of the health complication of workers. In Iran, do not exact information of the absorption coefficient of acoustic materials. Iranian manufacturer have not laboratory for measured of sound absorbance of their products, therefore using of sound absorber is limited for noise control in industrial and non industrial constructions. The goal of this study was to design an impedance tube based on pressure method for measurement of the sound absorption coefficient of acoustic materials.Materials & Methods: In this study designing of measuring system and method of calculation of sound absorption based on a available equipment and relatively easy for measurement of the sound absorption coefficient related to ISO10534-1 was performed. Measuring system consist of heavy asbestos tube, a pure tone sound generator, calibrated sound level meter for measuring of some commonly of sound absorber materials was used. Results: In this study sound absorption coefficient of 23 types of available acoustic material in Iran was tested. Reliability of results by three repeat of measurement was tested. Results showed that the standard deviation of sound absorption coefficient of study materials was smaller than .Conclusion: The present study performed a necessary technology of designing and producing of impedance tube for determining of acoustical materials absorption coefficient in Iran.

  16. Sound absorption effects in a rectangular enclosure with the foamed aluminum sheet absorber

    International Nuclear Information System (INIS)

    Oh, Jae Eung; Chung, Jin Tai; Kim, Sang Hun; Chung, Kyung Ryul

    1998-01-01

    For the purpose of finding out the optimal thickness of sound absorber and the sound absorption effects due to the selected thickness at an interested frequency range, the analytical study identifies the interior and exterior sound field characteristics of a rectangular enclosure with foamed aluminum lining and the experimental verification is performed with random noise input. By using a two-microphone impedance tube, we measure experimentally the absorption coefficient and the impedance of simple sound absorbing materials. Measured acoustical parameters of the test samples are applied to the theoretical analysis to predict sound pressure field in the cavity. The sound absorption effects from measurements are compared to predicted ones in both cases with and without foamed aluminum lining in the cavity of the rectangular enclosure

  17. Broadband transmission noise reduction of smart panels featuring piezoelectric shunt circuits and sound-absorbing material.

    Science.gov (United States)

    Kim, Jaehwan; Lee, Joong-Kuen

    2002-09-01

    The possibility of a broadband noise reduction of piezoelectric smart panels is experimentally studied. A piezoelectric smart panel is basically a plate structure on which piezoelectric patches with electrical shunt circuits are mounted and sound-absorbing material is bonded on the surface of the structure. Sound-absorbing material can absorb the sound transmitted at the midfrequency region effectively while the use of piezoelectric shunt damping can reduce the transmission at resonance frequencies of the panel structure. To be able to reduce the sound transmission at low panel resonance frequencies, piezoelectric damping using the measured electrical impedance model is adopted. A resonant shunt circuit for piezoelectric shunt damping is composed of resistor and inductor in series, and they are determined by maximizing the dissipated energy through the circuit. The transmitted noise-reduction performance of smart panels is tested in an acoustic tunnel. The tunnel is a square cross-sectional tube and a loudspeaker is mounted at one side of the tube as a sound source. Panels are mounted in the middle of the tunnel and the transmitted sound pressure across panels is measured. When an absorbing material is bonded on a single plate, a remarkable transmitted noise reduction in the midfrequency region is observed except for the fundamental resonance frequency of the plate. By enabling the piezoelectric shunt damping, noise reduction is achieved at the resonance frequency as well. Piezoelectric smart panels incorporating passive absorbing material and piezoelectric shunt damping is a promising technology for noise reduction over a broadband of frequencies.

  18. Absorption of oblique incidence sound by a finite micro-perforated panel absorber.

    Science.gov (United States)

    Yang, Cheng; Cheng, Li; Pan, Jie

    2013-01-01

    In this paper, a theoretical model of a micro-perforated panel (MPP) backed by a finite cavity and flush-mounted in an infinite baffle is developed and its performance in terms of sound absorption is analyzed. The model allows an oblique incidence sound impinging upon the MPP absorber. The simplified Rayleigh integral method, thin plate theory and the acoustical impedance of the MPP are used to calculate the sound energy absorbed by the MPP's surface. Results show that the absorption coefficient of the absorber is a function of angle and frequency of the incident sound, and is controlled by the coupling between the MPP and the acoustical modes in the back cavity. In particular, grazing modes can be induced in the cavity by sound with an oblique angle of incidence, which may result in peak sound absorptions at the natural frequencies of the modes. The mechanism involved is used to explain the absorption properties of the MPP absorber for a diffuse incidence of sound.

  19. Underwater sound emissions and effects of the pile driving of the OWEZ windfarm facility near Egmond aan Zee (Tconstruct)

    NARCIS (Netherlands)

    Haan, de D.; Burggraaf, D.; Ybema, M.S.; Hille Ris Lambers, R.

    2007-01-01

    The aim of this part of the Monitoring and Evaluation Program NSW (MEP-NSW), i.e. “acoustic measurements”, is to measure and analyze underwater sound emissions from the construction of the OWEZ wind farm and to investigate the effects to marine animals (in particular fish, harbour porpoises and

  20. Semi-active control of piezoelectric coating's underwater sound absorption by combining design of the shunt impedances

    Science.gov (United States)

    Sun, Yang; Li, Zhaohui; Huang, Aigen; Li, Qihu

    2015-10-01

    Piezoelectric shunt damping technology has been applied in the field of underwater sound absorption in recent years. In order to achieve broadband echo reduction, semi-active control of sound absorption of multi-layered piezoelectric coating by shunt damping is significant. In this paper, a practical method is proposed to control the underwater sound absorption coefficients of piezoelectric coating layers by combining design of the shunt impedance that allows certain sound absorption coefficients at setting frequencies. A one-dimensional electro-acoustic model of the piezoelectric coating and the backing is established based on the Mason equivalent circuit theory. First, the shunt impedance of the coating is derived under the constraint of sound absorption coefficient at one frequency. Then, taking the 1-3 piezoelectric composite coating as an example, the sound absorption properties of the coating shunted to the designed shunt impedance are investigated. Next, on the basis of that, an iterative method for two constrained frequencies and an optimizing algorithm for multiple constrained frequencies are provided for combining design of the shunt impedances. At last, an experimental sample with four piezoelectric material layers is manufactured, of which the sound absorption coefficients are measured in an impedance tube. The experimental results show good agreement with the finite element simulation results. It is proved that a serial R-L circuit can control the peak frequency, maximum and bandwidth of the sound absorption coefficient and the combining R-L circuits shunted to multiple layers can control the sound absorption coefficients at multiple frequencies.

  1. The low-frequency sound power measuring technique for an underwater source in a non-anechoic tank

    Science.gov (United States)

    Zhang, Yi-Ming; Tang, Rui; Li, Qi; Shang, Da-Jing

    2018-03-01

    In order to determine the radiated sound power of an underwater source below the Schroeder cut-off frequency in a non-anechoic tank, a low-frequency extension measuring technique is proposed. This technique is based on a unique relationship between the transmission characteristics of the enclosed field and those of the free field, which can be obtained as a correction term based on previous measurements of a known simple source. The radiated sound power of an unknown underwater source in the free field can thereby be obtained accurately from measurements in a non-anechoic tank. To verify the validity of the proposed technique, a mathematical model of the enclosed field is established using normal-mode theory, and the relationship between the transmission characteristics of the enclosed and free fields is obtained. The radiated sound power of an underwater transducer source is tested in a glass tank using the proposed low-frequency extension measuring technique. Compared with the free field, the radiated sound power level of the narrowband spectrum deviation is found to be less than 3 dB, and the 1/3 octave spectrum deviation is found to be less than 1 dB. The proposed testing technique can be used not only to extend the low-frequency applications of non-anechoic tanks, but also for measurement of radiated sound power from complicated sources in non-anechoic tanks.

  2. Underwater sounds near a fuel receiving facility in western Hong Kong: relevance to dolphins.

    Science.gov (United States)

    Würsig, B; Greene, C R

    2002-08-01

    Western Hong Kong is home to two species of marine mammals: Indo-Pacific humpbacked dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides). Both are threatened in many parts of their range in southeast Asia [for example, International Biological Research Institute Reports 9 (1997), 41; Asian Marine Biology 14 (1997) 111]. In 1998, when the new Hong Kong International Airport opened in western Hong Kong, small tankers (about 100 m long, cargo capacity about 6300 metric tons) began delivering fuel to the Aviation Fuel Receiving Facility (AFRF) just off Sha Chau Island, north of the airport. Calibrated sound recordings were taken over a 4-day period from a quiet, anchored boat at distances 80-2000 m from aviation fuel delivery activities at the AFRF. From the recordings, 143 sections were selected for analysis. Narrowband spectral densities on the sound pressures were computed, and one-third octave band levels were derived for center frequencies from 10 to 16,000 Hz. Broadband levels, viz. 10-20,000 Hz. were also computed. The results showed that the Sha Chau area is normally noisy underwater, with the lowest broadband levels measured corresponding to those expected during a storm at sea (sea state 6). This background noise is believed to come largely from heavy vessel traffic in the Urmston Road to the north and east of Sha Chau and from vessels in the Pearl River Estuary to the West. The sound levels from the AFRF tankers are comparable to the levels measured from similar- and smaller-sized supply vessels supporting offshore oil exploration. The strongest sounds recorded were from a tanker leaving the AFRF at distance 100 m from the hydrophone, for which the one-third octave band level at 100 Hz was 141 dB re 1 microPa (spectrum level 127 dB re 1 microPa2/Hz) and the 10-20,000 Hz broadband level was 146 dB. At distances of 100 m or more and frequencies above 300 Hz, the one-third octave band levels were less than 130 dB (spectrum level 111 dB re

  3. Preparation of steel slag porous sound-absorbing material using coal powder as pore former.

    Science.gov (United States)

    Sun, Peng; Guo, Zhancheng

    2015-10-01

    The aim of the study was to prepare a porous sound-absorbing material using steel slag and fly ash as the main raw material, with coal powder and sodium silicate used as a pore former and binder respectively. The influence of the experimental conditions such as the ratio of fly ash, sintering temperature, sintering time, and porosity regulation on the performance of the porous sound-absorbing material was investigated. The results showed that the specimens prepared by this method had high sound absorption performance and good mechanical properties, and the noise reduction coefficient and compressive strength could reach 0.50 and 6.5MPa, respectively. The compressive strength increased when the dosage of fly ash and sintering temperature were raised. The noise reduction coefficient decreased with increasing ratio of fly ash and reducing pore former, and first increased and then decreased with the increase of sintering temperature and time. The optimum preparation conditions for the porous sound-absorbing material were a proportion of fly ash of 50% (wt.%), percentage of coal powder of 30% (wt.%), sintering temperature of 1130°C, and sintering time of 6.0hr, which were determined by analyzing the properties of the sound-absorbing material. Copyright © 2015. Published by Elsevier B.V.

  4. Comparison of sound absorbing performances of copper foam and iron foam with the same parameters

    Science.gov (United States)

    Yang, X. C.; Shen, X. M.; Xu, P. J.; Zhang, X. N.; Bai, P. F.; Peng, K.; Yin, Q.; Wang, D.

    2018-01-01

    Sound absorbing performances of the copper foam and the iron foam with the same parameters were investigated by the AWA6128A detector according to standing wave method. Two modes were investigated, which included the pure metal foam mode and the combination mode with the settled thickness of metal foam. In order to legibly compare the sound absorbing coefficients of the two metal foams, the detected sound frequency points were divided into the low frequency range (100 Hz ~ 1000 Hz), the middle frequency range (1000 Hz ~ 3200 Hz), and the high frequency range (3500 Hz ~ 6000 Hz). Sound absorbing performances of the two metal foams in the two modes were discussed within the three frequency ranges in detail. It would be calculated that the average sound absorbing coefficients of copper foam in the pure metal foam mode were 12.6%, 22.7%, 34.6%, 43.6%, 51.1%, and 56.2% when the thickness was 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm. meanwhile, in the combination mode, the average sound absorbing coefficients of copper foam with the thickness of 10 mm were 30.6%, 34.8%, 36.3%, and 35.8% when the cavity was 5 mm, 10 mm, 15 mm, and 20 mm. In addition, those of iron foam in the pure metal foam mode were 13.4%, 20.1%, 34.4%, 43.1%, 49.6%, and 56.1%, and in the combination mode were 25.6%, 30.5%, 34.3%, and 33.4%.

  5. Underwater sound radiation from an elastically coated plate with a discontinuity introduced by a signal conditioning plate.

    Science.gov (United States)

    Zhang, Yanni; Pan, Jie

    2013-01-01

    Underwater structural sound radiation and reflection can be reduced by adding an elastic coating to a structure. To increase the signal-to-noise ratio of a detecting hydrophone placed in front of the coating, a signal conditioning plate (SCP) of finite size placed between the coating and the hydrophone is proposed to increase the local reflection of incoming sound. This paper studies the effects of a SCP as a distributed discontinuity on the general properties of the sound radiation of a coated plate. The discontinuity introduced by the SCP changes the vibration and radiated sound power of the coated plate by scattering and reflecting structural waves in the coating. The trapped modal response of the structural waves is also observed and found to be responsible for the increase of sound and vibration of the plate at the corresponding resonance frequencies.

  6. Sound energy absorbance characteristics of cartilage grafts used in type 1 tympanoplasty.

    Science.gov (United States)

    Yüksel Aslıer, Nesibe Gül; Gürkan, Selhan; Aslıer, Mustafa; Kirkim, Günay; Güneri, Enis Alpin; Ikiz, Ahmet Ömer

    2018-03-15

    The purpose of this prospective case-control study is to evaluate the sound energy absorbance characteristics of cartilage grafts in patients, who have undergone type 1 cartilage tympanoplasty. Thirty-four operated ears of 32 patients and 70 ears of 35 control subjects were included. Differences of pure-tone audiometry thresholds and wideband ambient-pressure absorbance ratios with respect to the graft material, graft thickness, cartilage surface area ratio and elapsed time after surgery were analyzed. Receiver operating characteristics curve was generated to detect the absorbance level at which the reconstructed tympanic membrane behaves as 'near-normal tympanic membrane'. In the surgical group, wideband energy absorbance ratios at all 1/2-octave band frequencies were significantly worse than normal ears. Energy absorbance ratios at 2000 and 2828Hz frequencies were higher in patients with tragal cartilage grafts. Higher absorbance ratios at 250-750Hz range were obtained in patients with 400μm cartilage graft thickness, <50% cartilage surface area ratio and ≥5 years since surgery. A multivariate generalized linear model revealed common effects of the independent variables at 8000Hz. The receiver operating characteristics analysis generated a cut-off level of 63.20% of sound energy absorbance at 1400Hz with 83% sensitivity and 88% specificity. Even though no differences in hearing thresholds were observed; graft material, graft thickness, cartilage surface area ratio and elapsed time after surgery affected the course of sound energy absorbance after type 1 cartilage tympanoplasty as evidenced by wideband tympanometry. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Risk mapping for sensitive species to underwater anthropogenic sound emissions: model development and validation in two Mediterranean areas.

    Science.gov (United States)

    Azzellino, A; Lanfredi, C; D'Amico, A; Pavan, G; Podestà, M; Haun, J

    2011-01-01

    Recent observations of cetacean mass strandings, coincident with anthropogenic sounds emissions, have raised concerns on the potential environmental impact of underwater noise. Cuvier's beaked whale (Ziphius cavirostris) was reported in all the cited stranding events. Within the NATO Marine Mammal Risk Mitigation project (MMRM), multiple interdisciplinary sea trials have been conducted in the Mediterranean Sea with the objective of developing tools and procedures to mitigate the impact of underwater sound emissions. During these cruises, visual observations, passive acoustic detections and environmental data were collected. The aim of this study was to evaluate "a priori" predictions of Cuvier's beaked whale presence in the Alboran Sea, using models developed in the Ligurian Sea that employ bathymetric and chlorophyll features as predictors. The accuracy of these predictions was found adequate and elements are given to account for the uncertainties associated to the use of models developed in areas different from their calibration site. Copyright © 2011 Elsevier Ltd. All rights reserved.

  8. Ultrathin multi-slit metamaterial as excellent sound absorber: Influence of micro-structure

    Science.gov (United States)

    Ren, S. W.; Meng, H.; Xin, F. X.; Lu, T. J.

    2016-01-01

    An ultrathin (subwavelength) hierarchy multi-slit metamaterial with simultaneous negative effective density and negative compressibility is proposed to absorb sound over a wide frequency range. Different from conventional acoustic metamaterials having only negative real parts of acoustic parameters, the imaginary parts of effective density and compressibility are both negative for the proposed metamaterial, which result in superior viscous and thermal dissipation of sound energy. By combining the slit theory of sound absorption with the double porosity theory for porous media, a theoretical model is developed to investigate the sound absorption performance of the metamaterial. To verify the model, a finite element model is established to calculate the effective density, compressibility, and sound absorption of the metamaterial. It is theoretically and numerically confirmed that, upon introducing micro-slits into the meso-slits matrix, the multi-slit metamaterial possesses indeed negative imaginary parts of effective density and compressibility. The influence of micro-slits on the acoustical performance of the metamaterial is analyzed in the context of its specific surface area and static flow resistivity. This work shows great potential of multi-slit metamaterials in noise control applications that require both small volume and small weight of sound-absorbing materials.

  9. Single-channel labyrinthine metasurfaces as perfect sound absorbers with tunable bandwidth

    Science.gov (United States)

    Liu, Liu; Chang, Huiting; Zhang, Chi; Hu, Xinhua

    2017-08-01

    Perfect sound absorbers with a deep-subwavelength thickness are important to applications such as noise reduction and sound detection. But their absorption bandwidths are usually narrow and difficult to adjust. A recent solution for this problem relies on multiple-resonator metasurfaces, which are hard to fabricate. Here, we report on the design, fabrication, and characterization of a single-channel labyrinthine metasurface, which allows total sound absorption at resonant frequency when appropriate amounts of porous media (or critical sound losses) are introduced in the channels. The absorption bandwidth can be tuned by changing the cross-sectional areas of channels. A tradeoff is found between the absorption bandwidth and the metasurface thickness. However, large tunability in the relative absorption bandwidth (from 17% to 121%) is still attainable by such metasurfaces with a deep-subwavelength thickness (0.03-0.13λ).

  10. Dolphin Sounds-Inspired Covert Underwater Acoustic Communication and Micro-Modem

    OpenAIRE

    Gang Qiao; Yunjiang Zhao; Songzuo Liu; Muhammad Bilal

    2017-01-01

    A novel portable underwater acoustic modem is proposed in this paper for covert communication between divers or underwater unmanned vehicles (UUVs) and divers at a short distance. For the first time, real dolphin calls are used in the modem to realize biologically inspired Covert Underwater Acoustic Communication (CUAC). A variety of dolphin whistles and clicks stored in an SD card inside the modem helps to realize different biomimetic CUAC algorithms based on the specified covert scenario. I...

  11. Hybrid waste filler filled bio-polymer foam composites for sound absorbent materials

    Science.gov (United States)

    Rus, Anika Zafiah M.; Azahari, M. Shafiq M.; Kormin, Shaharuddin; Soon, Leong Bong; Zaliran, M. Taufiq; Ahraz Sadrina M. F., L.

    2017-09-01

    Sound absorption materials are one of the major requirements in many industries with regards to the sound insulation developed should be efficient to reduce sound. This is also important to contribute in economically ways of producing sound absorbing materials which is cheaper and user friendly. Thus, in this research, the sound absorbent properties of bio-polymer foam filled with hybrid fillers of wood dust and waste tire rubber has been investigated. Waste cooking oil from crisp industries was converted into bio-monomer, filled with different proportion ratio of fillers and fabricated into bio-polymer foam composite. Two fabrication methods is applied which is the Close Mold Method (CMM) and Open Mold Method (OMM). A total of four bio-polymer foam composite samples were produce for each method used. The percentage of hybrid fillers; mixture of wood dust and waste tire rubber of 2.5 %, 5.0%, 7.5% and 10% weight to weight ration with bio-monomer. The sound absorption of the bio-polymer foam composites samples were tested by using the impedance tube test according to the ASTM E-1050 and Scanning Electron Microscope to determine the morphology and porosity of the samples. The sound absorption coefficient (α) at different frequency range revealed that the polymer foam of 10.0 % hybrid fillers shows highest α of 0.963. The highest hybrid filler loading contributing to smallest pore sizes but highest interconnected pores. This also revealed that when highly porous material is exposed to incident sound waves, the air molecules at the surface of the material and within the pores of the material are forced to vibrate and loses some of their original energy. This is concluded that the suitability of bio-polymer foam filled with hybrid fillers to be used in acoustic application of automotive components such as dashboards, door panels, cushion and etc.

  12. Numerical analyses of the sound absorption of cylindrical microperforated panel space absorbers with cores.

    Science.gov (United States)

    Toyoda, Masahiro; Fujita, Shota; Sakagami, Kimihiro

    2015-12-01

    Microperforated panels (MPPs) are next-generation absorption materials because they can provide wideband sound absorption without fibrous materials and can be composed of diverse materials to meet global environmental demands. The fundamental absorbing mechanism is Helmholtz-resonance absorption due to perforations and an air cavity. MPPs are typically backed by rigid flat walls, but to reduce the restrictions on the MPP absorber properties, one of the authors has proposed MPP space sound absorbers without backing structures, including three-dimensional cylindrical microperforated panel space absorbers (CMSAs). Advantages of MPPs without backing structures are design flexibility and ease of use. Besides, the absorption characteristics of a CMSA with a core, which has a rigid cylindrical core inside the CMSA, have been experimentally tested, but a method to predict the absorption characteristics is necessary to design CMSAs with cores. Herein the two-dimensional combined Helmholtz integral formulation method is employed, and its prediction accuracy is evaluated by comparing the measured and predicted absorption characteristics of a CMSA with a core. Furthermore, a parametric study with regard to the core size is carried out to investigate the transition of the absorbing mechanism.

  13. Study of physical and sound absorbing property of epoxy blended coir dust biocomposite

    Science.gov (United States)

    Nath, G.; Mishra, S. P.

    2016-09-01

    Reinforcement biocomposite has gained more attention recently due to its low cost, abundantly availability, low density, specific properties, easy method of separation, enhanced energy recovery, CO2 neutrality, biodegradability and recyclable in nature. As a waste product of coconut fruit, the coconut coir dust (CCD) obtained from the coconut husk. The biocomposite material prepared from the CCD modified with the proper blended solution with the help of ultrasonic technique. The study of adiabatic compressibility of acetone / water (70/30) worth its blending property for bleaching of CCD. The biocomposite material of CCD was prepared with epoxy resin. The different physical properties such as sound absorption coefficient, thermal conductivity and electrical conductivity were measured. The morphological study of biocomposite and measurement of sound absorption coefficient shows good evidence of sound absorbing characteristics of biocomposite of CCD. The sound absorption property of composite material shows a significant result where as the thermal conductivity and electrical conductivity executes a weak result. Thus biocomposite of CCD can acts as a good sound absorber and band conductor of heat and electric current.

  14. Predicted sound absorption coefficients of absorber materials lined in a chamber

    Directory of Open Access Journals (Sweden)

    Farhad Forouharmajd

    2014-01-01

    Full Text Available Aims: The present study was aimed to measurement of sound absorption coefficient of mineral wool and determination of their absorption ability. Materials and Methods: Mineral wool was used to find noise absorption coefficient. Random and normal sound absorption coefficient values were predicted. Then, the measures of transmission loss calculated as an overall value, for applied absorbent material and bare sheet metal. Results: The measured values of noise with one octave band frequency demonstrated an attenuation of 5.5-7 dB for these frequencies. The absorption coefficients of materials showed that mineral wool had more normal sound coefficients than its random sound absorption coefficient values. Conclusion: It can be concluded that predicted normal sound absorption coefficients of used mineral wool materials were near to the areas of standard line. It seems that the amount or thickness of absorbent lining was a main reason of noise reduction in low band frequencies. Mineral wool has a higher density and can provide better acoustical and insulating results than fiberglass. Besides, mineral wool doesn′t lose its insulating value when wet and has an outstanding resistance to fire.

  15. Acoustic behavior of a fibrous bulk material. [Kevlar 29 sound absorber

    Science.gov (United States)

    Hersh, A. S.; Walker, B.

    1979-01-01

    A semiempirical model is presented describing the acoustic behavior of Kevlar 29, a bulk absorbing material. The model is based on an approximate solution to the one-dimensional equations representing conservation of fluctuating mass, momentum and energy. By treating the material as a momentum sink, theoretical expressions of the material complex propagation constants and characteristic impedance were derived in terms of a single constant. Evaluating the constant at a single frequency for a particular specimen, excellent agreement between prediction and measurement was achieved for a large range of sound frequencies and material porosities and thicknesses. Results show that Kevlar 29 absorbs sound efficiently even at low frequencies. This is explained in terms of a frequency dependent material phase speed.

  16. Study on The Effectiveness of Egg Tray and Coir Fibre as A Sound Absorber

    Directory of Open Access Journals (Sweden)

    Kaamin Masiri

    2018-01-01

    Full Text Available Sound or noise pollution has become one major issues to the community especially those who lived in the urban areas. It does affect the activity of human life. This excessive noise is mainly caused by machines, traffic, motor vehicles and also any unwanted sounds that coming from outside and even from the inside of the building. Such as a loud music. Therefore, the installation of sound absorption panel is one way to reduce the noise pollution inside a building. The selected material must be a porous and hollow in order to absorb high frequency sound. This study was conducted to evaluate the potential of egg tray and coir fibre as a sound absorption panel. The coir fibre has a good coefficient value which make it suitable as a sound absorption material and can replace the traditional material; syntactic and wooden material. The combination of pyramid shape of egg tray can provide a large surface for uniform sound reflection. This study was conducted by using a panel with size 1 m x 1 m with a thickness of 6 mm. This panel consist of egg tray layer, coir fibre layer and a fabric as a wrapping for the aesthetic value. Room reverberation test has been carried to find the loss of reverberation time (RT. Result shows that, a reverberation time reading is on low frequency, which is 125 Hz to 1600 Hz. Within these frequencies, this panel can shorten the reverberation time of 5.63s to 3.60s. Hence, from this study, it can be concluded that the selected materials have the potential as a good sound absorption panel. The comparison is made with the previous research that used egg tray and kapok as a sound absorption panel.

  17. Study on The Effectiveness of Egg Tray and Coir Fibre as A Sound Absorber

    Science.gov (United States)

    Kaamin, Masiri; Farah Atiqah Ahmad, Nor; Ngadiman, Norhayati; Kadir, Aslila Abdul; Razali, Siti Nooraiin Mohd; Mokhtar, Mardiha; Sahat, Suhaila

    2018-03-01

    Sound or noise pollution has become one major issues to the community especially those who lived in the urban areas. It does affect the activity of human life. This excessive noise is mainly caused by machines, traffic, motor vehicles and also any unwanted sounds that coming from outside and even from the inside of the building. Such as a loud music. Therefore, the installation of sound absorption panel is one way to reduce the noise pollution inside a building. The selected material must be a porous and hollow in order to absorb high frequency sound. This study was conducted to evaluate the potential of egg tray and coir fibre as a sound absorption panel. The coir fibre has a good coefficient value which make it suitable as a sound absorption material and can replace the traditional material; syntactic and wooden material. The combination of pyramid shape of egg tray can provide a large surface for uniform sound reflection. This study was conducted by using a panel with size 1 m x 1 m with a thickness of 6 mm. This panel consist of egg tray layer, coir fibre layer and a fabric as a wrapping for the aesthetic value. Room reverberation test has been carried to find the loss of reverberation time (RT). Result shows that, a reverberation time reading is on low frequency, which is 125 Hz to 1600 Hz. Within these frequencies, this panel can shorten the reverberation time of 5.63s to 3.60s. Hence, from this study, it can be concluded that the selected materials have the potential as a good sound absorption panel. The comparison is made with the previous research that used egg tray and kapok as a sound absorption panel.

  18. Thermo-active building systems and sound absorbers: Thermal comfort under real operation conditions

    DEFF Research Database (Denmark)

    Köhler, Benjamin; Rage, Nils; Chigot, Pierre

    2018-01-01

    Radiant systems are established today and have a high ecological potential in buildings while ensuring thermal comfort. Free-hanging sound absorbers are commonly used for room acoustic control, but can reduce the heat exchange when suspended under an active slab. The aim of this study is to evalu......Radiant systems are established today and have a high ecological potential in buildings while ensuring thermal comfort. Free-hanging sound absorbers are commonly used for room acoustic control, but can reduce the heat exchange when suspended under an active slab. The aim of this study...... is to evaluate the impact on thermal comfort of horizontal and vertical free-hanging porous sound absorbers placed in rooms of a building cooled by Thermo-Active Building System (TABS), under real operation conditions. A design comparing five different ceiling coverage ratios and two room types has been...... implemented during three measurement periods. A clear correlation between increase of ceiling coverage ratio and reduction of thermal comfort could not be derived systematically for each measurement period and room type, contrarily to what was expected from literature. In the first two monitoring periods...

  19. Three-dimensional reconstruction of a random fibrous medium: Geometry, transport, and sound absorbing properties.

    Science.gov (United States)

    Luu, Hoang Tuan; Perrot, Camille; Monchiet, Vincent; Panneton, Raymond

    2017-06-01

    The main purpose of this article is to present, within a unified framework, a technique based on numerical homogenization, to model the acoustical properties of real fibrous media from their geometrical characteristics and to compare numerical results with experimental data. The authors introduce a reconstruction procedure for a random fibrous medium and use it as a basis for the computation of its geometrical, transport, and sound absorbing properties. The previously ad hoc "fiber anisotropies" and "volume weighted average radii," used to describe the experimental data on microstructure, are here measured using scanning electron microscopy. The authors show that these parameters, in conjunction with the bulk porosity, contribute to a precise description of the acoustical characteristics of fibrous absorbents. They also lead to an accurate prediction of transport parameters which can be used to predict acoustical properties. The computed values of the permeability and frequency-dependent sound absorption coefficient are successfully compared with permeability and impedance-tube measurements. The authors' results indicate the important effect of fiber orientation on flow properties associated with the different physical properties of fibrous materials. A direct link is provided between three-dimensional microstructure and the sound absorbing properties of non-woven fibrous materials, without the need for any empirical formulae or fitting parameters.

  20. In situ measurements of the oblique incidence sound absorption coefficient for finite sized absorbers

    DEFF Research Database (Denmark)

    Ottink, Marco; Brunskog, Jonas; Jeong, Cheol-Ho

    2016-01-01

    for the finiteness of the absorber. A sound field model, which accounts for scattering from the finite absorber edges, assuming plane wave incidence is derived. A significant influence of the finiteness on the radiation impedance and the corresponding absorption coefficient is found. A finite surface method, which......Absorption coefficients are mostly measured in reverberation rooms or with impedance tubes. Since these methods are only suitable for measuring the random incidence and the normal incidence absorption coefficient, there exists an increasing need for absorption coefficient measurement of finite...... absorbers at oblique incidence in situ. Due to the edge diffraction effect, oblique incidence methods considering an infinite sample fail to measure the absorption coefficient at large incidence angles of finite samples. This paper aims for the development of a measurement method that accounts...

  1. Mechanic and Acoustic Properties of the Sound-Absorbing Material Made from Natural Fiber and Polyester

    Directory of Open Access Journals (Sweden)

    Limin Peng

    2015-01-01

    Full Text Available A sound-absorbing composite material made of wood fiber and polyester fiber was produced using polyester foam technology and wood-based composite technology. This study investigated the physical and mechanical properties and the effects of the airflow resistivity of the materials and the depth of the cavities behind on sound-absorbing performance of the composite material. The results showed that the composite of best physical and mechanical properties and sound absorption was made with a 150°C hot-pressing temperature, 10 min hot-press time, 3 : 1 the ratio of wood fiber to polyester fiber, foaming agent content of 8%, and the nominal density of 0.2 g/cm3; the composite material yielded superior sound absorption property with the airflow resistivity of 1.98 × 105 Pa·s/m2; the acoustic absorption peak moved to lower frequencies when length of the cavities was increased.

  2. Corn Husk Fiber-Polyester Composites as Sound Absorber: Nonacoustical and Acoustical Properties

    Directory of Open Access Journals (Sweden)

    Nasmi Herlina Sari

    2017-01-01

    Full Text Available This study investigates the acoustical and nonacoustical properties of composites using corn husk fiber (CHF and unsaturated polyester as the sound-absorbing materials. The influence of the volume fraction of CHF on acoustic performance was experimentally investigated. In addition, the nonacoustical properties, such as air-flow resistivity, porosity, and mechanical properties of composites have been analyzed. The results show that the sound absorptions at low frequencies are determined by the number of lumens in fiber, particularly the absorption coefficient, which increases the amount of fiber. For high-frequency sound, the absorption coefficient is determined by the arrangement of fibers in the composite. An absorption coefficient is close to zero when the fibers are arranged in a conventional pattern; however, when they are arranged in a random pattern, a high absorption coefficient can be obtained. The bond interface between the fiber and resin enhances its mechanical properties, which increases the longevity of the composite panel.

  3. Experimental and Numerical Study of the Effects of Acoustic Sound Absorbers on the Cooling Performance of Thermally Active Building Systems

    DEFF Research Database (Denmark)

    Domínguez, L. Marcos; Kazanci, Ongun Berk; Rage, Nils

    2017-01-01

    %, respectively. With vertical sound absorbers, the decrease in cooling performance was 8%, 12%, and 14% for the corresponding cases, respectively. The numerical model predicted closely the cooling performance reduction, air temperatures and ceiling surface temperatures in most cases, while there were differences......Free-hanging horizontal and vertical sound absorbers are commonly used in buildings for room acoustic control; however, when these sound absorbers are used in combination with Thermally Active Building Systems, they will decrease the cooling performance of Thermally Active Building Systems...... and this will affect the thermal indoor environment in that space. Therefore, it is crucial to be able to quantify and model these effects in the design phase. This study quantifies experimentally the effects of horizontal and vertical free-hanging sound absorbers on the cooling performance of Thermally Active...

  4. In situ measurements of the oblique incidence sound absorption coefficient for finite sized absorbers.

    Science.gov (United States)

    Ottink, Marco; Brunskog, Jonas; Jeong, Cheol-Ho; Fernandez-Grande, Efren; Trojgaard, Per; Tiana-Roig, Elisabet

    2016-01-01

    Absorption coefficients are mostly measured in reverberation rooms or with impedance tubes. Since these methods are only suitable for measuring the random incidence and the normal incidence absorption coefficient, there exists an increasing need for absorption coefficient measurement of finite absorbers at oblique incidence in situ. Due to the edge diffraction effect, oblique incidence methods considering an infinite sample fail to measure the absorption coefficient at large incidence angles of finite samples. This paper aims for the development of a measurement method that accounts for the finiteness of the absorber. A sound field model, which accounts for scattering from the finite absorber edges, assuming plane wave incidence is derived. A significant influence of the finiteness on the radiation impedance and the corresponding absorption coefficient is found. A finite surface method, which combines microphone array measurements over a finite sample with the sound field model in an inverse manner, is proposed. Besides, a temporal subtraction method, a microphone array method, impedance tube measurements, and an equivalent fluid model are used for validation. The finite surface method gives promising agreement with theory, especially at near grazing incidence. Thus, the finite surface method is proposed for further measurements at large incidence angles.

  5. Dual-frequency sound-absorbing metasurface based on visco-thermal effects with frequency dependence

    Science.gov (United States)

    Ryoo, H.; Jeon, W.

    2018-03-01

    We investigate theoretically an acoustic metasurface with a high absorption coefficient at two frequencies and design it from subwavelength structures. We propose the use of a two-dimensional periodic array of four Helmholtz resonators in two types to obtain a metasurface with nearly perfect sound absorption at given target frequencies via interactions between waves emanating from different resonators. By considering how fluid viscosity affects acoustic energy dissipation in the narrow necks of the Helmholtz resonators, we obtain effective complex-valued material properties that depend on frequency and on the geometrical parameters of the resonators. We furthermore derive the effective acoustic impedance of the metasurface from the effective material properties and calculate the absorption spectra from the theoretical model, which we compare with the spectra obtained from a finite-element simulation. As a practical application of the theoretical model, we derive empirical formulas for the geometrical parameters of a metasurface which would yield perfect absorption at a given frequency. While previous works on metasurfaces based on Helmholtz resonators aimed to absorb sound at single frequencies, we use optimization to design a metasurface composed of four different Helmholtz resonators to absorb sound at two distinct frequencies.

  6. Effect of sound-absorbing coatings on the disturbance evolution in a flow of a mixture of vibrationally excited gases

    Science.gov (United States)

    Reshetova, A. I.; Poplavskaya, T. V.; Kirilovskiy, S. V.; Tsyrulnikov, I. S.

    2017-10-01

    The flow around a solid plate and a plate with a sound-absorbing coating at a non-zero angle of attack in a hypersonic flow (M∞=8.44) of a mixture of vibrationally excited carbon dioxide and nitrogen is considered. Numerical simulations are performed by solving two-dimensional unsteady Navier-Stokes equations with a two-temperature model of relaxing flows. The vibrational energy as a function of time is defined by the Landau-Teller equation. A skeleton model, which is a set of square elements arranged in a staggered order, is used for simulating the porous coating made of foamed nickel with a porosity coefficient of 95%. The distance between the elements is equal to the pore diameter of the real sound-absorbing material. Data on the evolution of disturbances on the solid plate and on the plate with the sound-absorbing coating are presented for various angles of attack and CO2 concentrations in the mixture. The experimental and calculated data on pressure fluctuations on the plate surfaces are found to be in good agreement. The effects of various parameters of the sound-absorbing coating (depth, length, and location at the flat plate) are considered. It is shown that the sound-absorbing coating significantly reduces the intensity of pressure fluctuations on the plate surface as compared to the solid surface (up to 50% depending on the length and location of the sound-absorbing coating).

  7. Microstructure representations for sound absorbing fibrous media: 3D and 2D multiscale modelling and experiments

    Science.gov (United States)

    Zieliński, Tomasz G.

    2017-11-01

    The paper proposes and investigates computationally-efficient microstructure representations for sound absorbing fibrous media. Three-dimensional volume elements involving non-trivial periodic arrangements of straight fibres are examined as well as simple two-dimensional cells. It has been found that a simple 2D quasi-representative cell can provide similar predictions as a volume element which is in general much more geometrically accurate for typical fibrous materials. The multiscale modelling allowed to determine the effective speeds and damping of acoustic waves propagating in such media, which brings up a discussion on the correlation between the speed, penetration range and attenuation of sound waves. Original experiments on manufactured copper-wire samples are presented and the microstructure-based calculations of acoustic absorption are compared with the corresponding experimental results. In fact, the comparison suggested the microstructure modifications leading to representations with non-uniformly distributed fibres.

  8. Measurement of the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field.

    Science.gov (United States)

    Robin, Olivier; Berry, Alain; Doutres, Olivier; Atalla, Noureddine

    2014-07-01

    This letter proposes an experimental method to estimate the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field in free-field conditions. Comparisons are made between experiments conducted with this approach, the standard reverberant room method, and numerical simulations using the transfer matrix method. With a simple experimental setup and smaller samples than those required by standards, the results obtained with the proposed approach do not exhibit non-physical trends of the reverberant room method and provide absorption coefficients in good agreement with those obtained by simulations for a laterally infinite material.

  9. Analysis of sound absorption performance of an electroacoustic absorber using a vented enclosure

    Science.gov (United States)

    Cho, Youngeun; Wang, Semyung; Hyun, Jaeyub; Oh, Seungjae; Goo, Seongyeol

    2018-03-01

    The sound absorption performance of an electroacoustic absorber (EA) is primarily influenced by the dynamic characteristics of the loudspeaker that acts as the actuator of the EA system. Therefore, the sound absorption performance of the EA is maximum at the resonance frequency of the loudspeaker and tends to degrade in the low-frequency and high-frequency bands based on this resonance frequency. In this study, to adjust the sound absorption performance of the EA system in the low-frequency band of approximately 20-80 Hz, an EA system using a vented enclosure that has previously been used to enhance the radiating sound pressure of a loudspeaker in the low-frequency band, is proposed. To verify the usefulness of the proposed system, two acoustic environments are considered. In the first acoustic environment, the vent of the vented enclosure is connected to an external sound field that is distinct from the sound field coupled to the EA. In this case, the acoustic effect of the vented enclosure on the performance of the EA is analyzed through an analytical approach using dynamic equations and an impedance-based equivalent circuit. Then, it is verified through numerical and experimental approaches. Next, in the second acoustic environment, the vent is connected to the same external sound field as the EA. In this case, the effect of the vented enclosure on the EA is investigated through an analytical approach and finally verified through a numerical approach. As a result, it is confirmed that the characteristics of the sound absorption performances of the proposed EA system using the vented enclosure in the two acoustic environments considered in this study are different from each other in the low-frequency band of approximately 20-80 Hz. Furthermore, several case studies on the change tendency of the performance of the EA using the vented enclosure according to the critical design factors or vent number for the vented enclosure are also investigated. In the future

  10. Dolphin Sounds-Inspired Covert Underwater Acoustic Communication and Micro-Modem

    Science.gov (United States)

    Qiao, Gang; Liu, Songzuo; Bilal, Muhammad

    2017-01-01

    A novel portable underwater acoustic modem is proposed in this paper for covert communication between divers or underwater unmanned vehicles (UUVs) and divers at a short distance. For the first time, real dolphin calls are used in the modem to realize biologically inspired Covert Underwater Acoustic Communication (CUAC). A variety of dolphin whistles and clicks stored in an SD card inside the modem helps to realize different biomimetic CUAC algorithms based on the specified covert scenario. In this paper, the information is conveyed during the time interval between dolphin clicks. TMS320C6748 and TLV320AIC3106 are the core processors used in our unique modem for fast digital processing and interconnection with other terminals or sensors. Simulation results show that the bit error rate (BER) of the CUAC algorithm is less than 10−5 when the signal to noise ratio is over ‒5 dB. The modem was tested in an underwater pool, and a data rate of 27.1 bits per second at a distance of 10 m was achieved. PMID:29068363

  11. Dolphin Sounds-Inspired Covert Underwater Acoustic Communication and Micro-Modem

    Directory of Open Access Journals (Sweden)

    Gang Qiao

    2017-10-01

    Full Text Available A novel portable underwater acoustic modem is proposed in this paper for covert communication between divers or underwater unmanned vehicles (UUVs and divers at a short distance. For the first time, real dolphin calls are used in the modem to realize biologically inspired Covert Underwater Acoustic Communication (CUAC. A variety of dolphin whistles and clicks stored in an SD card inside the modem helps to realize different biomimetic CUAC algorithms based on the specified covert scenario. In this paper, the information is conveyed during the time interval between dolphin clicks. TMS320C6748 and TLV320AIC3106 are the core processors used in our unique modem for fast digital processing and interconnection with other terminals or sensors. Simulation results show that the bit error rate (BER of the CUAC algorithm is less than 10 − 5 when the signal to noise ratio is over ‒5 dB. The modem was tested in an underwater pool, and a data rate of 27.1 bits per second at a distance of 10 m was achieved.

  12. Dolphin Sounds-Inspired Covert Underwater Acoustic Communication and Micro-Modem.

    Science.gov (United States)

    Qiao, Gang; Zhao, Yunjiang; Liu, Songzuo; Bilal, Muhammad

    2017-10-25

    A novel portable underwater acoustic modem is proposed in this paper for covert communication between divers or underwater unmanned vehicles (UUVs) and divers at a short distance. For the first time, real dolphin calls are used in the modem to realize biologically inspired Covert Underwater Acoustic Communication (CUAC). A variety of dolphin whistles and clicks stored in an SD card inside the modem helps to realize different biomimetic CUAC algorithms based on the specified covert scenario. In this paper, the information is conveyed during the time interval between dolphin clicks. TMS320C6748 and TLV320AIC3106 are the core processors used in our unique modem for fast digital processing and interconnection with other terminals or sensors. Simulation results show that the bit error rate (BER) of the CUAC algorithm is less than 10 - 5 when the signal to noise ratio is over ‒5 dB. The modem was tested in an underwater pool, and a data rate of 27.1 bits per second at a distance of 10 m was achieved.

  13. Characterization of Underwater Sounds Produced by a Backhoe Dredge Excavating Rock and Gravel

    Science.gov (United States)

    2012-12-01

    source levels of the 2,700-m3 hopper dredge The City of Westminster operating on the Hastings Shingle and calculated the broadband source level to 186...Assessment of underwater noise from dredging operations on the Hasting Shingle Bank. Report No. Subacoustech 758R0137. Popper, A. N. 2003. Effects of

  14. Attenuation of low-frequency underwater sound using an array of air-filled balloons and comparison to effective medium theory.

    Science.gov (United States)

    Lee, Kevin M; Wilson, Preston S; Wochner, Mark S

    2017-12-01

    The ultimate goal of this work is to accurately predict the attenuation through a collection of large (on the order of 10-cm-radius) tethered encapsulated bubbles used in underwater noise abatement systems. Measurements of underwater sound attenuation were performed during a set of lake experiments, where a low-frequency compact electromechanical sound source was surrounded by different arrays of encapsulated bubbles with various individual bubbles sizes and void fractions. The measurements were compared with an existing predictive model [Church, J. Acoust. Soc. Am. 97, 1510-1521 (1995)] of the dispersion relation for linear propagation in liquid containing encapsulated bubbles. Although the model was originally intended to describe ultrasound contrast agents, it is evaluated here for large bubbles, and hence low frequencies, as a design tool for future underwater noise abatement systems, and there is good quantitative agreement between the observations and the model.

  15. A Simulation Study on the Performance of Radiant Ceilings Combined with Free-Hanging Horizontal Sound Absorbers

    DEFF Research Database (Denmark)

    Kazanci, Ongun Berk; Domínguez, L. Marcos; Rage, Niels

    2018-01-01

    Radiant heating and cooling systems, and Thermally Active Building Systems (TABS) in particular, have several advantages such as benefiting from the low temperature heating and high temperature cooling principle, coupling with renewable energy sources, peak shifting and peak load reductions. When...... using TABS, most building simulation models assume an uncovered ceiling; however, this might not be the case in practice, due to the use of free-hanging horizontal (or vertical) sound absorbers for the control of room acoustic conditions. The use of sound absorbers will decrease the performance...... simulation software with a recently developed plug-in that allows simulating the effects of horizontal sound absorbers on the performance of TABS and on the thermal indoor environment. The change in thermal indoor environment and in performance of TABS were quantified, and the simulation results were...

  16. Numerical simulation of the effects of hanging sound absorbers on TABS cooling performance

    DEFF Research Database (Denmark)

    Rage, Nils; Kazanci, Ongun Berk; Olesen, Bjarne W.

    2016-01-01

    Recently there has been a considerable increase in the use of Thermally-Active Building Systems (TABS) in Europe as an energy-efficient and economical cooling and heating solution for buildings. However, this widespread solution requires large uncovered hard surfaces indoors, which can lead...... to a degradation of the room acoustic comfort. Therefore, challenges arise when this system has to be combined with acoustic requirements. Soffit-hanging sound absorbers embody a promising solution. This study focuses on quantifying their impact on the cooling performance of TABS, assessed by means of the cooling.......4% with a coverage of 80%. The presence of acoustic panels also affects the thermal comfort: the operative temperature in the room increases by 0.9°C in the former case and up to 1.6°C in the latter. Results also show that comfort ventilation supplied to the enclosure has a considerable influence on the thermal...

  17. Effects of Free-Hanging Horizontal Sound Absorbers on the Cooling Performance of Thermally Activated Building Systems

    DEFF Research Database (Denmark)

    Lacarte, Luis Marcos Domínguez; Rage, Nils; Kazanci, Ongun Berk

    2017-01-01

    with the performance of TABS and the occupant’s thermal comfort, but an appropriate acoustic design is needed to find the most suitable solution for each case. The results show a reduction of 11% of the cooling performance of the TABS when 43% of the ceiling area is covered with free-hanging horizontal sound absorbers...... the TABS and the room are desirable. In this study, the effects of free-hanging units on the cooling performance of TABS and the occupants’ thermal comfort was measured in a full-scale TABS laboratory. Investigations demonstrate that the use of freehanging sound absorbers are compatible...

  18. Acoustic characterization of a nonlinear vibroacoustic absorber at low frequencies and high sound levels

    Science.gov (United States)

    Chauvin, A.; Monteil, M.; Bellizzi, S.; Côte, R.; Herzog, Ph.; Pachebat, M.

    2018-03-01

    A nonlinear vibroacoustic absorber (Nonlinear Energy Sink: NES), involving a clamped thin membrane made in Latex, is assessed in the acoustic domain. This NES is here considered as an one-port acoustic system, analyzed at low frequencies and for increasing excitation levels. This dynamic and frequency range requires a suitable experimental technique, which is presented first. It involves a specific impedance tube able to deal with samples of sufficient size, and reaching high sound levels with a guaranteed linear response thank's to a specific acoustic source. The identification method presented here requires a single pressure measurement, and is calibrated from a set of known acoustic loads. The NES reflection coefficient is then estimated at increasing source levels, showing its strong level dependency. This is presented as a mean to understand energy dissipation. The results of the experimental tests are first compared to a nonlinear viscoelastic model of the membrane absorber. In a second step, a family of one degree of freedom models, treated as equivalent Helmholtz resonators is identified from the measurements, allowing a parametric description of the NES behavior over a wide range of levels.

  19. First- and Second-level Bayesian Inference of Flow Resistivity of Sound Absorber and Room’s Influence

    DEFF Research Database (Denmark)

    Choi, Sang-Hyeon; Lee, Ikjin; Jeong, Cheol-Ho

    2016-01-01

    Sabine absorption coefficient is a widely used one deduced from reverberation time measurements via the Sabine equation. First- and second-level Bayesian analysis are used to estimate the flow resistivity of a sound absorber and the influences of the test chambers from Sabine absorption...

  20. The noisy underwater world : the effect of sound on behaviour of captive zebrafish

    NARCIS (Netherlands)

    Shafiei Sabet, Saeed

    2016-01-01

    Over the past few decades, public attention, activities in the field of conservation and animal welfare by nongovernmental organizations (NGOs), and scientific exploration are raising awareness on the potential effects of sounds on marine mammals and fish species. The aim of this thesis was to

  1. [The potential of tone audiometry for the determination of the sound-absorbing properties of various materials].

    Science.gov (United States)

    Zinkin, V N; Sheshegov, P M

    2014-01-01

    The objective of the present work was to experimentally estimate the potential of the tone audiometry technique for the determination of the sound-absorbing properties of various material. The study included 15 subjects at the age from 19 to 32 years. Their audiological examination was followed by the placement of the 5×7 cm spacer plate from the study material beneath the bone vibrator telephone to determine the bone sound-conduction threshold; no air-marking was undertaken. The sound absorption by the study materials of interest was determined in each octave-band from 250 to 8000 Hz from the difference between the starting audiogram and the audiogram of the material of interest. The study was carried out in three stages: (1) evaluation of sound absorption of each of the five materials, (2) measurement of the same parameter in the combinations of 2--4 layers for increasing sound absorption, and (3) fixation of the bone conduction telephone by the operator's hand (the head-mounted harness was used for the same purpose at stages 1 and 2). The experiments demonstrated that the study of bone sound conduction by means of tone audiometry allows to estimate the sound absorption of various materials. This technique may be applied for the development of a subjective method for the measurement of sound absorption in order to evaluate the acoustic effectiveness of materials that can be used to construct individual protective anti-noise devices.

  2. Rice straw-wood particle composite for sound absorbing wooden construction materials.

    Science.gov (United States)

    Yang, Han-Seung; Kim, Dae-Jun; Kim, Hyun-Joong

    2003-01-01

    In this study, rice straw-wood particle composite boards were manufactured as insulation boards using the method used in the wood-based panel industry. The raw material, rice straw, was chosen because of its availability. The manufacturing parameters were: a specific gravity of 0.4, 0.6, and 0.8, and a rice straw content (10/90, 20/80, and 30/70 weight of rice straw/wood particle) of 10, 20, and 30 wt.%. A commercial urea-formaldehyde adhesive was used as the composite binder, to achieve 140-290 psi of bending modulus of rupture (MOR) with 0.4 specific gravity, 700-900 psi of bending MOR with 0.6 specific gravity, and 1400-2900 psi of bending MOR with a 0.8 specific gravity. All of the composite boards were superior to insulation board in strength. Width and length of the rice straw particle did not affect the bending MOR. The composite boards made from a random cutting of rice straw and wood particles were the best and recommended for manufacturing processes. Sound absorption coefficients of the 0.4 and 0.6 specific gravity boards were higher than the other wood-based materials. The recommended properties of the rice straw-wood particle composite boards are described, to absorb noises, preserve the temperature of indoor living spaces, and to be able to partially or completely substitute for wood particleboard and insulation board in wooden constructions.

  3. Factors affecting sound energy absorbance in acute otitis media model of chinchilla.

    Science.gov (United States)

    Guan, Xiying; Seale, Thomas W; Gan, Rong Z

    2017-07-01

    Acute otitis media (AOM) is a rapid-onset infection of the middle ear which results in middle ear pressure (MEP), middle ear effusion (MEE), and structural changes in middle ear tissues. Previous studies from our laboratory have identified that MEP, MEE, and middle ear structural changes are three factors affecting tympanic membrane (TM) mobility and hearing levels (Guan et al., 2014, 2013). Sound energy reflectance or absorbance (EA) is a diagnostic tool increasingly used in clinical settings for the identification of middle ear diseases. However, it is unclear whether EA can differentiate these three factors in an AOM ear. Here we report wideband EA measurements in the AOM model of chinchilla at three experimental stages: unopened, pressure released, and effusion removed. These correspond to the combined and individual effects of the three factors on sound energy transmission. AOM was produced by transbullar injection of Haemophilus influenzae in two treatment groups: 4 days (4D) and 8 days (8D) post inoculation. These time points represent the relatively early and later phase of AOM. In each group of chinchillas, EA at 250-8000 Hz was measured using a wideband tympanometer at three experimental stages. Results show that the effects of MEP, MEE, and tissue structural changes over the frequency range varied with the disease time course. MEP was the primary contributor to reduction of EA in 4D AOM ears and had a smaller effect in 8D ears. MEE reduced the EA at 6-8 kHz in 4D ears and 2-8 kHz in 8D ears and was responsible for the EA peak in both 4D and 8D ears. The residual EA loss due to structural changes was observed over the frequency range in 8D ears and only at high frequencies in 4D ears. The EA measurements were also compared with the published TM mobility loss in chinchilla AOM ears. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Manufacturing Sound Absorber Based on Combined Recycling of Polyethylene Trephetalat and Polystyrene at Low and Median Frequencies

    Directory of Open Access Journals (Sweden)

    Zeynolabedin Ghanbarzadeh Alamdari

    2008-06-01

    Full Text Available Background and aim: Noise pollution is one of the main cause of occupational hearing loss. According to WHO reports in many countries workers have been exposed to 85 – 90 dB noise level. The purpose of this study is to manufacture a sound absorber based on combined recycled polyethylene trephetalat (PET and polystyrene (PS with an economical method in order to control of noise Pollution Materials and methods: Sound absorber were made of PET and PS with equal weight percent, polyester fiber, and polyvinyl acetate resine, with five to ten centimeters thick. Sound mean absorption coefficient percents were determined by acoustic impedance tube and compared with those of rock wool. Results: Mean absorption coefficient percent of samples with one to five millimeter pore size and ten centimeters thickness was significantly better than those with six to twenty millimeters pore size in 50 to 630, 1250, and 1600 Hz, (p<0.05. In general, samples mean absorption coehicient was significally different from those rock wool (p=0.005.Conclusion: Recycle polymere absorbers may play an important role in national economics as they are prophylactic to some occupational disease and also are economical.

  5. Novel recycling of nonmetal particles from waste printed wiring boards to produce porous composite for sound absorbing application.

    Science.gov (United States)

    Sun, Zhixing; Shen, Zhigang; Zhang, Xiaojing; Ma, Shulin

    2014-01-01

    Nonmetal materials take up about 70 wt% of waste printed wiring boards (WPWB), which are usually recycled as low-value fillers or even directly disposed by landfill dumping and incineration. In this research, a novel reuse ofthe nonmetals to produce porous composites for sound absorbing application was demonstrated. The manufacturing process, absorbing performance and mechanical properties of the composites were studied. The results show that the high porous structure of the composites leads to an excellent sound absorption ability in broad-band frequency range. Average absorption coefficient of above 0.4 can be achievedby the composite in the frequency range from 100 to 6400 Hz. When the particle size is larger than 0.2 mm, the absorption ability of the composite is comparable to that of commercial wood-fibre board and urea-formaldehyde foam. Mechanical analysis indicates that the porous composites possess sufficient structural strength for self-sustaining applications. All the results indicate that producing sound absorbing composite with nonmetal particles from WPWB provides an efficient and profitable way for recycling this waste resource and can resolve both the environment pollution and noise pollution problems.

  6. Acoustic inversion with self noise of an autonomous underwater vehicle to measure sound speed in marine sediments

    NARCIS (Netherlands)

    van Leijen, A.V.; Rothkranz, L.J.M.; Groen, F.C.A.

    2009-01-01

    This work reports on an experiment from the Maritime Rapid Environmental Assessment sea trials in 2007, where autonomous underwater vehicles were deployed for environmental assessment. Even though these underwater vehicles are very quiet platforms, this work investigates the potential of vehicle

  7. Sound Control in the Physic Lab in the Polyacryl Company and Studying the Noise Reduction by Means of Different Absorbents

    Directory of Open Access Journals (Sweden)

    Harandi

    1999-03-01

    Full Text Available Studying noise effect at the workplace has more various aspects than other factors. So it is not surprising that its adverse impact on the physical and mental state of the society has been detected to some extent. There is a significant correlation between the hearing loss and the noise pollution of the workplaces. The most important ways to lessen and control the impact of noise are: substituting the noisy equipments with ones that produce less noise, correcting noise sources and isolating the sound source. In the current study we tried to control the noise level by using various sound absorbents and measured sound level by using these different substances. The results of these measurements have reported in the current article in details.

  8. A statistical method for predicting sound absorbing property of porous metal materials by using quartet structure generation set

    International Nuclear Information System (INIS)

    Guan, Dong; Wu, Jiu Hui; Jing, Li

    2015-01-01

    Highlights: • A random internal morphology and structure generation-growth method, termed as the quartet structure generation set (QSGS), has been utilized based on the stochastic cluster growth theory for numerical generating the various microstructures of porous metal materials. • Effects of different parameters such as thickness and porosity on sound absorption performance of the generated structures are studied by the present method, and the obtained results are validated by an empirical model as well. • This method could be utilized to guide the design and fabrication of the sound-absorption porous metal materials. - Abstract: In this paper, a statistical method for predicting sound absorption properties of porous metal materials is presented. To reflect the stochastic distribution characteristics of the porous metal materials, a random internal morphology and structure generation-growth method, termed as the quartet structure generation set (QSGS), has been utilized based on the stochastic cluster growth theory for numerical generating the various microstructures of porous metal materials. Then by using the transfer-function approach along with the QSGS tool, we investigate the sound absorbing performance of porous metal materials with complex stochastic geometries. The statistical method has been validated by the good agreement among the numerical results for metal rubber from this method and a previous empirical model and the corresponding experimental data. Furthermore, the effects of different parameters such as thickness and porosity on sound absorption performance of the generated structures are studied by the present method, and the obtained results are validated by an empirical model as well. Therefore, the present method is a reliable and robust method for predicting the sound absorption performance of porous metal materials, and could be utilized to guide the design and fabrication of the sound-absorption porous metal materials

  9. Bottom-up approach for microstructure optimization of sound absorbing materials.

    Science.gov (United States)

    Perrot, Camille; Chevillotte, Fabien; Panneton, Raymond

    2008-08-01

    Results from a numerical study examining micro-/macrorelations linking local geometry parameters to sound absorption properties are presented. For a hexagonal structure of solid fibers, the porosity phi, the thermal characteristic length Lambda('), the static viscous permeability k(0), the tortuosity alpha(infinity), the viscous characteristic length Lambda, and the sound absorption coefficient are computed. Numerical solutions of the steady Stokes and electrical equations are employed to provide k(0), alpha(infinity), and Lambda. Hybrid estimates based on direct numerical evaluation of phi, Lambda('), k(0), alpha(infinity), Lambda, and the analytical model derived by Johnson, Allard, and Champoux are used to relate varying (i) throat size, (ii) pore size, and (iii) fibers' cross-section shapes to the sound absorption spectrum. The result of this paper tends to demonstrate the important effect of throat size in the sound absorption level, cell size in the sound absorption frequency selectivity, and fibers' cross-section shape in the porous material weight reduction. In a hexagonal porous structure with solid fibers, the sound absorption level will tend to be maximized with a 48+/-10 microm throat size corresponding to an intermediate resistivity, a 13+/-8 microm fiber radius associated with relatively small interfiber distances, and convex triangular cross-section shape fibers allowing weight reduction.

  10. Acoustic contributions of a sound absorbing blanket placed in a double panel structure: absorption versus transmission.

    Science.gov (United States)

    Doutres, Olivier; Atalla, Noureddine

    2010-08-01

    The objective of this paper is to propose a simple tool to estimate the absorption vs. transmission loss contributions of a multilayered blanket unbounded in a double panel structure and thus guide its optimization. The normal incidence airborne sound transmission loss of the double panel structure, without structure-borne connections, is written in terms of three main contributions; (i) sound transmission loss of the panels, (ii) sound transmission loss of the blanket and (iii) sound absorption due to multiple reflections inside the cavity. The method is applied to four different blankets frequently used in automotive and aeronautic applications: a non-symmetric multilayer made of a screen in sandwich between two porous layers and three symmetric porous layers having different pore geometries. It is shown that the absorption behavior of the blanket controls the acoustic behavior of the treatment at low and medium frequencies and its transmission loss at high frequencies. Acoustic treatment having poor sound absorption behavior can affect the performance of the double panel structure.

  11. Rainbow-trapping absorbers: Broadband, perfect and asymmetric sound absorption by subwavelength panels for transmission problems.

    Science.gov (United States)

    Jiménez, Noé; Romero-García, Vicent; Pagneux, Vincent; Groby, Jean-Philippe

    2017-10-19

    Perfect, broadband and asymmetric sound absorption is theoretically, numerically and experimentally reported by using subwavelength thickness panels in a transmission problem. The panels are composed of a periodic array of varying crosssection waveguides, each of them being loaded by Helmholtz resonators (HRs) with graded dimensions. The low cut-off frequency of the absorption band is fixed by the resonance frequency of the deepest HR, that reduces drastically the transmission. The preceding HR is designed with a slightly higher resonance frequency with a geometry that allows the impedance matching to the surrounding medium. Therefore, reflection vanishes and the structure is critically coupled. This results in perfect sound absorption at a single frequency. We report perfect absorption at 300 Hz for a structure whose thickness is 40 times smaller than the wavelength. Moreover, this process is repeated by adding HRs to the waveguide, each of them with a higher resonance frequency than the preceding one. Using this frequency cascade effect, we report quasi-perfect sound absorption over almost two frequency octaves ranging from 300 to 1000 Hz for a panel composed of 9 resonators with a total thickness of 11 cm, i.e., 10 times smaller than the wavelength at 300 Hz.

  12. Diel and seasonal patterns of underwater sounds by Weddell seals, leopard seals, and killer whales in the Antarctic: When it's adaptive to be quiet

    Science.gov (United States)

    Mindach, Debrah; Thomas, Jeanette

    2005-09-01

    Automated underwater recordings taken during the austral breeding season of the Weddell seal (Leptonychotes weddellii) in Antarctica also provided data on the vocalizations of predators in the area; leopard seals (Hydrurga leptonyx) and killer whales (Orcinus orca). Weddell seals inhabit fast ice areas to give birth, mate, and molt. Near the end of the breeding season in December the fast ice often breaks out and the two pack ice predators are able to move near the Weddell seal colonies and prey on them, especially pups. Recordings were taken continuously for a 2.5-min period each hour from mid-October 1977 and late-January 1978 at Hutton Cliffs and South Turtle Rock Crack, in McMurdo Sound. The leopard seals increased their trill calls when killer whales came into the area as evidenced by an increase in their frequency-modulated squeak calls. Weddell seals decreased their vocalization rate dramatically (~10 sounds/min) compared to during the peak of the breeding season (~75 sounds/min). Perhaps by being quiet, Weddell seals do not attract predators to their area.

  13. Carbon Nanotube Underwater Acoustic Thermophone

    Science.gov (United States)

    2016-09-23

    Attorney Docket No. 300009 1 of 8 A CARBON NANOTUBE UNDERWATER ACOUSTIC THERMOPHONE STATEMENT OF GOVERNMENT INTEREST [0001] The...the Invention [0003] The present invention is an acoustically transparent carbon nanotube thermophone. (2) Description of the Prior Art [0004...amplitude of the resulting sound waves. [0006] Recently, there has been development of underwater acoustic carbon nanotube (CNT) yarn sheets capable

  14. Transfer matrix method applied to the parallel assembly of sound absorbing materials.

    Science.gov (United States)

    Verdière, Kévin; Panneton, Raymond; Elkoun, Saïd; Dupont, Thomas; Leclaire, Philippe

    2013-12-01

    The transfer matrix method (TMM) is used conventionally to predict the acoustic properties of laterally infinite homogeneous layers assembled in series to form a multilayer. In this work, a parallel assembly process of transfer matrices is used to model heterogeneous materials such as patchworks, acoustic mosaics, or a collection of acoustic elements in parallel. In this method, it is assumed that each parallel element can be modeled by a 2 × 2 transfer matrix, and no diffusion exists between elements. The resulting transfer matrix of the parallel assembly is also a 2 × 2 matrix that can be assembled in series with the classical TMM. The method is validated by comparison with finite element (FE) simulations and acoustical tube measurements on different parallel/series configurations at normal and oblique incidence. The comparisons are in terms of sound absorption coefficient and transmission loss on experimental and simulated data and published data, notably published data on a parallel array of resonators. From these comparisons, the limitations of the method are discussed. Finally, applications to three-dimensional geometries are studied, where the geometries are discretized as in a FE concept. Compared to FE simulations, the extended TMM yields similar results with a trivial computation time.

  15. Whose Line Sound is it Anyway? Identifying the Vocalizer on Underwater Video by Localizing with a Hydrophone Array

    Directory of Open Access Journals (Sweden)

    Matthias Hoffmann-Kuhnt

    2016-11-01

    Full Text Available A new device that combined high-resolution (1080p wide-angle video and three channels of high-frequency acoustic recordings (at 500 kHz per channel in a portable underwater housing was designed and tested with wild bottlenose and spotted dolphins in the Bahamas. It consisted of three hydrophones, a GoPro camera, a small Fit PC, a set of custom preamplifiers and a high-frequency data acquisition board. Recordings were obtained to identify individual vocalizing animals through time-delay-of-arrival localizing in post-processing. The calculated source positions were then overlaid onto the video – providing the ability to identify the vocalizing animal on the recorded video. The new tool allowed for much clearer analysis of the acoustic behavior of cetaceans than was possible before.

  16. The Use of Sound Absorbing Shading Systems for the Attenuation of Noise on Building Façades. An Experimental Investigation

    Directory of Open Access Journals (Sweden)

    Nicolò Zuccherini Martello

    2015-12-01

    Full Text Available The problem of solar irradiation in building façades with large windows is often solved with the use of external shading devices, such as brise-soleil systems, but their potential acoustic effects on building façades are usually neglected. The purpose of this work is a preliminary consideration of the acoustic behaviour of brise-soleil systems and, furthermore, the evaluation of the possibility to improve their performances, in terms of Sound Pressure Level (SPL abatement over glass surfaces. The paper reports the results of a study on two portions of the same office building, with shading devices installed in front of large windows. Both airborne sound insulation measurements and SPL measurements over the glass surfaces of the windows were carried out to compare different situations, with or without louvers, and with sound absorbing experimental louvers as well. Results show that the louvers' presence can produce an increase in the SPL over the glass surface as a consequence of the reflection of the sound. Results further show that sound absorbing louvers improve the noise protection of the system, in terms of the SPL reduction, over glass surfaces, cancelling out the negative effect of the standard shading devices.

  17. Seabed sediment classification for monitoring underwater nourishments using time series of multi-beam echo-soundings

    Science.gov (United States)

    Gaida, T. C.; Snellen, M.; van Dijk, T. A. G. P.; Simons, D. G.

    2017-12-01

    Coastal erosion induced by natural processes, such as wind, waves, tidal currents, or human interferences endangers human beings, infrastructure, fauna and flora at the oceans and rivers all over the world. In The Netherlands, in particular the North Sea islands are strongly affected by sediment erosion. To protect and stabilize the coastline, beach and shoreface nourishments are frequently performed. Thereby, sediment reservoirs are created that replace the eroded sediments. Increasing the long-term efficiency of coastal protection requires monitoring of the temporal and spatial development of the coastal nourishments. Multi-beam echo-sounders (MBES) allow for detailed and comprehensive investigations of the seabed composition and structure. To investigate the potential of using MBES for monitoring nourishments in a tidal inlet, four MBES surveys per year are carried out at the Dutch Wadden island Ameland. A pre-nourishment MBES survey was performed in April 2017 and the subsequent post-nourishment survey will take place in September 2017. Both surveys are equipped with a Kongsberg EM 2040C dual-head MBES and are supported with extensive grab sampling. In this study the use of MBES backscatter and bathymetry data are considered as an approach for monitoring coastal nourishments. The aim is to develop a monitoring procedure that allows for comparing MBES data taken during different surveys, i.e., with variations in environmental conditions, MBES characteristics and acquisition procedures. Different unsupervised and supervised acoustic seafloor classification techniques are applied to the processed MBES data to classify the seabed sediments. The analysis of the pre-nourishment MBES data indicates that the backscatter and consequently the classification are highly driven by the abundancy of shell fragments. These results will be used as a baseline to investigate the accumulation of the underwater nourishments. Independent grab samples will be used to select the

  18. Observations of shallow water marine ambient sound: the low frequency underwater soundscape of the central Oregon coast.

    Science.gov (United States)

    Haxel, Joseph H; Dziak, Robert P; Matsumoto, Haru

    2013-05-01

    A year-long experiment (March 2010 to April 2011) measuring ambient sound at a shallow water site (50 m) on the central OR coast near the Port of Newport provides important baseline information for comparisons with future measurements associated with resource development along the inner continental shelf of the Pacific Northwest. Ambient levels in frequencies affected by surf-generated noise (f whale vocalizations. Additionally, an increase in spectral levels for frequencies ranging from 35 to 100 Hz is attributed to noise radiated from distant commercial ship commerce. One-second root mean square (rms) sound pressure level (SPLrms) estimates calculated across the 10-840 Hz frequency band for the entire year long deployment show minimum, mean, and maximum values of 84 dB, 101 dB, and 152 dB re 1 μPa.

  19. Sound

    CERN Document Server

    Robertson, William C

    2003-01-01

    Muddled about what makes music? Stuck on the study of harmonics? Dumbfounded by how sound gets around? Now you no longer have to struggle to teach concepts you really don t grasp yourself. Sound takes an intentionally light touch to help out all those adults science teachers, parents wanting to help with homework, home-schoolers seeking necessary scientific background to teach middle school physics with confidence. The book introduces sound waves and uses that model to explain sound-related occurrences. Starting with the basics of what causes sound and how it travels, you'll learn how musical instruments work, how sound waves add and subtract, how the human ear works, and even why you can sound like a Munchkin when you inhale helium. Sound is the fourth book in the award-winning Stop Faking It! Series, published by NSTA Press. Like the other popular volumes, it is written by irreverent educator Bill Robertson, who offers this Sound recommendation: One of the coolest activities is whacking a spinning metal rod...

  20. Sound

    CERN Document Server

    2013-01-01

    Sound has the power to soothe, excite, warn, protect, and inform. Indeed, the transmission and reception of audio signals pervade our daily lives. Readers will examine the mechanics and properties of sound and provides an overview of the "interdisciplinary science called acoustics." Also covered are functions and diseases of the human ear.

  1. Sound

    CERN Document Server

    Rivera, Andrea

    2017-01-01

    Sound is all around us. Learn how it is used in art, technology, and engineering. Five easy-to-read chapters explain the science behind sound, as well as its real-world applications. Vibrant, full-color photos, bolded glossary words, and a key stats section let readers zoom in even deeper. Aligned to Common Core Standards and correlated to state standards. Abdo Zoom is a division of ABDO.

  2. Underwater robots

    CERN Document Server

    Antonelli, Gianluca

    2014-01-01

    This book, now at the third edition, addresses the main control aspects in underwater manipulation tasks. The mathematical model with significant impact on the control strategy is discussed. The problem of controlling a 6-degrees-of-freedoms autonomous underwater vehicle is deeply investigated and a survey of fault detection/tolerant strategies for unmanned underwater vehicles is provided. Inverse kinematics, dynamic and interaction control for underwater vehicle-manipulator systems are then discussed. The code used to generate most of the numerical simulations is made available and briefly discussed.       

  3. Google™ underwater

    Science.gov (United States)

    Showstack, Randy

    2012-10-01

    The first underwater panoramic images were added to Google Maps™, the company announced on 25 September. This first “underwater Street View collection,” launched in partnership with the Caitlin Seaview Survey, provides people with the opportunity to “become the next virtual Jacques Cousteau.” For more information, see: maps.google.com/ocean.

  4. Underwater Vehicle

    National Research Council Canada - National Science Library

    Dick, James L

    2007-01-01

    There is thus provided an underwater vehicle having facility for maneuvering alongside a retrieving vehicle, as by manipulation of bow and stern planes, for engaging a hull surface of the retrieving...

  5. Ultrathin metasurface with high absorptance for waterborne sound

    KAUST Repository

    Mei, Jun

    2018-01-12

    We present a design for an acoustic metasurface which can efficiently absorb low-frequency sound energy in water. The metasurface has a simple structure and consists of only two common materials: i.e., water and silicone rubber. The optimized material and geometrical parameters of the designed metasurface are determined by an analytic formula in conjunction with an iterative process based on the retrieval method. Although the metasurface is as thin as 0.15 of the wavelength, it can absorb 99.7% of the normally incident sound wave energy. Furthermore, the metasurface maintains a substantially high absorptance over a relatively broad bandwidth, and also works well for oblique incidence with an incident angle of up to 50°. Potential applications in the field of underwater sound isolation are expected.

  6. Ultrathin metasurface with high absorptance for waterborne sound

    Science.gov (United States)

    Mei, Jun; Zhang, Xiujuan; Wu, Ying

    2018-03-01

    We present a design for an acoustic metasurface which can efficiently absorb low-frequency sound energy in water. The metasurface has a simple structure and consists of only two common materials: i.e., water and silicone rubber. The optimized material and geometrical parameters of the designed metasurface are determined by an analytic formula in conjunction with an iterative process based on the retrieval method. Although the metasurface is as thin as 0.15 of the wavelength, it can absorb 99.7% of the normally incident sound wave energy. Furthermore, the metasurface maintains a substantially high absorptance over a relatively broad bandwidth, and also works well for oblique incidence with an incident angle of up to 50°. Potential applications in the field of underwater sound isolation are expected.

  7. Underwater Noise from a Wave Energy Converter Is Unlikely to Affect Marine Mammals

    OpenAIRE

    Tougaard, Jakob

    2015-01-01

    Underwater noise was recorded from the Wavestar wave energy converter; a full-scale hydraulic point absorber, placed on a jack-up rig on the Danish North Sea coast. Noise was recorded 25 m from the converter with an autonomous recording unit (10 Hz to 20 kHz bandwidth). Median sound pressure levels (Leq) in third-octave bands during operation of the converter were 106-109 dB re. 1 μPa in the range 125-250 Hz, 1-2 dB above ambient noise levels (statistically significant). Outside the range 125...

  8. Propagation of sound

    DEFF Research Database (Denmark)

    Wahlberg, Magnus; Larsen, Ole Næsbye

    2017-01-01

    properties can be modified by sound absorption, refraction, and interference from multi paths caused by reflections.The path from the source to the receiver may be bent due to refraction. Besides geometrical attenuation, the ground effect and turbulence are the most important mechanisms to influence...... communication sounds for airborne acoustics and bottom and surface effects for underwater sounds. Refraction becomes very important close to shadow zones. For echolocation signals, geometric attenuation and sound absorption have the largest effects on the signals....

  9. Sound a very short introduction

    CERN Document Server

    Goldsmith, Mike

    2015-01-01

    Sound is integral to how we experience the world, in the form of noise as well as music. But what is sound? What is the physical basis of pitch and harmony? And how are sound waves exploited in musical instruments? Sound: A Very Short Introduction looks at the science of sound and the behaviour of sound waves with their different frequencies. It also explores sound in different contexts, covering the audible and inaudible, sound underground and underwater, acoustic and electronic sound, and hearing in humans and animals. It concludes with the problem of sound out of place—noise and its reduction.

  10. Underwater Hearing in Turtles.

    Science.gov (United States)

    Willis, Katie L

    2016-01-01

    The hearing of turtles is poorly understood compared with the other reptiles. Although the mechanism of transduction of sound into a neural signal via hair cells has been described in detail, the rest of the auditory system is largely a black box. What is known is that turtles have higher hearing thresholds than other reptiles, with best frequencies around 500 Hz. They also have lower underwater hearing thresholds than those in air, owing to resonance of the middle ear cavity. Further studies demonstrated that all families of turtles and tortoises share a common middle ear cavity morphology, with scaling best suited to underwater hearing. This supports an aquatic origin of the group. Because turtles hear best under water, it is important to examine their vulnerability to anthropogenic noise. However, the lack of basic data makes such experiments difficult because only a few species of turtles have published audiograms. There are also almost no behavioral data available (understandable due to training difficulties). Finally, few studies show what kinds of sounds are behaviorally relevant. One notable paper revealed that the Australian snake-necked turtle (Chelodina oblonga) has a vocal repertoire in air, at the interface, and under water. Findings like these suggest that there is more to the turtle aquatic auditory scene than previously thought.

  11. 4th Pacific Rim Underwater Acoustics Conference

    CERN Document Server

    Xu, Wen; Cheng, Qianliu; Zhao, Hangfang

    2016-01-01

    These proceedings are a collection of 16 selected scientific papers and reviews by distinguished international experts that were presented at the 4th Pacific Rim Underwater Acoustics Conference (PRUAC), held in Hangzhou, China in October 2013. The topics discussed at the conference include internal wave observation and prediction; environmental uncertainty and coupling to sound propagation; environmental noise and ocean dynamics; dynamic modeling in acoustic fields; acoustic tomography and ocean parameter estimation; time reversal and matched field processing; underwater acoustic localization and communication as well as measurement instrumentations and platforms. These proceedings provide insights into the latest developments in underwater acoustics, promoting the exchange of ideas for the benefit of future research.

  12. Underwater manipulator

    Science.gov (United States)

    Schrum, P.B.; Cohen, G.H.

    1993-04-20

    Self-contained, waterproof, water-submersible, remote-controlled apparatus is described for manipulating a device, such as an ultrasonic transducer for measuring crack propagation on an underwater specimen undergoing shock testing. The subject manipulator includes metal bellows for transmittal of angular motions without the use of rotating shaft seals or O-rings. Inside the manipulator, a first stepper motor controls angular movement. In the preferred embodiment, the bellows permit the first stepper motor to move an ultrasonic transducer [plus minus]45 degrees in a first plane and a second bellows permit a second stepper motor to move the transducer [plus minus]10 degrees in a second plane orthogonal to the first. In addition, an XY motor-driven table provides XY motion.

  13. Underwater manipulator

    International Nuclear Information System (INIS)

    Schrum, P.B.; Cohen, G.H.

    1993-01-01

    Self-contained, waterproof, water-submersible, remote-controlled apparatus is described for manipulating a device, such as an ultrasonic transducer for measuring crack propagation on an underwater specimen undergoing shock testing. The subject manipulator includes metal bellows for transmittal of angular motions without the use of rotating shaft seals or O-rings. Inside the manipulator, a first stepper motor controls angular movement. In the preferred embodiment, the bellows permit the first stepper motor to move an ultrasonic transducer ±45 degrees in a first plane and a second bellows permit a second stepper motor to move the transducer ±10 degrees in a second plane orthogonal to the first. In addition, an XY motor-driven table provides XY motion

  14. Specialization for underwater hearing by the tympanic middle ear of the turtle, Trachemys scripta elegans

    DEFF Research Database (Denmark)

    Christensen-Dalsgaard, J.; Brandt, Christian; Willis, K. L.

    2012-01-01

    Turtles, like other amphibious animals, face a trade-off between terrestrial and aquatic hearing. We used laser vibrometry and auditory brainstem responses to measure their sensitivity to vibration stimuli and to airborne versus underwater sound. Turtles are most sensitive to sound underwater...

  15. The aquatic tympanic ear: convergent adaptations for underwater hearing in three tetrapods

    DEFF Research Database (Denmark)

    Christensen-Dalsgaard, Jakob; Wahlberg, Magnus; Larsen, Ole Næsbye

    pressure, low particle motion medium, and the consequence is that an efficient underwater ear is sensitive to sound pressure. It is often stated that underwater hearing can work efficiently without a middle ear apparatus by bone conduction, since sound is transmitted from water to inner ear tissue...... with little loss. However, the sensitivity of such an ear is limited by the very low particle motion in water. We report on underwater hearing in tetrapods ranging from totally aquatic (the clawed frog Xenopus laevis) and mostly aquatic (the red-eared slider Trachemys scripta) to mostly terrestrial (the...... is modified (cartilaginous or partly cartilaginous). In all three species, the lowest threshold to underwater sound is at this peak frequency and is around 80 dB re 1 µPa. The sensitivity to sound pressure is slightly lower in water than in air, making underwater hearing much more efficient in terms of sound...

  16. Discovery of Sound in the Sea: Resources for Educators, Students, the Public, and Policymakers.

    Science.gov (United States)

    Vigness-Raposa, Kathleen J; Scowcroft, Gail; Miller, James H; Ketten, Darlene R; Popper, Arthur N

    2016-01-01

    There is increasing concern about the effects of underwater sound on marine life. However, the science of sound is challenging. The Discovery of Sound in the Sea (DOSITS) Web site ( http://www.dosits.org ) was designed to provide comprehensive scientific information on underwater sound for the public and educational and media professionals. It covers the physical science of underwater sound and its use by people and marine animals for a range of tasks. Celebrating 10 years of online resources, DOSITS continues to develop new material and improvements, providing the best resource for the most up-to-date information on underwater sound and its potential effects.

  17. The Flexible Bass Absorber

    DEFF Research Database (Denmark)

    Adelman-Larsen, Niels Werner; Thompson, Eric Robert; Gade, Anders Christian

    2007-01-01

    Multi-purpose concert halls face a dilemma. They host different performance types that require significantly different acoustic conditions in order to provide the best sound quality to both the performers, sound engineers and the audience. Pop and rock music often contain high levels of bass sound...... energy but still require high definition for good sound quality. The mid- and high-frequency absorption is easily regulated, but adjusting the low-frequency absorption has typically been too expensive or requires too much space to be practical for multi-purpose halls. A practical solution to this dilemma...... has been developed. Measurements were made on a variable and mobile low-frequency absorber. The paper presents the results of prototype sound absorption measurements as well as elements of the design....

  18. The Flexible Bass Absorber

    DEFF Research Database (Denmark)

    Adelman-Larsen, Niels Werner; Thompson, Eric Robert; Gade, Anders Christian

    2007-01-01

    Multi-purpose concert halls face a dilemma. They host different performance types that require significantly different acoustic conditions in order to provide the best sound quality to both the performers, sound engineers and the audience. Pop and rock music often contains high levels of bass sound...... energy but still require high definition for good sound quality. The mid- and high-frequency absorption is easily regulated, but adjusting the low-frequency absorption has typically been too expensive or requires too much space to be practical for multi-purpose halls. A practical solution to this dilemma...... has been developed. Measurements were made on a variable and mobile low-frequency absorber. The paper presents the results of prototype sound absorption measurements as well as elements of the design....

  19. Biophysics of underwater hearing in the clawed frog, Xenopus laevis

    DEFF Research Database (Denmark)

    Christensen-Dalsgaard, J; Elepfandt, A

    1995-01-01

    Anesthetized clawed frogs (Xenopus laevis) were stimulated with underwater sound and the tympanic disk vibrations were studied using laser vibrometry. The tympanic disk velocities ranged from 0.01 to 0.5 mm/s (at a sound pressure of 2 Pa) in the frequency range of 0.4-4 kHz and were 20-40 dB higher...

  20. Sound absorption of snow

    OpenAIRE

    Maysenhölder, W.; Schneebeli, M.; Zhou, X.; Zhang, T.; Heggli, M.

    2008-01-01

    Recently fallen snow possesses good sound-absorbing properties. This fact is well-known and confirmed by measurements. Is the filigree structure of snowflakes decisive? In principle we know that the sound-absorbing capacity of a porous material is dependent on its structure. But until now the question as to which structural characteristics are significant has been insufficiently answered. Detailed investigations of snow are to explain this fact by precise measurements of the sound absorption,...

  1. The Impact of Offshore Wind Turbines on Underwater Ambient Noise Levels

    OpenAIRE

    Glegg, Stewart

    2015-01-01

    The underwater sound levels generated by offshore wind turbine farms is a concern because of the possible environmental impact on marine mammals. This paper will consider how sound generated by a wind turbine is transmitted into a shallow water channel. It is shown that the underwater sound levels can be calculated for a typical offshore wind turbine by using the theory of Chapman and Ward (1990) combined with aeroacoustic models of trailing edge noise on the wind turbine blades. A procedure ...

  2. Shock absorber

    International Nuclear Information System (INIS)

    Housman, J.J.

    1978-01-01

    A shock absorber is described for use in a hostile environment at the end of a blind passage for absorbing impact loads. The shock absorber includes at least one element which occupies the passage and which is comprised of a porous brittle material which is substantially non-degradable in the hostile environment. A void volume is provided in the element to enable the element to absorb a predetermined level of energy upon being crushed due to impact loading

  3. Underwater Geotechnical Foundations

    National Research Council Canada - National Science Library

    Lee, Landris

    2001-01-01

    This report provides an overview and description of the design and construction of underwater geotechnical foundations and offers preliminary guidance based on past and current technology applications...

  4. Design and Analysis of Underwater Acoustic Networks with Reflected Links

    Science.gov (United States)

    Emokpae, Lloyd

    Underwater acoustic networks (UWANs) have applications in environmental state monitoring, oceanic profile measurements, leak detection in oil fields, distributed surveillance, and navigation. For these applications, sets of nodes are employed to collaboratively monitor an area of interest and track certain events or phenomena. In addition, it is common to find autonomous underwater vehicles (AUVs) acting as mobile sensor nodes that perform search-and-rescue missions, reconnaissance in combat zones, and coastal patrol. These AUVs are to work cooperatively to achieve a desired goal and thus need to be able to, in an ad-hoc manner, establish and sustain communication links in order to ensure some desired level of quality of service. Therefore, each node is required to adapt to environmental changes and be able to overcome broken communication links caused by external noise affecting the communication channel due to node mobility. In addition, since radio waves are quickly absorbed in the water medium, it is common for most underwater applications to rely on acoustic (or sound) rather than radio channels for mid-to-long range communications. However, acoustic channels pose multiple challenging issues, most notably the high transmission delay due to slow signal propagation and the limited channel bandwidth due to high frequency attenuation. Moreover, the inhomogeneous property of the water medium affects the sound speed profile while the signal surface and bottom reflections leads to multipath effects. In this dissertation, we address these networking challenges by developing protocols that take into consideration the underwater physical layer dynamics. We begin by introducing a novel surface-based reflection scheme (SBR), which takes advantage of the multipath effects of the acoustic channel. SBR works by using reflections from the water surface, and bottom, to establish non-line-of-sight (NLOS) communication links. SBR makes it possible to incorporate both line

  5. Evaluating underwater noise regulations for piling noise in Belgium and The Netherlands

    OpenAIRE

    Rumes, B.; Erkman, A.; Haelters, J.

    2016-01-01

    There is concern about possible effects on the marine ecosystem of high levels of underwater noise generated during pile driving for the construction of offshore wind farms. As a result, various national governments in Europe have identified limits of underwater sound levels, as such imposing in many cases the use of noise mitigation measures. In this paper we compare the regulations with regard to impulsive underwater noise in the Belgian wind farm zone with those in the Dutch wind energy zo...

  6. Marine Animal Sound Database. Twelve Years of Tracking 52-Hz Whale Calls from a Unique Source in the North Pacific

    National Research Council Canada - National Science Library

    Watkins, William

    2004-01-01

    Long-term monitoring of underwater sounds using U.S. Navy SOSUS and other hydrophone arrays allowed us to follow the seasonal distribution of underwater calls produced by blue, fin and humpback whales across the North Pacific...

  7. Arctic Climate Observations Using Underwater Sound (ACOUS)

    Science.gov (United States)

    1997-09-30

    of the ice cover in the Arctic Ocean. ACOUS will provide data on the large thermohaline change now occurring in the Arctic Ocean, and advance the...at UAF for a simulation period of 47 years. Two general regimes of circulation with a 15-year period were discovered . Anti-cyclonic circulation

  8. Underwater Scene Composition

    Science.gov (United States)

    Kim, Nanyoung

    2009-01-01

    In this article, the author describes an underwater scene composition for elementary-education majors. This project deals with watercolor with crayon or oil-pastel resist (medium); the beauty of nature represented by fish in the underwater scene (theme); texture and pattern (design elements); drawing simple forms (drawing skill); and composition…

  9. Passive aquatic listener (PAL): An adoptive underwater acoustic recording system for the marine environment

    International Nuclear Information System (INIS)

    Anagnostou, Marios N.; Nystuen, Jeffrey A.; Anagnostou, Emmanouil N.; Papadopoulos, Anastasios; Lykousis, Vassilios

    2011-01-01

    The ambient sound field in the ocean is a combination of natural and manmade sounds. Consequently, the interpretation of the ambient sound field can be used to quantify these processes. In the frequency range from 1 to 50 kHz, the general character of ocean ambient sound is a slowly changing background that is closely associated with local wind speed, interspersed with shorter time scale events such as rain storms, ships and animal calls. At lower frequencies the underwater ambient sound budget includes geologically generated sound activities including underwater volcanic eruptions, seismic and seepage faults that generate bubbles, etc. that can also potentially be classified and quantified. Acoustic data are collected on hydrophones. Hydrophones are simple, robust sensors that can be deployed on most ocean instrumentation systems including surface or sub-surface moorings, bottom mounted systems, drifters, ARGO floats or autonomous underwater platforms. A dedicated oceanic underwater recorder called a passive acoustic listener (PAL) has been developed. A principal issue is to accurately distinguish different sound sources so that they can be quantified as part of a sound budget, and then quantified if appropriate. Based on ongoing data collected from the Poseidon II network the retrieval potential of multi-parameters from underwater sound, including meteorological (i.e., precipitation and winds) and in general geophysical, anthropogenetic (i.e., ships, submarines, etc.) and biological (whales, etc.) sources is presented.

  10. A Brief Review of Anthropogenic Sound in the Oceans

    OpenAIRE

    Studds, Gerry E; Wright, Andrew J

    2007-01-01

    Sound in the oceans is generated by a variety of natural sources, such as breaking waves, rain, and marine animals, as well as a variety of human-produced sources, such as ships, sonars and seismic signals. This overview will begin with a quick review of some basic properties of sound waves with particular reference to differences between the behaviours of these waves underwater versus in air. A basic understanding of the physics of underwater sound is critical to understanding how marine ani...

  11. Underwater Noise Modelling of Wave Energy Devices

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2009-07-01

    Future large-scale implementation of wave energy converts (WECs) will introduce an anthropogenic activity in the ocean which may contribute to underwater noise. The Ocean houses several marine species with acoustic sensibility; consequently the potential impact of the underwater noise needs to be addressed. At present, there are no acoustic impact studies based on acquired data. The WEAM project (Wave Energy Acoustic Monitoring) aims at developing an underwater noise monitoring plan for WECs. The development of an acoustic monitoring plan must consider the sound propagation in the ocean, identify noise sources, understand the operational characteristics and select adequate instrumentation. Any monitoring strategy must involve in-situ measurements. However, the vast distances which sound travels within the ocean, can make in-situ measurements covering the entire area of interest, impracticable. This difficulty can be partially overcome through acoustic numerical modelling. This paper presents a synthetic study, on the application of acoustic forward modelling and the evaluation of the impact of noise produced by wave energy devices on marine mammals using criteria based on audiograms of dolphins, or other species. The idea is to illustrate the application of that methodology, and to show to what extent it allows for estimating distances of impacts due to acoustic noise.

  12. Underwater 3D filming

    Directory of Open Access Journals (Sweden)

    Roberto Rinaldi

    2014-12-01

    Full Text Available After an experimental phase of many years, 3D filming is now effective and successful. Improvements are still possible, but the film industry achieved memorable success on 3D movie’s box offices due to the overall quality of its products. Special environments such as space (“Gravity” and the underwater realm look perfect to be reproduced in 3D. “Filming in space” was possible in “Gravity” using special effects and computer graphic. The underwater realm is still difficult to be handled. Underwater filming in 3D was not that easy and effective as filming in 2D, since not long ago. After almost 3 years of research, a French, Austrian and Italian team realized a perfect tool to film underwater, in 3D, without any constrains. This allows filmmakers to bring the audience deep inside an environment where they most probably will never have the chance to be.

  13. Underwater Glider System Study

    OpenAIRE

    Jenkins, Scott A; Humphreys, Douglas E; Sherman, Jeff; Osse, Jim; Jones, Clayton; Leonard, Naomi; Graver, Joshua; Bachmayer, Ralf; Clem, Ted; Carroll, Paul; Davis, Philip; Berry, Jon; Worley, Paul; Wasyl, Joseph

    2003-01-01

    The goals of this study are to determine how to advance from present capabilities of underwater glider (and hybrid motorglider) technology to what could be possible within the next few years; and to identify critical research issues that must be resolved to make such advancements possible. These goals were pursued by merging archival flight data with numerical model results and system spreadsheet analysis to extrapolate from the present state-of-the–art in underwater (UW) gliders to potential...

  14. Offshore dredger sounds: Source levels, sound maps, and risk assessment

    NARCIS (Netherlands)

    Jong, C.A.F. de; Ainslie, M.A.; Heinis, F.; Janmaat, J.

    2016-01-01

    The underwater sound produced during construction of the Port of Rotterdam harbor extension (Maasvlakte 2) was measured, with emphasis on the contribution of the trailing suction hopper dredgers during their various activities: dredging, transport, and discharge of sediment. Measured source levels

  15. Cymbal and BB underwater transducers and arrays

    Energy Technology Data Exchange (ETDEWEB)

    Newnham, R.E.; Zhang, J.; Alkoy, S.; Meyer, R.; Hughes, W.J.; Hladky-Hennion, A.C.; Cochran, J.; Markley, D. [Materials Research Laboratory, Penn State University, University Park, PA 16802 (United States)

    2002-09-01

    The cymbal is a miniaturized class V flextensional transducer that was developed for use as a shallow water sound projector and receiver. Single elements are characterized by high Q, low efficiency, and medium power output capability. Its low cost and thin profile allow the transducer to be assembled into large flexible arrays. Efforts were made to model both single elements and arrays using the ATILA code and the integral equation formulation (EQI).Millimeter size microprobe hydrophones (BBs) have been designed and fabricated from miniature piezoelectric hollow ceramic spheres for underwater applications such as mapping acoustic fields of projectors, and flow noise sensors for complex underwater structures. Green spheres are prepared from soft lead zirconate titanate powders using a coaxial nozzle slurry process. A compact hydrophone with a radially-poled sphere is investigated using inside and outside electrodes. Characterization of these hydrophones is done through measurement of hydrostatic piezoelectric charge coefficients, free field voltage sensitivities and directivity beam patterns. (orig.)

  16. Sound absorption of a rib-stiffened plate covered by anechoic coatings.

    Science.gov (United States)

    Fu, Xinyi; Jin, Zhongkun; Yin, Yao; Liu, Bilong

    2015-03-01

    Underwater vehicles are often equipped with anechoic coatings to absorb the sound waves of active sonar and attenuate the noise emitted from the vessels. Rubber layers with periodically distributed air cavities are widely used as anechoic coatings. In this paper, the sound absorption of anechoic coatings embedded with doubly periodic cavities and backed with periodically rib-stiffened plates is investigated using a finite element method (FEM) with Bloch-periodic boundary conditions. Numerical results given by the FEM are compared with those of a simplified transfer impedance approach to explain the shifting of the main absorption peak. Further a simplified FEM approach, which reduces calculation time significantly and maintains the reasonable accuracy, is proposed for a comparison. The results indicate that the plate and the ribs can have significant impacts on the absorption performance of anechoic coatings, especially at low frequencies.

  17. Definition and results of test cases for shipping sound maps

    NARCIS (Netherlands)

    Colin,M.E.G.D.; Ainslie, M.A.; Binnerts, B.; Jong, C.A.F. de; Karasalo, I.; Östberg, M.; Sertlek, H.O.; Folegot, T.; Clorennec, D.

    2015-01-01

    The SONIC (Suppression Of underwater Noise Induced by Cavitation) and AQUO (Achieve QUieter Oceans by shipping noise footprint reduction) projects were awarded within the European Seventh Framework Program to develop tools to investigate and mitigate the effects of underwater sound generated by

  18. Sound and sound sources

    DEFF Research Database (Denmark)

    Larsen, Ole Næsbye; Wahlberg, Magnus

    2017-01-01

    There is no difference in principle between the infrasonic and ultrasonic sounds, which are inaudible to humans (or other animals) and the sounds that we can hear. In all cases, sound is a wave of pressure and particle oscillations propagating through an elastic medium, such as air. This chapter...... is about the physical laws that govern how animals produce sound signals and how physical principles determine the signals’ frequency content and sound level, the nature of the sound field (sound pressure versus particle vibrations) as well as directional properties of the emitted signal. Many...... of these properties are dictated by simple physical relationships between the size of the sound emitter and the wavelength of emitted sound. The wavelengths of the signals need to be sufficiently short in relation to the size of the emitter to allow for the efficient production of propagating sound pressure waves...

  19. Underwater Optical Wireless Channel Modeling Using Monte-Carlo Method

    Science.gov (United States)

    Saini, P. Sri; Prince, Shanthi

    2011-10-01

    At present, there is a lot of interest in the functioning of the marine environment. Unmanned or Autonomous Underwater Vehicles (UUVs or AUVs) are used in the exploration of the underwater resources, pollution monitoring, disaster prevention etc. Underwater, where radio waves do not propagate, acoustic communication is being used. But, underwater communication is moving towards Optical Communication which has higher bandwidth when compared to Acoustic Communication but has shorter range comparatively. Underwater Optical Wireless Communication (OWC) is mainly affected by the absorption and scattering of the optical signal. In coastal waters, both inherent and apparent optical properties (IOPs and AOPs) are influenced by a wide array of physical, biological and chemical processes leading to optical variability. The scattering effect has two effects: the attenuation of the signal and the Inter-Symbol Interference (ISI) of the signal. However, the Inter-Symbol Interference is ignored in the present paper. Therefore, in order to have an efficient underwater OWC link it is necessary to model the channel efficiently. In this paper, the underwater optical channel is modeled using Monte-Carlo method. The Monte Carlo approach provides the most general and most flexible technique for numerically solving the equations of Radiative transfer. The attenuation co-efficient of the light signal is studied as a function of the absorption (a) and scattering (b) coefficients. It has been observed that for pure sea water and for less chlorophyll conditions blue wavelength is less absorbed whereas for chlorophyll rich environment red wavelength signal is absorbed less comparative to blue and green wavelength.

  20. Underwater Noise from a Wave Energy Converter Is Unlikely to Affect Marine Mammals.

    Directory of Open Access Journals (Sweden)

    Jakob Tougaard

    Full Text Available Underwater noise was recorded from the Wavestar wave energy converter; a full-scale hydraulic point absorber, placed on a jack-up rig on the Danish North Sea coast. Noise was recorded 25 m from the converter with an autonomous recording unit (10 Hz to 20 kHz bandwidth. Median sound pressure levels (Leq in third-octave bands during operation of the converter were 106-109 dB re. 1 μPa in the range 125-250 Hz, 1-2 dB above ambient noise levels (statistically significant. Outside the range 125-250 Hz the noise from the converter was undetectable above the ambient noise. During start and stop of the converter a more powerful tone at 150 Hz (sound pressure level (Leq 121-125 dB re 1 μPa was easily detectable. This tone likely originated from the hydraulic pump which was used to lower the absorbers into the water and lift them out of the water at shutdown. Noise levels from the operating wave converter were so low that they would barely be audible to marine mammals and the likelihood of negative impact from the noise appears minimal. A likely explanation for the low noise emissions is the construction of the converter where all moving parts, except for the absorbers themselves, are placed above water on a jack-up rig. The results may thus not be directly transferable to other wave converter designs but do demonstrate that it is possible to harness wave energy without noise pollution to the marine environment.

  1. Underwater Noise from a Wave Energy Converter Is Unlikely to Affect Marine Mammals.

    Science.gov (United States)

    Tougaard, Jakob

    2015-01-01

    Underwater noise was recorded from the Wavestar wave energy converter; a full-scale hydraulic point absorber, placed on a jack-up rig on the Danish North Sea coast. Noise was recorded 25 m from the converter with an autonomous recording unit (10 Hz to 20 kHz bandwidth). Median sound pressure levels (Leq) in third-octave bands during operation of the converter were 106-109 dB re. 1 μPa in the range 125-250 Hz, 1-2 dB above ambient noise levels (statistically significant). Outside the range 125-250 Hz the noise from the converter was undetectable above the ambient noise. During start and stop of the converter a more powerful tone at 150 Hz (sound pressure level (Leq) 121-125 dB re 1 μPa) was easily detectable. This tone likely originated from the hydraulic pump which was used to lower the absorbers into the water and lift them out of the water at shutdown. Noise levels from the operating wave converter were so low that they would barely be audible to marine mammals and the likelihood of negative impact from the noise appears minimal. A likely explanation for the low noise emissions is the construction of the converter where all moving parts, except for the absorbers themselves, are placed above water on a jack-up rig. The results may thus not be directly transferable to other wave converter designs but do demonstrate that it is possible to harness wave energy without noise pollution to the marine environment.

  2. "Boxnep" advanced modular underwater robot

    OpenAIRE

    Buluev, Ilia

    2016-01-01

    The article discusses the relevance of the underwater vehicles' ability to solve a wide range of problems. The idea put in the basis of this research is designing a modular underwater robot. It allows to mount various equipment and test it in underwater environment. The paper deals with the concept of the robot and its characteristics.

  3. Resources for Underwater Robotics Education

    Science.gov (United States)

    Wallace, Michael L.; Freitas, William M.

    2016-01-01

    4-H clubs can build and program underwater robots from raw materials. An annotated resource list for engaging youth in building underwater remotely operated vehicles (ROVs) is provided. This article is a companion piece to the Research in Brief article "Building Teen Futures with Underwater Robotics" in this issue of the "Journal of…

  4. Underwater detection by using ultrasonic sensor

    Science.gov (United States)

    Bakar, S. A. A.; Ong, N. R.; Aziz, M. H. A.; Alcain, J. B.; Haimi, W. M. W. N.; Sauli, Z.

    2017-09-01

    This paper described the low cost implementation of hardware and software in developing the system of ultrasonic which can visualize the feedback of sound in the form of measured distance through mobile phone and monitoring the frequency of detection by using real time graph of Java application. A single waterproof transducer of JSN-SR04T had been used to determine the distance of an object based on operation of the classic pulse echo detection method underwater. In this experiment, the system was tested by placing the housing which consisted of Arduino UNO, Bluetooth module of HC-06, ultrasonic sensor and LEDs at the top of the box and the transducer was immersed in the water. The system which had been tested for detection in vertical form was found to be capable of reporting through the use of colored LEDs as indicator to the relative proximity of object distance underwater form the sensor. As a conclusion, the system can detect the presence of an object underwater within the range of ultrasonic sensor and display the measured distance onto the mobile phone and the real time graph had been successfully generated.

  5. Sound Hole Sound

    OpenAIRE

    Politzer, David

    2015-01-01

    The volume of air that goes in and out of a musical instrument's sound hole is related to the sound hole's contribution to the volume of the sound. Helmholtz's result for the simplest case of steady flow through an elliptical hole is reviewed. Measurements on multiple holes in sound box geometries and scales relevant to real musical instruments demonstrate the importance of a variety of effects. Electric capacitance of single flat plates is a mathematically identical problem, offering an alte...

  6. Room Modal Equalisation with Electroacoustic Absorbers

    OpenAIRE

    Rivet, Etienne Thierry Jean-Luc

    2016-01-01

    The sound quality in a room is of fundamental importance for both recording and reproducing processes. Because of the room modes, the distributions in space and frequency of the sound field are largely altered. Excessive rise and decay times caused by the resonances might even mask some details at higher frequencies, and these irregularities may be heard as a coloration of the sound. To address this problem, passive absorbers are bulky and too inefficient to significantly improve the listen...

  7. Underwater Wireless Acousto-Optic Waveguide (UWAOW)

    Science.gov (United States)

    Giuliano, Giovanni; Kent, Lionel W. J.; Laycock, Leslie C.

    2017-10-01

    The present study originated in the lack of research into achieving underwater total internal reflection (TIR) via the acousto-optic effect. The uniqueness of this technique exists in the fact that it is based on a high sound pressure level which induces a localised change in refractive index of seawater sufficient to achieve total internal reflection within the communication channel. Different transducer systems for generating the pressure wave have been investigated and take the form of a wave which may be either a standing wave, or a novel beamforming technique. The former is based on an array of transducers and with an acoustic mirror at the receiver in order to establish the standing wave. The alternative approach relies on the high intrinsic directionality of a novel beamformer where an annular transducer array is examined as an acoustic source. In this paper, the main characteristics of the acoustic optic waveguide will be presented. This will include both sound and light propagation in the ocean, TIR, novel beam propagation, the refractive index of water as a function of the externally applied acoustic pressure, and the acoustic technology. The modelled results, the limitations imposed by the challenging medium, and the system requirements required to obtain an Underwater Wireless Acousto-Optic Waveguide (UWAOW) will be also addressed.

  8. Underwater laser detection system

    Science.gov (United States)

    Gomaa, Walid; El-Sherif, Ashraf F.; El-Sharkawy, Yasser H.

    2015-02-01

    The conventional method used to detect an underwater target is by sending and receiving some form of acoustic energy. But the acoustic systems have limitations in the range resolution and accuracy; while, the potential benefits of a laserbased underwater target detection include high directionality, high response, and high range accuracy. Lasers operating in the blue-green region of the light spectrum(420 : 570nm)have a several applications in the area of detection and ranging of submersible targets due to minimum attenuation through water ( less than 0.1 m-1) and maximum laser reflection from estimated target (like mines or submarines) to provide a long range of detection. In this paper laser attenuation in water was measured experimentally by new simple method by using high resolution spectrometer. The laser echoes from different targets (metal, plastic, wood, and rubber) were detected using high resolution CCD camera; the position of detection camera was optimized to provide a high reflection laser from target and low backscattering noise from the water medium, digital image processing techniques were applied to detect and discriminate the echoes from the metal target and subtract the echoes from other objects. Extraction the image of target from the scattering noise is done by background subtraction and edge detection techniques. As a conclusion, we present a high response laser imaging system to detect and discriminate small size, like-mine underwater targets.

  9. Underwater Gliders: A Review

    Directory of Open Access Journals (Sweden)

    Javaid Muhammad Yasar

    2014-07-01

    Full Text Available Underwater gliders are a type of underwater vehicle that transverse the oceans by shifting its buoyancy, during which its wings develop a component of the downward motion in the horizontal plane, thus producing a forward force. They are primarily used in oceanography sensing and data collection and play an important role in ocean research and development. Although there have been considerable developments in these gliders since the development of the first glider concept in 1989, to date, no review of these gliders have been done. This paper reviews existing underwater gliders, with emphasis on their respective working principles, range and payload capacity. All information on gliders available in the public domain or published in literature from the year 2000-2013 was reviewed. The majority of these gliders have an operational depth of 1000 m and a payload of less than 25 kg. The exception is a blend-body shape glider, which has a payload of approximately 800 kg and an operational depth around about 300 m. However, the commercialization of these gliders has been limited with only three know examples that have been successfully commercialized.

  10. In-air and underwater hearing of the cormorant

    DEFF Research Database (Denmark)

    Larsen, Ole Næsbye; Wahlberg, Magnus; Christensen-Dalsgaard, Jakob

    Numerous studies have mapped the hearing abilities of birds in air but currently there is little or no data on how diving birds hear or react to sound under water. Therefore, it is unknown whether the ears and auditory system of diving birds are adapted to underwater hearing. In the present study...... 10 cm under water in a large water filled-tank while being artificially ventilated. ABR-responses to calibrated tone bursts produced by a woofer and an underwater speaker, respectively, were measured at different intensities and frequencies to obtain hearing threshold values in air and under water......Hz) under water. Generally, the cormorant ear was not very sensitive to sound, neither in air nor under water. The hearing abilities in water, however, were better than what would have been expected for a purely in-air adapted ear. (Supported by the Carlsberg Foundation 2009_01_0292 and the Danish Council...

  11. Sound absorption of porous metals at high sound pressure levels.

    Science.gov (United States)

    Wang, Xiaolin; Peng, Feng; Chang, Baojun

    2009-08-01

    This paper is a study about sound absorption properties of porous metals at high sound pressure levels. A method of deriving the nonlinear static flow resistance for highly porous fibrous metals is proposed by solving Oseen's equation to take account of the inertia effect, validated by experiments of airflow measurement. In order to predict nonlinear sound absorbing performance of a finite thickness porous metal layer, a numerical method is employed, verified by sound absorption measurement in an impedance tube. Accordingly, the effects of the nonlinear coefficient on the porous metal sound absorption are investigated.

  12. Underwater gas tornado

    Science.gov (United States)

    Byalko, Alexey V.

    2013-07-01

    We present the first experimental observation of a new hydrodynamic phenomenon, the underwater tornado. Simple measurements show that the tornado forms a vortex of the Rankine type, i.e. the rising gas rotates as a solid body and the liquid rotates with a velocity decreasing hyperbolically with the radius. We obtain the dependence of the tornado radius a on the gas stream value j theoretically: a ∼ j2/5. Processing of a set of experiments yielded the value 0.36 for the exponent in this expression. We also report the initial stages of the theoretical study of this phenomenon.

  13. Hydrogel microphones for stealthy underwater listening

    Science.gov (United States)

    Gao, Yang; Song, Jingfeng; Li, Shumin; Elowsky, Christian; Zhou, You; Ducharme, Stephen; Chen, Yong Mei; Zhou, Qin; Tan, Li

    2016-08-01

    Exploring the abundant resources in the ocean requires underwater acoustic detectors with a high-sensitivity reception of low-frequency sound from greater distances and zero reflections. Here we address both challenges by integrating an easily deformable network of metal nanoparticles in a hydrogel matrix for use as a cavity-free microphone. Since metal nanoparticles can be densely implanted as inclusions, and can even be arranged in coherent arrays, this microphone can detect static loads and air breezes from different angles, as well as underwater acoustic signals from 20 Hz to 3 kHz at amplitudes as low as 4 Pa. Unlike dielectric capacitors or cavity-based microphones that respond to stimuli by deforming the device in thickness directions, this hydrogel device responds with a transient modulation of electric double layers, resulting in an extraordinary sensitivity (217 nF kPa-1 or 24 μC N-1 at a bias of 1.0 V) without using any signal amplification tools.

  14. OFDM for underwater acoustic communications

    CERN Document Server

    Zhou, Shengli

    2014-01-01

    A blend of introductory material and advanced signal processing and communication techniques, of critical importance to underwater system and network development This book, which is the first to describe the processing techniques central to underwater OFDM, is arranged into four distinct sections: First, it describes the characteristics of underwater acoustic channels, and stresses the difference from wireless radio channels. Then it goes over the basics of OFDM and channel coding. The second part starts with an overview of the OFDM receiver, and develops various modules for the receiver des

  15. Utgrunden off-shore wind farm - Measurements of underwater noise

    International Nuclear Information System (INIS)

    Lindell, Hans

    2003-07-01

    Airicole, GE Wind Energy and SEAS/Energi E2 have initiated this project in order to achieve a better understanding on how offshore based wind farms effect the underwater noise. The main reason is to gain knowledge on how marine wildlife could be effected by this kind of installation. The measurements were performed at Utgrunden wind farm that is situated at the reef Utgrunden on the Swedish southeast coast. The farm consists of seven 1,5 MW turbines. Three hydrophones registered the underwater sound and four accelerometers the tower vibrations. The measurement campaign was conducted during a period from November 2002 to February 2003. The objectives with this project is to answer the following issues and its results are: 1. What is the character of sound from a single power station? - The turbines radiate sound mainly at a few dominating frequencies from 30 Hz up to 800 Hz. At frequencies below 3 Hz no contribution from the turbines can be detected due to the high background level from the waves and the low tower vibration level. 2. What are the sound generating mechanisms in the turbine? - Gearbox mesh frequency vibrations that are transmitted via the tower structure and radiated out to the water mainly generate the sound. Airborne blade sound is effectively dampened in the transition from air to water. 3. How does the sound attenuate with increasing distance at different frequencies? - The average attenuation per doubled distance for frequencies between 31 Hz and 722 Hz is approximately 4 dB in the measured positions. No clear frequency dependence could be found. 4. How does the sound pressure level vary with increasing wind speed? - With increasing wind speed, the sound pressure level increases and the dominating frequencies move upward due to increasing turbine rotational speed. 5. How does sound from different power stations interfere with each other and influence the over all sound image? - No clear tendencies of interference could be observed in this study

  16. Hemispherical optical dome for underwater communication

    Science.gov (United States)

    Shiri, Ron S.; Lunde, Emily L.; Coronado, Patrick L.; Quijada, Manuel A.

    2017-08-01

    For many years, acoustic systems have been used as the primary method for underwater communication; however, the data transfer rate of such systems is low because sound propagates slowly through water. A higher throughput can be achieved using visible light to transmit data underwater. The first issue with this approach is that there is generally a large loss of the light signal due to scattering and absorption in water, even though there is an optimal wavelength for transmission in the blue or green wavelengths of the visible spectrum. The second issue is that a simple communication system, consisting only of a highly directional source/transmitter and small optical detector/receiver, has a very narrow field of view. The goal of this project is to improve an optical, underwater communication system by increasing the effective field of view of the receiving optics. To this end, we make two changes to the simple system: (1) An optical dome was added near the receiver. An array of lenses is placed radially on the surface of the dome, reminiscent of the compound eye of an insect. The lenses make the source and detector planes conjugate, and each lens adds a new region of the source plane to the instrument's total field of view. (2) The receiver was expanded to include multiple photodiodes. With these two changes, the receiver has much more tolerance to misalignments (in position and angle) of the transmitter. Two versions of the optical dome (with 6" and 8" diameters) were designed using PTC's Creo CAD software and modeled using Synopsys' CODE V optical design software. A series of these transparent hemispherical domes, with both design diameters, were manufactured using a 5-axis mill. The prototype was then retrofitted with lenses and compared with the computer-generated model to demonstrate the effectiveness of this solution. This work shows that the dome design improves the optical field of view of the underwater communication system considerably. Furthermore, with

  17. Foley Sounds vs Real Sounds

    DEFF Research Database (Denmark)

    Trento, Stefano; Götzen, Amalia De

    2011-01-01

    This paper is an initial attempt to study the world of sound effects for motion pictures, also known as Foley sounds. Throughout several audio and audio-video tests we have compared both Foley and real sounds originated by an identical action. The main purpose was to evaluate if sound effects are...... applications of sound design such as advertisement or soundtracks for movies....

  18. Underwater soundscape of marine protected areas in the south Brazilian coast.

    Science.gov (United States)

    Sánchez-Gendriz, I; Padovese, L R

    2016-04-15

    The Laje de Santos Marine State Park (LSMSP) and Xixová-Japuí State Park (XJSP) are two protected areas (PA), close to the Santos Bay in the south Brazilian coast. The region encompasses both important biodiversity and anthropogenic activities. This study aims to serve as a first reference survey of the underwater soundscape of these PAs. Additionally it evaluates the presence of the anthropogenic and biological sound in these areas. One month of continuous recorded underwater sound, at selected locations in XJSP and LSMSP, is used in this study. The data were characterized by its spectral content and by the temporal evolution of Sound Pressure Levels (SPL). Both locations showed sound events with daily periodicities, mainly related with boats and fish chorus. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Discovery of Sound in the Sea 2014 Annual Report

    Science.gov (United States)

    2014-09-30

    a false killer whale was able to reduce its hearing sensitivity when a warning sound preceded a loud sound. The DOSITS team will continue to scan...will investigate noise exposure and marine animals, highlighting hearing sensititivies across taxa, potential behavioral effects of underwater sound...bottlenose whales , and dugongs are in development for the DOSITS Audio Gallery. In addition, longer audio files continue to be added when possible. B

  20. Underwater plasma arc cutting

    International Nuclear Information System (INIS)

    Leautier, R.; Pilot, G.

    1991-01-01

    This report describes the work done to develop underwater plasma arc cutting techniques, to characterise aerosols from cutting operations on radioactive and non-radioactive work-pieces, and to develop suitable ventilation and filtration techniques. The work has been carried out in the framework of a contract between CEA-CEN Cadarache and the Commission of European Communities. Furthermore, this work has been carried out in close cooperation with CEA-CEN Saclay mainly for secondary emissions and radioactive analysis. The contract started in May 1986 and was completed in December 1988 by a supplementary agreement. This report has been compiled from several progress reports submitted during the work period, contains the main findings of the work and encloses the results of comparative tests on plasma arc cutting

  1. Manufacture of stabilized phosphogypsum blocks for underwater massives in the Gulf of Gabès

    Directory of Open Access Journals (Sweden)

    Koubaa Lobna

    2014-04-01

    Studies show that the treatment of PH in the crushed sand and cement or cement and lime gives the best results in terms of ultrasonic speed and compressive strength. Also, they indicate that the addition of cement and lime can absorb huge amounts of PH (92 %. Resistance obtained is sufficient for possible use blocks of PH made for the construction of massive underwater.

  2. Safety aspects for underwater vehicles

    Digital Repository Service at National Institute of Oceanography (India)

    Madhan, R.; Navelkar, G.S.; Desa, E.S.; Afzulpurkar, S.; Prabhudesai, S.P.; Dabholkar, N.; Mascarenhas, A.A.M.Q.; Maurya, P.

    . This stresses for implementation of multiple safety measures of a high degree so that the platform operates continuously in a fail-safe mode. This paper discusses issues on safety measures implemented on the autonomous underwater platforms namely MAYA AUV...

  3. Wide-band underwater acoustic absorption based on locally resonant unit and interpenetrating network structure

    International Nuclear Information System (INIS)

    Heng, Jiang; Mi-Lin, Zhang; Yu-Ren, Wang; Yan-Ping, Hu; Ding, Lan; Qun-Li, Wu; Huan-Tong, Lu

    2010-01-01

    The interpenetrating network structure provides an interesting avenue to novel materials. Locally resonant phononic crystal (LRPC) exhibits excellent sound attenuation performance based on the periodical arrangement of sound wave scatters. Combining the LRPC concept and interpenetrating network glassy structure, this paper has developed a new material which can achieve a wide band underwater strong acoustic absorption. Underwater absorption coefficients of different samples were measured by the pulse tube. Measurement results show that the new material possesses excellent underwater acoustic effects in a wide frequency range. Moreover, in order to investigate impacts of locally resonant units, some defects are introduced into the sample. The experimental result and the theoretical calculation both show that locally resonant units being connected to a network structure play an important role in achieving a wide band strong acoustic absorption. (condensed matter: structure, thermal and mechanical properties)

  4. Underwater optical wireless communication network

    Science.gov (United States)

    Arnon, Shlomi

    2010-01-01

    The growing need for underwater observation and subsea monitoring systems has stimulated considerable interest in advancing the enabling technologies of underwater wireless communication and underwater sensor networks. This communication technology is expected to play an important role in investigating climate change, in monitoring biological, biogeochemical, evolutionary, and ecological changes in the sea, ocean, and lake environments, and in helping to control and maintain oil production facilities and harbors using unmanned underwater vehicles (UUVs), submarines, ships, buoys, and divers. However, the present technology of underwater acoustic communication cannot provide the high data rate required to investigate and monitor these environments and facilities. Optical wireless communication has been proposed as the best alternative to meet this challenge. Models are presented for three kinds of optical wireless communication links: (a) a line-of-sight link, (b) a modulating retroreflector link, and (c) a reflective link, all of which can provide the required data rate. We analyze the link performance based on these models. From the analysis, it is clear that as the water absorption increases, the communication performance decreases dramatically for the three link types. However, by using the scattered light it was possible to mitigate this decrease in some cases. It is concluded from the analysis that a high-data-rate underwater optical wireless network is a feasible solution for emerging applications such as UUV-to-UUV links and networks of sensors, and extended ranges in these applications could be achieved by applying a multi-hop concept.

  5. Surface morphology of sound deciduous tooth enamel after application of a photo-absorbing cream and infrared low-level laser irradiation: an in vitro scanning electron microscopy study.

    Science.gov (United States)

    De Sant'Anna, Giselle Rodrigues; Paleari, Giovanna Souza Leão; Duarte, Danilo Antônio; Brugnera, Aldo; Soares, Cristina Pacheco

    2007-12-01

    The purpose of this descriptive scanning electron microscopic study was to characterize surface alterations in deciduous tooth enamel after in vitro infrared diode laser irradiation, using a photo-absorbing agent alone and also combined with fluoride, before and after laser irradiation. Previous investigations have demonstrated increased enamel caries resistance after laser irradiation. Seven extracted or exfoliated primary molar teeth underwent soft tissue débridement and fluoride-free prophylaxis. Buccal surfaces were determined to be caries free by macroscopic examination. Sample groups were divided into: (1) control (no treatment); (2) infrared diode laser irradiation (lambda = 810 nm, 68 nm, 60 mW/mm(2), 30 W) using the photo-absorbing agent alone (IRDL + PA; 500 J/cm(2)); and (3) infrared diode laser irradiation using a photo-absorbing agent combined with 2% fluoride (IRDL + PFA; 500 J/cm(2)). Buccal surfaces were evaluated following standard scanning electron microscopy preparation techniques. Control samples of enamel surfaces were relatively smooth but presented occasional enamel prism ends. There were no areas with cavitations or surface defects. After the IRDL + PA treatment, irradiated surfaces became rough and mildly to moderately irregular with scarce enamel cavitations and without exposure of enamel prism ends. The surfaces had adherent granules and only occasional fine cracks and porosities in surface coatings were noted. After the IRDL + PFA treatment, there was a homogenous confluent surface that masked typical enamel surface markings. The surfaces had well-defined globules resulting from the IRDL + PFA treatment, that were not seen after IRDL + PA treatment. Treatment of deciduous tooth enamel with infrared diode laser irradiation using a photo-absorbing agent and a photo-absorbing agent combined with 2% fluoride created surface coatings that may act as reservoirs for mineral phases during cariogenic activity on enamel, and also provide a

  6. Underwater versus dry irradiation with 60Co, a qualitative analysis

    International Nuclear Information System (INIS)

    Omi, Nelson M.; Rela, Paulo R.

    2007-01-01

    The development of gemstone gamma irradiation devices showed that underwater irradiation leads to better results than the irradiation in dry condition. Many reasons may be shown for that behavior. This work intends to analyze qualitatively two of these reasons. The medium discontinuity between the irradiation source, gemstone, and the air inside the irradiation devices, which is minimized in underwater irradiation, is one of them. The other analyzed hypothesis is the differences between the interactions of source's direct radiation and those from the scattered radiation. The numerical study of these hypothesis, as long as some irradiation tests may be presented in future works. The main conclusion of this work is that the absorbed dose may have different behavior view if the depending on the kind and energy level of the absorbed dose. For example, it is not used to consider what portion of the dose is due to source's direct hit, what part is from ejected electrons with high or low energy and how much high, medium and low energy electro-magnetic quanta hit a portion of mass when determining its radiation dose. To know the total absorbed dose is usually, but not always, enough to explain a material response to radiation. (author)

  7. Underwater cutting techniques developments

    International Nuclear Information System (INIS)

    Bach, F.-W.

    1990-01-01

    The primary circuit structures of different nuclear powerplants are constructed out of stainless steels, ferritic steels, plated ferritic steels and alloys of aluminium. According to the level of the specific radiation of these structures, it is necessary for dismantling to work with remote controlled cutting techniques. The most successful way to protect the working crew against exposure of radiation is to operate underwater in different depths. The following thermal cutting processes are more or less developed to work under water: For ferritic steels only - flame cutting; For ferritic steels, stainless steels, cladded steels and aluminium alloys - oxy-arc-cutting, arc-waterjet-cutting with a consumable electrode, arc-saw-cutting, plasma-arc-cutting and plasma-arc-saw. The flame cutting is a burning process, all the other processes are melt-cutting processes. This paper explains the different techniques, giving a short introduction of the theory, a discussion of the possibilities with the advantages and disadvantages of these processes giving a view into the further research work in this interesting field. (author)

  8. Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions

    Directory of Open Access Journals (Sweden)

    Dalhatu Muhammed

    2018-02-01

    Full Text Available Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal, long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node’s cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted.

  9. Game Theory-Based Cooperation for Underwater Acoustic Sensor Networks: Taxonomy, Review, Research Challenges and Directions.

    Science.gov (United States)

    Muhammed, Dalhatu; Anisi, Mohammad Hossein; Zareei, Mahdi; Vargas-Rosales, Cesar; Khan, Anwar

    2018-02-01

    Exploring and monitoring the underwater world using underwater sensors is drawing a lot of attention these days. In this field cooperation between acoustic sensor nodes has been a critical problem due to the challenging features such as acoustic channel failure (sound signal), long propagation delay of acoustic signal, limited bandwidth and loss of connectivity. There are several proposed methods to improve cooperation between the nodes by incorporating information/game theory in the node's cooperation. However, there is a need to classify the existing works and demonstrate their performance in addressing the cooperation issue. In this paper, we have conducted a review to investigate various factors affecting cooperation in underwater acoustic sensor networks. We study various cooperation techniques used for underwater acoustic sensor networks from different perspectives, with a concentration on communication reliability, energy consumption, and security and present a taxonomy for underwater cooperation. Moreover, we further review how the game theory can be applied to make the nodes cooperate with each other. We further analyze different cooperative game methods, where their performance on different metrics is compared. Finally, open issues and future research direction in underwater acoustic sensor networks are highlighted.

  10. Variation of reverberation time with quantity of absorbers in an ...

    African Journals Online (AJOL)

    An experimental investigation of reverberation of sound at frequencies of 500 and 1000Hz in a room of 35.27m3 has been carried out using B & K Type acoustic instruments. Varied amount of Celotex ceiling board was used as the sound absorber. The result showed that the reverberation time falls progressively with ...

  11. variation of reverberation time with quantity of absorbers in an ...

    African Journals Online (AJOL)

    DJFLEX

    An experimental investigation of reverberation of sound at frequencies of 500 and 1000Hz in a room of. 35.27m3 has been carried out using B & K Type acoustic instruments. Varied amount of Celotex ceiling board was used as the sound absorber. The result showed that the reverberation time falls progressively with ...

  12. Design of Autonomous Underwater Vehicle

    Directory of Open Access Journals (Sweden)

    Tadahiro Hyakudome

    2011-03-01

    Full Text Available There are concerns about the impact that global warming will have on our environment, and which will inevitably result in expanding deserts and rising water levels. While a lot of underwater vehicles are utilized, AUVs (Autonomous Underwater Vehicle were considered and chosen, as the most suitable tool for conduction survey concerning these global environmental problems. AUVs can comprehensive survey because the vehicle does not have to be connected to the support vessel by tether cable. When such underwater vehicles are made, it is necessary to consider about the following things. 1 Seawater and Water Pressure Environment, 2 Sink, 3 There are no Gas or Battery Charge Stations, 4 Global Positioning System cannot use, 5 Radio waves cannot use. In the paper, outline of above and how deal about it are explained.

  13. Bioacoustic Spectral Whistle Sound And Behaviour Of Male Dolphin Bottle Nose ( Tursiops aduncus) At Safari Park Indonesia, Cisarua Bogor

    OpenAIRE

    Muhamad Zainuddin Lubis; Sri Pujiyati; Totok Hestirianoto

    2016-01-01

    Whistle sound is generally used for echolocation purposes, while the sound of the blast-beat and whistles play a major role in internal and inter-group communication.The purpose of this research is to know the power spectral patterns and fluctuations in sound based on frequency and Power Spectral Density (PSD) of the sounds produced by dolphins and observing the position of dolphins , Noisy Time Domain (NTD) and behavior using underwater camera, and also comparing between time and sound spect...

  14. Interpreting underwater acoustic images of the upper ocean boundary layer

    International Nuclear Information System (INIS)

    Ulloa, Marco J

    2007-01-01

    A challenging task in physical studies of the upper ocean using underwater sound is the interpretation of high-resolution acoustic images. This paper covers a number of basic concepts necessary for undergraduate and postgraduate students to identify the most distinctive features of the images, providing a link with the acoustic signatures of physical processes occurring simultaneously beneath the surface of the sea. Sonars are so sensitive that they detected a new acoustic signature at the breaking of surface gravity waves in deep water, which resembles oblique motion-like vortices

  15. Averaging underwater noise levels for environmental assessment of shipping.

    Science.gov (United States)

    Merchant, Nathan D; Blondel, Philippe; Dakin, D Tom; Dorocicz, John

    2012-10-01

    Rising underwater noise levels from shipping have raised concerns regarding chronic impacts to marine fauna. However, there is a lack of consensus over how to average local shipping noise levels for environmental impact assessment. This paper addresses this issue using 110 days of continuous data recorded in the Strait of Georgia, Canada. Probability densities of ~10(7) 1-s samples in selected 1/3 octave bands were approximately stationary across one-month subsamples. Median and mode levels varied with averaging time. Mean sound pressure levels averaged in linear space, though susceptible to strong bias from outliers, are most relevant to cumulative impact assessment metrics.

  16. Bend-absorbing clamp

    Science.gov (United States)

    Abbott, J. R.; Valencia, B., Jr.

    1979-01-01

    Compact, inexpensive clamp for flexible cables or rigid tubes absorbs vibrations and other motion. It accomodates wide range of dimensions, and saves space by eliminating pigtails or bellows commonly used to absorb linear movement or vibrations

  17. Underwater laser imaging system (UWLIS)

    Energy Technology Data Exchange (ETDEWEB)

    DeLong, M. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    Practical limitations with underwater imaging systems area reached when the noise in the back scattered radiation generated in the water between the imaging system and the target obscures the spatial contrast and resolution necessary for target discovery and identification. The advent of high power lasers operating in the blue-green portion of the visible spectrum (oceanic transmission window) has led to improved experimental illumination systems for underwater imaging. Range-gated and synchronously scanned devices take advantage of the unique temporal and spatial coherence properties of laser radiation, respectively, to overcome the deleterious effects of common volume back scatter.

  18. Underwater measurements of muon intensity

    Science.gov (United States)

    Fedorov, V. M.; Pustovetov, V. P.; Trubkin, Y. A.; Kirilenkov, A. V.

    1985-01-01

    Experimental measurements of cosmic ray muon intensity deep underwater aimed at determining a muon absorption curve are of considerable interest, as they allow to reproduce independently the muon energy spectrum at sea level. The comparison of the muon absorption curve in sea water with that in rock makes it possible to determine muon energy losses caused by nuclear interactions. The data available on muon absorption in water and that in rock are not equivalent. Underground measurements are numerous and have been carried out down to the depth of approx. 15km w.e., whereas underwater muon intensity have been measured twice and only down to approx. 3km deep.

  19. Breath sounds

    Science.gov (United States)

    ... described as moist, dry, fine, and coarse. Rhonchi. Sounds that resemble snoring. They occur when air is blocked or air flow becomes rough through the large airways. Stridor. Wheeze-like sound heard when a person breathes. Usually it is ...

  20. Imagining Sound

    DEFF Research Database (Denmark)

    Grimshaw, Mark; Garner, Tom Alexander

    2014-01-01

    We make the case in this essay that sound that is imagined is both a perception and as much a sound as that perceived through external stimulation. To argue this, we look at the evidence from auditory science, neuroscience, and philosophy, briefly present some new conceptual thinking on sound...... that accounts for this view, and then use this to look at what the future might hold in the context of imagining sound and developing technology....

  1. Changes in 63Hz third-octave band sound levels over 42 months recorded at four deep-ocean observatories

    NARCIS (Netherlands)

    Schaar, M. van der; Ainslie, M.A.; Robinson, S.P.; Prior, M.K.; André, M.

    2014-01-01

    The growing scientific and societal concerns about the effects of underwater sound on marine ecosystems have been recently recognised through the introduction of several international initiatives, like the International Quiet Ocean Experiment, aimed at measuring the environmental impact of ocean

  2. An Underwater Color Image Quality Evaluation Metric.

    Science.gov (United States)

    Yang, Miao; Sowmya, Arcot

    2015-12-01

    Quality evaluation of underwater images is a key goal of underwater video image retrieval and intelligent processing. To date, no metric has been proposed for underwater color image quality evaluation (UCIQE). The special absorption and scattering characteristics of the water medium do not allow direct application of natural color image quality metrics especially to different underwater environments. In this paper, subjective testing for underwater image quality has been organized. The statistical distribution of the underwater image pixels in the CIELab color space related to subjective evaluation indicates the sharpness and colorful factors correlate well with subjective image quality perception. Based on these, a new UCIQE metric, which is a linear combination of chroma, saturation, and contrast, is proposed to quantify the non-uniform color cast, blurring, and low-contrast that characterize underwater engineering and monitoring images. Experiments are conducted to illustrate the performance of the proposed UCIQE metric and its capability to measure the underwater image enhancement results. They show that the proposed metric has comparable performance to the leading natural color image quality metrics and the underwater grayscale image quality metrics available in the literature, and can predict with higher accuracy the relative amount of degradation with similar image content in underwater environments. Importantly, UCIQE is a simple and fast solution for real-time underwater video processing. The effectiveness of the presented measure is also demonstrated by subjective evaluation. The results show better correlation between the UCIQE and the subjective mean opinion score.

  3. An Autonomous Underwater Recorder Based on a Single Board Computer

    Science.gov (United States)

    Caldas-Morgan, Manuel; Alvarez-Rosario, Alexander; Rodrigues Padovese, Linilson

    2015-01-01

    As industrial activities continue to grow on the Brazilian coast, underwater sound measurements are becoming of great scientific importance as they are essential to evaluate the impact of these activities on local ecosystems. In this context, the use of commercial underwater recorders is not always the most feasible alternative, due to their high cost and lack of flexibility. Design and construction of more affordable alternatives from scratch can become complex because it requires profound knowledge in areas such as electronics and low-level programming. With the aim of providing a solution; a well succeeded model of a highly flexible, low-cost alternative to commercial recorders was built based on a Raspberry Pi single board computer. A properly working prototype was assembled and it demonstrated adequate performance levels in all tested situations. The prototype was equipped with a power management module which was thoroughly evaluated. It is estimated that it will allow for great battery savings on long-term scheduled recordings. The underwater recording device was successfully deployed at selected locations along the Brazilian coast, where it adequately recorded animal and manmade acoustic events, among others. Although power consumption may not be as efficient as that of commercial and/or micro-processed solutions, the advantage offered by the proposed device is its high customizability, lower development time and inherently, its cost. PMID:26076479

  4. An Autonomous Underwater Recorder Based on a Single Board Computer.

    Science.gov (United States)

    Caldas-Morgan, Manuel; Alvarez-Rosario, Alexander; Rodrigues Padovese, Linilson

    2015-01-01

    As industrial activities continue to grow on the Brazilian coast, underwater sound measurements are becoming of great scientific importance as they are essential to evaluate the impact of these activities on local ecosystems. In this context, the use of commercial underwater recorders is not always the most feasible alternative, due to their high cost and lack of flexibility. Design and construction of more affordable alternatives from scratch can become complex because it requires profound knowledge in areas such as electronics and low-level programming. With the aim of providing a solution; a well succeeded model of a highly flexible, low-cost alternative to commercial recorders was built based on a Raspberry Pi single board computer. A properly working prototype was assembled and it demonstrated adequate performance levels in all tested situations. The prototype was equipped with a power management module which was thoroughly evaluated. It is estimated that it will allow for great battery savings on long-term scheduled recordings. The underwater recording device was successfully deployed at selected locations along the Brazilian coast, where it adequately recorded animal and manmade acoustic events, among others. Although power consumption may not be as efficient as that of commercial and/or micro-processed solutions, the advantage offered by the proposed device is its high customizability, lower development time and inherently, its cost.

  5. Recoverable neutron absorbers

    International Nuclear Information System (INIS)

    Keay, R.T.; Williams, J.A.

    1982-01-01

    In the reprocessing of irradiated nuclear fuel elements the nuclear fuel material is separated from the material which forms the remainder of the elements by dissolving the nuclear fuel material in nitric acid. Neutron absorbers are added to control criticality. The neutron absorbers comprise pellets each having a core of neutron absorbing material encased in a sheath of a material which is resistant to attack by acid, the core or sheath being magnetic. The sheath protects the core of neutron absorbing material from attack by the acid and the magnetic content of the core or sheath enables the absorbers to be recovered for reuse by magnetic separation techniques. (author)

  6. The Flexible Bass Absorber

    DEFF Research Database (Denmark)

    Adelman-Larsen, Niels Werner; Thompson, Eric Robert; Gade, Anders Christian

    2007-01-01

    Multi-purpose concert halls face a dilemma. They host different performance types that require significantly different acoustic conditions in order to provide the best sound quality to both the performers, sound engineers and the audience. Pop and rock music often contains high levels of bass sound...

  7. Measuring sound absorption using local field assumptions

    NARCIS (Netherlands)

    Kuipers, E.R.

    2013-01-01

    To more effectively apply acoustically absorbing materials, it is desirable to measure angle-dependent sound absorption coefficients, preferably in situ. Existing measurement methods are based on an overall model of the acoustic field in front of the absorber, and are therefore sensitive to

  8. Fluid Sounds

    DEFF Research Database (Denmark)

    and in architectural design. Aesthetics, psychoacoustics, perception, and cognition are all present in this expanding field embracing such categories as soundscape composition, sound art, sonic art, sound design, sound studies and auditory culture. Of greatest significance to the overall field is the investigation...... of sound, site and the social, and how the spatial, the visual, and the bodily interact in sonic environments, how they are constructed and how they are entangled in other practices. With the Seismograf special issue Fluid Sounds, we bring this knowledge into the dissemination of audio research itself...

  9. Underwater nuclear power plant structure

    International Nuclear Information System (INIS)

    Severs, S.; Toll, H.V.

    1982-01-01

    A structure for an underwater nuclear power generating plant comprising a triangular platform formed of tubular leg and truss members upon which are attached one or more large spherical pressure vessels and one or more small cylindrical auxiliary pressure vessels. (author)

  10. Underwater Robots Surface in Utah

    Science.gov (United States)

    Hurd, Randy C.; Hacking, Kip S.; Damarjian, Jennifer L.; Wright, Geoffrey A.; Truscott, Tadd

    2015-01-01

    Underwater robots (or ROVs: Remotely Operated Vehicles as they are typically called in industry) have recently become a very popular instructional STEM activity. Nationally, ROVs have been used in science and technology classrooms for several years in cities such as Seattle, San Diego, Virginia Beach, and other coastal areas. In the past two…

  11. A study on practical use of underwater abrasive water jet cutting

    Science.gov (United States)

    Yamaguchi, Hitoshi; Demura, Kenji

    1993-09-01

    The practicality of underwater abrasive water jet cutting technology was studied in experiments. A study of abrasives in slurried form showed that optimum polymer concentration can be selected to suit underwater conditions. For the long-distance transport of slurry from the ocean surface to the ocean floor, a direct supply system by hose proved to be practical. This system takes advantage of the insolubility of the slurry in water due to a difference in specific gravity. For cutting thick steel plate at great ocean depths, a simulation with a pressurized container revealed the requirements for actual cutting. Confirmation of remote cutting operations will become the most important technology in field applications. Underwater sound vibration characteristics were found to change significantly in direct response to modifications in cutting conditions. This will be important basic data to develop an effective sensoring method.

  12. Analysis of humpback whale sounds in shallow waters of the ...

    Indian Academy of Sciences (India)

    Acoustic parameters; breeding habitat; humpback whale; phrases; sound units; thematic structure. Published online: 27 April 2015 ... ed against a standard sensor at the underwater Acoustic Test. Facility of NIOT, which is the only ..... Landing Marine Laboratories, California State University. Papastavrou V 1995 Soviets ...

  13. Underwater radiated noise from modern commercial ships.

    Science.gov (United States)

    McKenna, Megan F; Ross, Donald; Wiggins, Sean M; Hildebrand, John A

    2012-01-01

    Underwater radiated noise measurements for seven types of modern commercial ships during normal operating conditions are presented. Calibrated acoustic data (autonomous seafloor-mounted acoustic recorder were combined with ship passage information from the Automatic Identification System. This approach allowed for detailed measurements (i.e., source level, sound exposure level, and transmission range) on ships of opportunity. A key result was different acoustic levels and spectral shapes observed from different ship-types. A 54 kGT container ship had the highest broadband source level at 188 dB re 1 μPa@1m; a 26 kGT chemical tanker had the lowest at 177 dB re 1 μPa@1m. Bulk carriers had higher source levels near 100 Hz, while container ship and tanker noise was predominantly below 40 Hz. Simple models to predict source levels of modern merchant ships as a group from particular ship characteristics (e.g., length, gross tonnage, and speed) were not possible given individual ship-type differences. Furthermore, ship noise was observed to radiate asymmetrically. Stern aspect noise levels are 5 to 10 dB higher than bow aspect noise levels. Collectively, these results emphasize the importance of including modern ship-types in quantifying shipping noise for predictive models of global, regional, and local marine environments. © 2012 Acoustical Society of America.

  14. Sensitivity of a tucuxi (Sotalia fluviatilis guianensis) to airborne sound

    Science.gov (United States)

    Liebschner, Alexander; Hanke, Wolf; Miersch, Lars; Dehnhardt, Guido; Sauerland, Matthias

    2005-01-01

    Auditory systems of cetaceans are considered highly specialized for underwater sound processing, whereas the extent of their hearing capacity in air is still a point of issue. In this study, the sensitivity to airborne sound in a male tucuxi (Sotalia fluviatilis guianensis) was tested by means of a go/no go response paradigm. Auditory thresholds were obtained from 2 to 31.5 kHz. Compared to the hearing thresholds of other dolphins as well as of amphibian mammals, the sensitivity to airborne sound of the test subject is low from 2 to 8 kHz, with the highest threshold at 4 kHz. Thresholds at 16 and 31.5 kHz reveal a sharp increase in hearing sensitivity. Thus, although not obtained in this study, the upper aerial hearing limit is in the ultrasonic range. A comparison of the present data with the underwater audiogram of the same test subject referred to sound intensity indicates that the sensitivity of Sotalia to underwater sound is generally better than to airborne sound. .

  15. Underwater noise from a wave energy converter

    DEFF Research Database (Denmark)

    Tougaard, Jakob

    of the absorber type. During recordings the converter was operating close to maximum power output (nominal capacity of 110 kW). During operation the independently operating absorbers float semi-submerged in the water and wave-generated up-and-down motion is converted into hydraulic pressure by means of pistons...... connected to the arms of the absorbers. The hydraulic pressure then in turn drives the generator. A 57 minute sequence of noise from the converter was recorded by a Loggerhead datalogger deployed in 7 m deep water 25 m from the converter. This sequence contained recordings of ambient noise, the converter...... in full operation and start and stop of the converter. Median broad band (10 Hz – 20 kHz) sound pressure level (Leq) was 123 dB re. 1 Pa, irrespective of status of the wave energy converter (stopped, running or starting/stopping). The most pronounced peak in the third-octave spectrum was in the 160 Hz...

  16. Unsound Sound

    DEFF Research Database (Denmark)

    Knakkergaard, Martin

    2016-01-01

    This article discusses the change in premise that digitally produced sound brings about and how digital technologies more generally have changed our relationship to the musical artifact, not simply in degree but in kind. It demonstrates how our acoustical conceptions are thoroughly challenged...... by the digital production of sound and, by questioning the ontological basis for digital sound, turns our understanding of the core term substance upside down....

  17. Sound absorption study of raw and expanded particulate vermiculites

    Science.gov (United States)

    Vašina, Martin; Plachá, Daniela; Mikeska, Marcel; Hružík, Lumír; Martynková, Gražyna Simha

    2016-12-01

    Expanded and raw vermiculite minerals were studied for their ability to absorb sound. Phase and structural characterization of the investigated vermiculites was found similar for both types, while morphology and surface properties vary. Sound waves reflect in wedge-like structure and get minimized, and later are absorbed totally. We found that thanks to porous character of expanded vermiculite the principle of absorption of sound into layered vermiculite morphology is analogous to principle of sound minimization in "anechoic chambers." It was found in this study that the best sound damping properties of the investigated vermiculites were in general obtained at higher powder bed heights and higher excitation frequencies.

  18. The influence of environmental parameters on the optimal frequency in a shallow underwater acoustic channel

    Science.gov (United States)

    Zarnescu, George

    2015-02-01

    In a shallow underwater acoustic channel the delayed replicas of a transmitted signal are mainly due to the interactions with the sea surface and the bottom layer. If a specific underwater region on the globe is considered, for which the sedimentary layer structure is constant across the transmission distance, then the variability of the amplitude-delay profile is determined by daily and seasonal changes of the sound speed profile (SSP) and by weather changes, such as variations of the wind speed. Such a parameter will influence the attenuation at the surface, the noise level and the profile of the sea surface. The temporal variation of the impulse response in a shallow underwater acoustic channel determines the variability of the optimal transmission frequency. If the ways in which the optimal frequency changes can be predicted, then an adaptive analog transceiver can be easily designed for an underwater acoustic modem or it can be found when a communication link has high throughput. In this article it will be highlighted the way in which the amplitude-delay profile is affected by the sound speed profile, wind speed and channel depth and also will be emphasized the changes of the optimal transmission frequency in a configuration, where the transmitter and receiver are placed on the seafloor and the bathymetry profile will be considered flat, having a given composition.

  19. Network Computing for Distributed Underwater Acoustic Sensors

    Science.gov (United States)

    2014-03-31

    Physical layer in UASNs Our main investigations are about underwater communications using acoustic waves. Elec- tromagnetic and optical waves do not...Shengli, Z., and Jun-Hong, C. (2008), Prospects and problems of wireless communication for underwater sensor networks, Wirel. Commun . Mob. Comput., 8(8... Wireless Communications , 9(9), 2934–2944. [21] Pompili, D. and Akyildiz, I. (2010), A multimedia cross-layer protocol for underwater acoustic sensor networks

  20. Cooperative OFDM underwater acoustic communications

    CERN Document Server

    Cheng, Xilin; Cheng, Xiang

    2016-01-01

    Following underwater acoustic channel modeling, this book investigates the relationship between coherence time and transmission distances. It considers the power allocation issues of two typical transmission scenarios, namely short-range transmission and medium-long range transmission. For the former scenario, an adaptive system is developed based on instantaneous channel state information. The primary focus is on cooperative dual-hop orthogonal frequency division multiplexing (OFDM). This book includes the decomposed fountain codes designed to enable reliable communications with higher energy efficiency. It covers the Doppler Effect, which improves packet transmission reliability for effective low-complexity mirror-mapping-based intercarrier interference cancellation schemes capable of suppressing the intercarrier interference power level. Designed for professionals and researchers in the field of underwater acoustic communications, this book is also suitable for advanced-level students in electrical enginee...

  1. International Conference on Underwater Environment

    CERN Document Server

    Jaulin, Luc; Creuze, Vincent; Debese, Nathalie; Quidu, Isabelle; Clement, Benoît; Billon-Coat, Annick

    2016-01-01

    This volume constitutes the results of the International Conference on Underwater Environment, MOQESM’14, held at “Le Quartz” Conference Center in Brest, France, on October 14-15, 2014, within the framework of the 9th Sea Tech Week, International Marine Science and Technology Event. The objective of MOQESM'14 was to bring together researchers from both academia and industry, interested in marine robotics and hydrography with application to the coastal environment mapping and underwater infrastructures surveys. The common thread of the conference is the combination of technical control, perception, and localization, typically used in robotics, with the methods of mapping and bathymetry. The papers presented in this book focus on two main topics. Firstly, coastal and infrastructure mapping is addressed, focusing not only on hydrographic systems, but also on positioning systems, bathymetry, and remote sensing. The proposed methods rely on acoustic sensors such as side scan sonars, multibeam echo sounders, ...

  2. Sound generator

    NARCIS (Netherlands)

    Berkhoff, Arthur P.

    2008-01-01

    A sound generator, particularly a loudspeaker, configured to emit sound, comprising a rigid element (2) enclosing a plurality of air compartments (3), wherein the rigid element (2) has a back side (B) comprising apertures (4), and a front side (F) that is closed, wherein the generator is provided

  3. Sound generator

    NARCIS (Netherlands)

    Berkhoff, Arthur P.

    2010-01-01

    A sound generator, particularly a loudspeaker, configured to emit sound, comprising a rigid element (2) enclosing a plurality of air compartments (3), wherein the rigid element (2) has a back side (B) comprising apertures (4), and a front side (F) that is closed, wherein the generator is provided

  4. Sound generator

    NARCIS (Netherlands)

    Berkhoff, Arthur P.

    2007-01-01

    A sound generator, particularly a loudspeaker, configured to emit sound, comprising a rigid element (2) enclosing a plurality of air compartments (3), wherein the rigid element (2) has a back side (B) comprising apertures (4), and a front side (F) that is closed, wherein the generator is provided

  5. Sound knowledge

    DEFF Research Database (Denmark)

    Kauffmann, Lene Teglhus

    of the research is to investigate what is considered to ‘work as evidence’ in health promotion and how the ‘evidence discourse’ influences social practices in policymaking and in research. From investigating knowledge practices in the field of health promotion, I develop the concept of sound knowledge...... making, which I call ‘sound knowledge’. Sound knowledge is an approach to knowledge that takes the reflexive considerations of actors in policymaking processes as well as in research about what knowledge is into account. Seeing knowledge as sound makes connections between different ideas, concepts...... and ideologies explicit. Furthermore, in relation to an anthropology of knowledge, sound knowledge also offers a reconsideration of the way anthropologists study knowledge, as it specifies that studying knowledge for anthropologists means studying what people consider as knowledge, in what circumstances...

  6. Underwater Coatings for Contamination Control

    International Nuclear Information System (INIS)

    Julia L. Tripp; Kip Archibald; Ann-Marie Phillips; Joseph Campbell

    2004-01-01

    The Idaho National Engineering and Environmental Laboratory (INEEL) is deactivating several fuel storage basins. Airborne contamination is a concern when the sides of the basins are exposed and allowed to dry during water removal. One way of controlling this airborne contamination is to fix the contamination in place while the pool walls are still submerged. There are many underwater coatings available on the market that are used in marine, naval and other applications. A series of tests were run to determine whether the candidate underwater fixatives are easily applied and adhere well to the substrates (pool wall materials) found in INEEL fuel pools. The four pools considered included (1) Test Area North (TAN-607) with epoxy painted concrete walls; (2) Idaho Nuclear Technology and Engineering Center (INTEC) (CPP-603) with bare concrete walls; (3) Materials Test Reactor (MTR) Canal with stainless steel lined concrete walls; and (4) Power Burst Facility (PBF-620) with stainless steel lined concrete walls on the bottom and epoxy painted carbon steel lined walls on the upper portions. Therefore, the four materials chosen for testing included bare concrete, epoxy painted concrete, epoxy painted carbon steel, and stainless steel. The typical water temperature of the pools varies from 55 F to 80 F dependent on the pool and the season. These tests were done at room temperature. The following criteria were used during this evaluation. The underwater coating must: (1) Be easy to apply; (2) Adhere well to the four surfaces of interest; (3) Not change or have a negative impact on water chemistry or clarity; (4) Not be hazardous in final applied form; and (5) Be proven in other underwater applications. In addition, it is desirable for the coating to have a high pigment or high cross-link density to prevent radiation from penetrating. This paper will detail the testing completed and the test results. A proprietary two-part, underwater epoxy owned by S. G. Pinney and Associates

  7. Modelling techniques for underwater noise generated by tidal turbines in shallow water

    OpenAIRE

    Lloyd, Thomas P.; Turnock, Stephen R.; Humphrey, Victor F.

    2011-01-01

    The modelling of underwater noise sources and their potential impact on the marine environment is considered, focusing on tidal turbines in shallow water. The requirement for device noise prediction as part of environmental impact assessment is outlined and the limited amount of measurement data and modelling research identified. Following the identification of potential noise sources, the dominant flowgenerated sources are modelled using empirical techniques. The predicted sound pressure lev...

  8. Array Receivers and Sound Sources for Three Dimensional Shallow Water Acoustic Field Experiments

    Science.gov (United States)

    2016-12-06

    great success. Our acoustics research groups, the Ocean Acoustics and Signals Laboratory and the Acoustic Communications Group, in the Applied Ocean...field efforts in shallow-water acoustics and underwater acoustic communications. We have plans to upgrade our existing hydrophone arrays and sound...Hydrophone Receiver Unit) arrays. The immedate objective was to improve our fieldwork capibility and to enhance the quality of our underwater acoustic

  9. Sound exposure changes European seabass behaviour in a large outdoor floating pen: Effects of temporal structure and a ramp-up procedure

    NARCIS (Netherlands)

    Neo, Y.Y.; Hubert, J.; Bolle, L.J.; Winter, Hendrik V.; Cate, ten C.; Slabbekoorn, H.

    2016-01-01

    Underwater sound from human activities may affect fish behaviour negatively and threaten the stability of fish stocks. However, some fundamental understanding is still lacking for adequate impact assessments and potential mitigation strategies. For example, little is known about the potential

  10. Novel underwater soundscape: acoustic repertoire of plainfin midshipman fish.

    Science.gov (United States)

    McIver, Eileen L; Marchaterre, Margaret A; Rice, Aaron N; Bass, Andrew H

    2014-07-01

    Toadfishes are among the best-known groups of sound-producing (vocal) fishes and include species commonly known as toadfish and midshipman. Although midshipman have been the subject of extensive investigation of the neural mechanisms of vocalization, this is the first comprehensive, quantitative analysis of the spectro-temporal characters of their acoustic signals and one of the few for fishes in general. Field recordings of territorial, nest-guarding male midshipman during the breeding season identified a diverse vocal repertoire composed of three basic sound types that varied widely in duration, harmonic structure and degree of amplitude modulation (AM): 'hum', 'grunt' and 'growl'. Hum duration varied nearly 1000-fold, lasting for minutes at a time, with stable harmonic stacks and little envelope modulation throughout the sound. By contrast, grunts were brief, ~30-140 ms, broadband signals produced both in isolation and repetitively as a train of up to 200 at intervals of ~0.5-1.0 s. Growls were also produced alone or repetitively, but at variable intervals of the order of seconds with durations between those of grunts and hums, ranging 60-fold from ~200 ms to 12 s. Growls exhibited prominent harmonics with sudden shifts in pulse repetition rate and highly variable AM patterns, unlike the nearly constant AM of grunt trains and flat envelope of hums. Behavioral and neurophysiological studies support the hypothesis that each sound type's unique acoustic signature contributes to signal recognition mechanisms. Nocturnal production of these sounds against a background chorus dominated constantly for hours by a single sound type, the multi-harmonic hum, reveals a novel underwater soundscape for fish. © 2014. Published by The Company of Biologists Ltd.

  11. Sound Zones

    DEFF Research Database (Denmark)

    Møller, Martin Bo; Olsen, Martin

    2017-01-01

    Sound zones, i.e. spatially confined regions of individual audio content, can be created by appropriate filtering of the desired audio signals reproduced by an array of loudspeakers. The challenge of designing filters for sound zones is twofold: First, the filtered responses should generate...... an acoustic separation between the control regions. Secondly, the pre- and post-ringing as well as spectral deterioration introduced by the filters should be minimized. The tradeoff between acoustic separation and filter ringing is the focus of this paper. A weighted L2-norm penalty is introduced in the sound...

  12. Metasurface for Water-to-Air Sound Transmission

    Science.gov (United States)

    Bok, Eun; Park, Jong Jin; Choi, Haejin; Han, Chung Kyu; Wright, Oliver B.; Lee, Sam H.

    2018-01-01

    Effective transmission of sound from water to air is crucial for the enhancement of the detection sensitivity of underwater sound. However, only 0.1% of the acoustic energy is naturally transmitted at such a boundary. At audio frequencies, quarter-wave plates or multilayered antireflection coatings are too bulky for practical use for such enhancement. Here we present an acoustic metasurface of a thickness of only ˜λ /100 , where λ is the wavelength in air, consisting of an array of meta-atoms that each contain a set of membranes and an air-filled cavity. We experimentally demonstrate that such a meta-atom increases the transmission of sound at ˜700 Hz by 2 orders of magnitude, allowing about 30% of the incident acoustic power from water to be transmitted into air. Applications include underwater sonic sensing and communication.

  13. Sound absorption coefficient of coal bottom ash concrete for railway application

    Science.gov (United States)

    Ramzi Hannan, N. I. R.; Shahidan, S.; Maarof, Z.; Ali, N.; Abdullah, S. R.; Ibrahim, M. H. Wan

    2017-11-01

    A porous concrete able to reduce the sound wave that pass through it. When a sound waves strike a material, a portion of the sound energy was reflected back and another portion of the sound energy was absorbed by the material while the rest was transmitted. The larger portion of the sound wave being absorbed, the lower the noise level able to be lowered. This study is to investigate the sound absorption coefficient of coal bottom ash (CBA) concrete compared to the sound absorption coefficient of normal concrete by carried out the impedance tube test. Hence, this paper presents the result of the impedance tube test of the CBA concrete and normal concrete.

  14. Absorber manufacturing made easy

    Energy Technology Data Exchange (ETDEWEB)

    Berner, Joachim

    2010-07-01

    Whether by means of a laser source or an ultrasound head - automation technology is making progress in the solar thermal sector. S and WE presents news developments in welding technology in absorber manufacture. (orig.)

  15. PWR burnable absorber evaluation

    International Nuclear Information System (INIS)

    Cacciapouti, R.J.; Weader, R.J.; Malone, J.P.

    1995-01-01

    The purpose of the study was to evaluate the relative neurotic efficiency and fuel cycle cost benefits of PWR burnable absorbers. Establishment of reference low-leakage equilibrium in-core fuel management plans for 12-, 18- and 24-month cycles. Review of the fuel management impact of the integral fuel burnable absorber (IFBA), erbium and gadolinium. Calculation of the U 3 O 8 , UF 6 , SWU, fuel fabrication, and burnable absorber requirements for the defined fuel management plans. Estimation of fuel cycle costs of each fuel management plan at spot market and long-term market fuel prices. Estimation of the comparative savings of the different burnable absorbers in dollar equivalent per kgU of fabricated fuel. (author)

  16. TOMS Absorbing Aerosol Index

    Data.gov (United States)

    Washington University St Louis — TOMS_AI_G is an aerosol related dataset derived from the Total Ozone Monitoring Satellite (TOMS) Sensor. The TOMS aerosol index arises from absorbing aerosols such...

  17. Sound intensity

    DEFF Research Database (Denmark)

    Crocker, Malcolm J.; Jacobsen, Finn

    1998-01-01

    This chapter is an overview, intended for readers with no special knowledge about this particular topic. The chapter deals with all aspects of sound intensity and its measurement from the fundamental theoretical background to practical applications of the measurement technique.......This chapter is an overview, intended for readers with no special knowledge about this particular topic. The chapter deals with all aspects of sound intensity and its measurement from the fundamental theoretical background to practical applications of the measurement technique....

  18. Sound Intensity

    DEFF Research Database (Denmark)

    Crocker, M.J.; Jacobsen, Finn

    1997-01-01

    This chapter is an overview, intended for readers with no special knowledge about this particular topic. The chapter deals with all aspects of sound intensity and its measurement from the fundamental theoretical background to practical applications of the measurement technique.......This chapter is an overview, intended for readers with no special knowledge about this particular topic. The chapter deals with all aspects of sound intensity and its measurement from the fundamental theoretical background to practical applications of the measurement technique....

  19. A variable passive low-frequency absorber

    Science.gov (United States)

    Larsen, Niels Werner; Thompson, Eric R.; Gade, Anders Christian

    2005-04-01

    Multi-purpose concert halls face a dilemma. They can host classical music concerts, rock concerts and spoken word performances in a matter of a short period. These different performance types require significantly different acoustic conditions in order to provide the best sound quality to both the performers and the audience. A recommended reverberation time for classical music may be in the range of 1.5-2 s for empty halls, where rock music sounds best with a reverberation time around 0.8-1 s. Modern rhythmic music often contains high levels of sound energy in the low frequency bands but still requires a high definition for good sound quality. Ideally, the absorption of the hall should be adjustable in all frequency bands in order to provide good sound quality for all types of performances. The mid and high frequency absorption is easily regulated, but adjusting the low-frequency absorption has typically been too expensive or requires too much space to be practical for multi-purpose halls. Measurements were made on a variable low-frequency absorber to develop a practical solution to the dilemma. The paper will present the results of the measurements as well as a possible design.

  20. Compact Surface Plasmon Resonance Sensor for Underwater Chemical Sensing Robot

    Directory of Open Access Journals (Sweden)

    Yuichi Minagawa

    2017-01-01

    Full Text Available This paper reports on the development of compact surface plasmon resonance (SPR sensors for mobile robot olfaction. Underwater robots benefit from olfactory sensing capabilities in various tasks including the search for unexploded ordnance and undersea wreckage. Although the SPR-based chemical sensor is a promising sensing platform, the cumbersome optical setup has been limiting its use on mobile robots. The proposed sensor employs a periodic metal structure formed on a self-assembled layer of polystyrene particles of 200 nm in diameter. With the grating of this size, SPR can be excited even with a simple LED light source. The change in the absorbance is simply measured using a photodiode. Demonstration of the proposed SPR sensor is provided by mounting the sensors on an underwater crayfish robot that autonomously searches for a chemical source. The fabricated sensor shows linear response to ascorbic acid for a concentration range from 20 to 80 mM. Responses of the bare and thiol-coated gold nanostructure to different chemical substances are presented to show the change in the selectivity of the sensor by the coating. Discussions are made on the importance of sample collection for the sensor to attain sensitive chemical detection on a mobile robot.

  1. Synchronous and Rhythmic Vocalizations and Correlated Underwater Behavior of Free-ranging Atlantic Spotted Dolphins (Stenella frontalis and Bottlenose Dolphins (Tursiops truncatus in the Bahamas

    Directory of Open Access Journals (Sweden)

    Denise L. Herzing

    2015-02-01

    Full Text Available Since 1985 a resident community of Atlantic spotted dolphins (Stenella frontalis, and bottlenose dolphins (Tursiops truncatus, have been studied underwater in the Bahamas. Over 200 individuals of both species have been identified and observed over the years. Basic correlations with sound patterns and behavior such as whistles during contact/reunions and squawks during aggression have been reported. This paper describes a small subset of their vocal repertoire that involves synchronous/rhythmic sound production. Dolphin behavior was recorded underwater using underwater video cameras with hydrophone input. Vocalizations were correlated with basic underwater behavioral activity and analyzed using Raven 1.3. Spotted dolphins were observed using two types of synchronized vocalizations including synchronized squawks (burst pulsed vocalizations and screams- (overlapping FM whistles during intraspecific and interspecific aggression. Bottlenose dolphins used three types of synchronized vocalizations; whistles/buzz bouts, bray/buzz bouts, and buzz bouts during intraspecific aggression. Body postures were synchronous with physical movements and often mirrored the rhythm of the vocalizations. The intervals between highly synchronized vocalizations had small variance and created a rhythmic quality and cadence to the acoustic sequences. Three types of vocalizations had similar ratios of sound duration to the spacing between sounds (Screams, whistle/buzz bouts, and bray/buzz bouts. Temporal aspects of sequences of sound and postures may be important aspects of individual and group coordination and behavior in delphinids.

  2. Underwater inspection by immersion phased array UT technique

    International Nuclear Information System (INIS)

    Hirasawa, Taiji

    2017-01-01

    In the inspection during the service period of a nuclear power plant, ultrasonic flaw detection test (UT) is performed as a volume test to confirm the soundness of the equipment and structure. Phased array UT technology has been applied as a technique to measure with high accuracy the crack depth generated in stainless steel or Ni based alloy welds. This paper picked up main scanning methods based on ultrasonic beam control in phased array UT, as well as items to consider when carrying out underwater UT inspection of reactor internal structure, and described the concept of selection method of flaw detection method. As the example of underwater UT inspection, this paper introduced application examples for actual equipment and test body, in the defect depth measurement of water immersion phased array UT, by choosing reactor internal structures etc. of a BWR plant. The core shroud, core spray piping, jet pump, CRD housing, and shroud support of BWR plant that are introduced here are subject to individual inspection under maintenance standards and are extremely important equipment. (A.O.)

  3. Underwater noise pollution in a coastal tropical environment.

    Science.gov (United States)

    Bittencourt, L; Carvalho, R R; Lailson-Brito, J; Azevedo, A F

    2014-06-15

    Underwater noise pollution has become a major concern in marine habitats. Guanabara Bay, southeastern Brazil, is an impacted area of economic importance with constant vessel traffic. One hundred acoustic recording sessions took place over ten locations. Sound sources operating within 1 km radius of each location were quantified during recordings. The highest mean sound pressure level near the surface was 111.56±9.0 dB re 1 μPa at the frequency band of 187 Hz. Above 15 kHz, the highest mean sound pressure level was 76.21±8.3 dB re 1 μPa at the frequency 15.89 kHz. Noise levels correlated with number of operating vessels and vessel traffic composition influenced noise profiles. Shipping locations had the highest noise levels, while small vessels locations had the lowest noise levels. Guanabara Bay showed noise pollution similar to that of other impacted coastal regions, which is related to shipping and vessel traffic. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Model based image restoration for underwater images

    Science.gov (United States)

    Stephan, Thomas; Frühberger, Peter; Werling, Stefan; Heizmann, Michael

    2013-04-01

    The inspection of offshore parks, dam walls and other infrastructure under water is expensive and time consuming, because such constructions must be inspected manually by divers. Underwater buildings have to be examined visually to find small cracks, spallings or other deficiencies. Automation of underwater inspection depends on established water-proved imaging systems. Most underwater imaging systems are based on acoustic sensors (sonar). The disadvantage of such an acoustic system is the loss of the complete visual impression. All information embedded in texture and surface reflectance gets lost. Therefore acoustic sensors are mostly insufficient for these kind of visual inspection tasks. Imaging systems based on optical sensors feature an enormous potential for underwater applications. The bandwidth from visual imaging systems reach from inspection of underwater buildings via marine biological applications through to exploration of the seafloor. The reason for the lack of established optical systems for underwater inspection tasks lies in technical difficulties of underwater image acquisition and processing. Lightening, highly degraded images make a computational postprocessing absolutely essential.

  5. Active room compensation for sound reinforcement using sound field separation techniques

    DEFF Research Database (Denmark)

    Heuchel, Franz Maria; Fernandez Grande, Efren; Agerkvist, Finn T.

    2018-01-01

    with the three sound separation techniques. Resonances in the entire room are reduced, although the microphone array and secondary sources are confined to a small region close to the reflecting wall. Unlike previous control methods based on the creation of a plane wave sound field, the investigated method works......This work investigates how the sound field created by a sound reinforcement system can be controlled at low frequencies. An indoor control method is proposed which actively absorbs the sound incident on a reflecting boundary using an array of secondary sources. The sound field is separated...... into incident and reflected components by a microphone array close to the secondary sources, enabling the minimization of reflected components by means of optimal signals for the secondary sources. The method is purely feed-forward and assumes constant room conditions. Three different sound field separation...

  6. Neutron absorbing article

    International Nuclear Information System (INIS)

    Naum, R.G.; Owens, D.P.; Dooher, G.I.

    1979-01-01

    A neutron absorbing article, in flat plate form and suitable for use in a storage rack for spent fuel, includes boron carbide particles, diluent particles and a solid, irreversibly cured phenolic polymer cured to a continuous matrix binding the boron carbide and diluent particles. The total conent of boron carbide and diluent particles is a major proportion of the article and the content of cured phenolic polymer present is a minor proportion. By regulation of the ratio of boron carbide particles to diluent particles, normally within the range of 1:9 and 9:1 and preferably within the range of 1:5 to 5:1, the neutron absorbing activity of the product may be controlled, which facilitates the manufacture of articles of particular absorbing activities best suitable for specific applications

  7. Sound beam manipulation based on temperature gradients

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Feng [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); School of Physics & Electronic Engineering, Changshu Institute of Technology, Changshu 215500 (China); Quan, Li; Liu, Xiaozhou, E-mail: xzliu@nju.edu.cn; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-10-28

    Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking.

  8. Sound beam manipulation based on temperature gradients

    International Nuclear Information System (INIS)

    Qian, Feng; Quan, Li; Liu, Xiaozhou; Gong, Xiufen

    2015-01-01

    Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking

  9. Sound settlements

    DEFF Research Database (Denmark)

    Duelund Mortensen, Peder

    2013-01-01

    Præsentation af projektresultater fra Interreg forskningen Sound Settlements om udvikling af bæredygtighed i det almene boligbyggerier i København, Malmø, Helsingborg og Lund samt europæiske eksempler på best practice......Præsentation af projektresultater fra Interreg forskningen Sound Settlements om udvikling af bæredygtighed i det almene boligbyggerier i København, Malmø, Helsingborg og Lund samt europæiske eksempler på best practice...

  10. Sound Settlements

    DEFF Research Database (Denmark)

    Mortensen, Peder Duelund; Hornyanszky, Elisabeth Dalholm; Larsen, Jacob Norvig

    2013-01-01

    Præsentation af projektresultater fra Interreg forskningen Sound Settlements om udvikling af bæredygtighed i det almene boligbyggerier i København, Malmø, Helsingborg og Lund samt europæiske eksempler på best practice......Præsentation af projektresultater fra Interreg forskningen Sound Settlements om udvikling af bæredygtighed i det almene boligbyggerier i København, Malmø, Helsingborg og Lund samt europæiske eksempler på best practice...

  11. A new technique for robot vision in autonomous underwater vehicles using the color shift in underwater imaging

    Science.gov (United States)

    2017-06-01

    FOR ROBOT VISION IN AUTONOMOUS UNDERWATER VEHICLES USING THE COLOR SHIFT IN UNDERWATER IMAGING by Jake A. Jones June 2017 Thesis Advisor... VEHICLES USING THE COLOR SHIFT IN UNDERWATER IMAGING 5. FUNDING NUMBERS 6. AUTHOR(S) Jake A. Jones 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS...underwater vehicles (AUVs), robot vision, autonomy, visual odometry, underwater color shift, optical properties of water 15. NUMBER OF PAGES 75 16

  12. Microstructural characterizations and mechanical properties in underwater friction stir welding of aluminum and magnesium dissimilar alloys

    International Nuclear Information System (INIS)

    Zhao, Yong; Lu, Zhengping; Yan, Keng; Huang, Linzhao

    2015-01-01

    Highlights: • Aluminum and magnesium alloys were joined by underwater friction stir welding. • Underwater FSW was conducted to improve properties of joint with lower heat input. • Microstructures and mechanical properties of dissimilar joint were investigated. • Intermetallic compounds developed in the fracture interface were analyzed. • Fracture features of the tensile samples were analyzed. - Abstract: Formation of intermetallic compounds in the stir zone of dissimilar welds affects the mechanical properties of the joints significantly. In order to reduce heat input and control the amount and morphological characteristics of brittle intermetallic compounds underwater friction stir welding of 6013 Al alloy and AZ31 Mg alloy was carried out. Microstructures, mechanical properties, elements distribution, and the fracture surface of the joints were analyzed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, etc. The result shows that sound dissimilar joint with good mechanical properties can be obtained by underwater friction stir welding. Al and Mg alloys were stirred together and undergone the process of recrystallization, forming complex intercalated flow patterns in the stir zone. Tensile strength of the dissimilar joint was up to 152.3 MPa. Maximum hardness (142HV) appeared in the middle of the centerline of the specimen. Intermetallic compounds layer consisting of Al 3 Mg 2 and Mg 17 Al 12 formed in the Al/Mg interface and resulted in the fracture of the joint

  13. Neutron absorbing article

    International Nuclear Information System (INIS)

    Naum, R.G.; Owens, D.P.; Dooker, G.I.

    1981-01-01

    A neutron-absorbing article suitable for use in spent fuel racks is described. It comprises boron carbide particles, diluent particles, and a phenolic polymer cured to a continuous matrix. The diluent may be silicon carbide, graphite, amorphous carbon, alumina, or silica. The combined boron carbide-diluent phase contains no more than 2 percent B 2 O 3 , and the neutron-absorbing article contains from 20 to 40 percent phenol resin. The ratio of boron carbide to diluent particles is in the range 1:9 to 9:1

  14. Sound absorption by Menger sponge fractal.

    Science.gov (United States)

    Kawabe, Tetsuji; Miyazaki, Takatsuna; Oka, Daisuke; Koyanagi, Sin'ichiro; Hinokidani, Atsushi

    2009-05-01

    For the purpose of investigation on acoustic properties of fractals, the sound absorption coefficients are experimentally measured by using the Menger sponge which is one of typical three-dimensional fractals. From the two-microphone measurement, the frequency range of effectively absorbing sound waves is shown to broaden with degree of fractality, which comes from the fractal property of the homothetic character. It is shown that experimental features are qualitatively explained by an electrical equivalent circuit model for the Menger sponge.

  15. Corrosion Resistant Cladding by YAG Laser Welding in Underwater Environment

    International Nuclear Information System (INIS)

    Tsutomi Kochi; Toshio Kojima; Suemi Hirata; Ichiro Morita; Katsura Ohwaki

    2002-01-01

    It is known that stress-corrosion cracking (SCC) will occur in nickel-base alloys used in Reactor Pressure Vessel (RPV) and Internals of nuclear power plants. A SCC sensitivity has been evaluated by IHI in each part of RPV and Internals. There are several water level instrumentation nozzles installed in domestic BWR RPV. In water level instrumentation nozzles, 182 type nickel-base alloys were used for the welding joint to RPV. It is estimated the SCC potential is high in this joint because of a higher residual stress than the yield strength (about 400 MPa). This report will describe a preventive maintenance method to these nozzles Heat Affected Zone (HAZ) and welds by a corrosion resistant cladding (CRC) by YAG Laser in underwater environment (without draining a reactor water). There are many kinds of countermeasures for SCC, for example, Induction Heating Stress Improvement (IHSI), Mechanical Stress Improvement Process (MSIP) and so on. A YAG laser CRC is one of them. In this technology a laser beam is used for heat source and irradiated through an optical fiber to a base metal and SCC resistant material is used for welding wires. After cladding the HAZ and welds are coated by the corrosion resistant materials so their surfaces are improved. A CRC by gas tungsten arc welding (GTAW) in an air environment had been developed and already applied to a couple of operating plants (16 Nozzles). This method was of course good but it spent much time to perform because of an installation of some water-proof working boxes to make a TIG-weldability environment. CRC by YAG laser welding in underwater environment has superior features comparing to this conventional TIG method as follows. At the viewpoint of underwater environment, (1) an outage term reduction (no drainage water). (2) a radioactive exposure dose reduction for personnel. At that of YAG laser welding, (1) A narrower HAZ. (2) A smaller distortion. (3) A few cladding layers. A YAG laser CRC test in underwater

  16. Second Sound

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 6. Second Sound - The Role of Elastic Waves. R Srinivasan. General Article Volume 4 Issue 6 June 1999 pp 15-19. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/004/06/0015-0019 ...

  17. Second Sound

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 3. Second Sound - Waves of Entropy and Temperature. R Srinivasan. General Article Volume 4 Issue 3 March 1999 pp 16-24. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/004/03/0016-0024 ...

  18. Second Sound

    Indian Academy of Sciences (India)

    as a function of q is called adispersion curve. Landau postulated. R Srinivasan is a Visiting. Professor at the Raman. Research Institute after retiring as .... Second sound was seen in solid 4He crystals by Ackermann and others in 1966. 4He will not solidify even at absolute zero of temperature unless one applies a pressure ...

  19. Second Sound

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 6. Second Sound - The Role of Elastic Waves. R Srinivasan. General Article Volume 4 Issue 6 June 1999 pp 15-19. Fulltext. Click here to view fulltext PDF. Permanent link: https://www.ias.ac.in/article/fulltext/reso/004/06/0015-0019 ...

  20. Sound engineer

    CERN Document Server

    Mara, Wil

    2015-01-01

    "Readers will learn what it takes to succeed as a sound engineer. The book also explains the necessary educational steps, useful character traits, potential hazards, and daily job tasks related to this career. Sidebars include thought-provoking trivia. Questions in the backmatter ask for text-dependent analysis. Photos, a glossary, and additional resources are included."-- Provided by publisher.

  1. Sound Settlements

    DEFF Research Database (Denmark)

    Mortensen, Peder Duelund; Hornyanszky, Elisabeth Dalholm; Larsen, Jacob Norvig

    2013-01-01

    Præsentation af projektresultater fra Interreg forskningen Sound Settlements om udvikling af bæredygtighed i det almene boligbyggerier i København, Malmø, Helsingborg og Lund samt europæiske eksempler på best practice...

  2. Jellyfish inspired underwater unmanned vehicle

    Science.gov (United States)

    Villanueva, Alex; Bresser, Scott; Chung, Sanghun; Tadesse, Yonas; Priya, Shashank

    2009-03-01

    An unmanned underwater vehicle (UUV) was designed inspired by the form and functionality of a Jellyfish. These natural organisms were chosen as bio-inspiration for a multitude of reasons including: efficiency of locomotion, lack of natural predators, proper form and shape to incorporate payload, and varying range of sizes. The structure consists of a hub body surrounded by bell segments and microcontroller based drive system. The locomotion of UUV was achieved by shape memory alloy "Biometal Fiber" actuation which possesses large strain and blocking force with adequate response time. The main criterion in design of UUV was the use of low-profile shape memory alloy actuators which act as artificial muscles. In this manuscript, we discuss the design of two Jellyfish prototypes and present experimental results illustrating the performance and power consumption.

  3. Absorber for nuclear radiations

    International Nuclear Information System (INIS)

    Planchamp, C.

    1987-01-01

    Neutrons, gamma and x radiations are highly absorbed by an alloy of gadolinium and aluminium. Workability, thermal conductivity, mechanical properties, corrosion resistance of the alloy are good. Possible applications are transport or storage of radioactive wastes or nuclear fuels, fuel racks, shelters, etc [fr

  4. Low Absorbance Measurements

    Science.gov (United States)

    Harris, T. D.; Williams, A. M.

    1983-10-01

    The application of low absorption measurements to dilute solute determination requires specific instrumental characteristics. The use of laser intracavity absorption and thermal lens calorimetry to measure concentration is shown. The specific operating parameters that determine sensitivity are delineated along with the limits different measurement strategies impose. Finally areas of improvement in components that would result in improve sensitivity, accuracy, and reliability are discussed. During the past decade, a large number of methods have been developed for measuring the light absorbed by transparent materials. These include measurements on gases, liquids, and solids. The activity has been prompted by a variety of applications and a similar variety of disciplines. In Table 1 some representative examples of these methods is shown along with their published detection limits.1 It is clear that extraordinarily small absorbances can be measured. Most of the methods can be conveniently divided into two groups. These groups are those that measure the transmission of the sample and those that measure the light absorbed by the sample. The light absorbed methods are calorimetric in character. The advantages and disadvantages of each method varies depending on the principal application for which they were developed. The most prevalent motivation has been to characterize the bulk optical properties of transparent materials. Two examples are the development of extremely transparent glasses for use as fiber optic materials and the development of substrates for high power laser operation.

  5. Kenaf Core Particleboard and Its Sound Absorbing Properties

    OpenAIRE

    Mohamad Jani Saad; Izran Kamal

    2012-01-01

    In this study, kenaf (Hibiscus cannabinus) core particleboards as insulation boards were manufactured. The boards were fabricated with three different densities i.e. 350 kg/m3, 450 kg/m3 and 550 kg/m3 at urea formaldehyde resin (UF) loadings of 8%, 10% and 12% (w/w) based on the dry weight of the kenaf core particles. The fabricated boards were evaluated for its noise acoustical coefficients (NAC) by following the ASTM E1050-98 standard requirements. The study revealed that boards with higher...

  6. Underwater sympathetic detonation of pellet explosive

    Science.gov (United States)

    Kubota, Shiro; Saburi, Tei; Nagayama, Kunihito

    2017-06-01

    The underwater sympathetic detonation of pellet explosives was taken by high-speed photography. The diameter and the thickness of the pellet were 20 and 10 mm, respectively. The experimental system consists of the precise electric detonator, two grams of composition C4 booster and three pellets, and these were set in water tank. High-speed video camera, HPV-X made by Shimadzu was used with 10 Mfs. The underwater explosions of the precise electric detonator, the C4 booster and a pellet were also taken by high-speed photography to estimate the propagation processes of the underwater shock waves. Numerical simulation of the underwater sympathetic detonation of the pellet explosives was also carried out and compared with experiment.

  7. Underwater Grass Comeback Helps Chesapeake Bay

    Science.gov (United States)

    The fortified Susquehanna Flats, the largest bed of underwater grasses in the Chesapeake Bay, seems able to withstand a major weather punch. Its resilience is contributing to an overall increase in the Bay’s submerged aquatic vegetation.

  8. Underwater Object Segmentation Based on Optical Features

    Directory of Open Access Journals (Sweden)

    Zhe Chen

    2018-01-01

    Full Text Available Underwater optical environments are seriously affected by various optical inputs, such as artificial light, sky light, and ambient scattered light. The latter two can block underwater object segmentation tasks, since they inhibit the emergence of objects of interest and distort image information, while artificial light can contribute to segmentation. Artificial light often focuses on the object of interest, and, therefore, we can initially identify the region of target objects if the collimation of artificial light is recognized. Based on this concept, we propose an optical feature extraction, calculation, and decision method to identify the collimated region of artificial light as a candidate object region. Then, the second phase employs a level set method to segment the objects of interest within the candidate region. This two-phase structure largely removes background noise and highlights the outline of underwater objects. We test the performance of the method with diverse underwater datasets, demonstrating that it outperforms previous methods.

  9. Sensor network architectures for monitoring underwater pipelines.

    Science.gov (United States)

    Mohamed, Nader; Jawhar, Imad; Al-Jaroodi, Jameela; Zhang, Liren

    2011-01-01

    This paper develops and compares different sensor network architecture designs that can be used for monitoring underwater pipeline infrastructures. These architectures are underwater wired sensor networks, underwater acoustic wireless sensor networks, RF (radio frequency) wireless sensor networks, integrated wired/acoustic wireless sensor networks, and integrated wired/RF wireless sensor networks. The paper also discusses the reliability challenges and enhancement approaches for these network architectures. The reliability evaluation, characteristics, advantages, and disadvantages among these architectures are discussed and compared. Three reliability factors are used for the discussion and comparison: the network connectivity, the continuity of power supply for the network, and the physical network security. In addition, the paper also develops and evaluates a hierarchical sensor network framework for underwater pipeline monitoring.

  10. Underwater photogrammetry successful in Spain and France

    International Nuclear Information System (INIS)

    Anon.

    1988-01-01

    Underwater photogrammetry has been used to measure distortions in fuel assembly alignment pins in the upper internals of the Almarez and Dampierre PWRs. Photogrammetry is a three-dimensional precision measurement method using photographic techniques for the on-site measurement phase. On the strength of the operations at the two PWRs, underwater photogrammetry is now considered as a practical and effective technique for dimensional inspection at nuclear plants. (U.K.)

  11. Underwater noise levels in UK waters

    OpenAIRE

    Merchant, Nathan D.; Brookes, Kate L.; Faulkner, Rebecca C.; Bicknell, Anthony W. J.; Godley, Brendan J.; Witt, Matthew J.

    2016-01-01

    Underwater noise from human activities appears to be rising, with ramifications for acoustically sensitive marine organisms and the functioning of marine ecosystems. Policymakers are beginning to address the risk of ecological impact, but are constrained by a lack of data on current and historic noise levels. Here, we present the first nationally coordinated effort to quantify underwater noise levels, in support of UK policy objectives under the EU Marine Strategy Framework Directive (MSFD). ...

  12. Underwater gait analysis in Parkinson's disease.

    Science.gov (United States)

    Volpe, Daniele; Pavan, Davide; Morris, Meg; Guiotto, Annamaria; Iansek, Robert; Fortuna, Sofia; Frazzitta, Giuseppe; Sawacha, Zimi

    2017-02-01

    Although hydrotherapy is one of the physical therapies adopted to optimize gait rehabilitation in people with Parkinson disease, the quantitative measurement of gait-related outcomes has not been provided yet. This work aims to document the gait improvements in a group of parkinsonians after a hydrotherapy program through 2D and 3D underwater and on land gait analysis. Thirty-four parkinsonians and twenty-two controls were enrolled, divided into two different cohorts. In the first one, 2 groups of patients underwent underwater or land based walking training; controls underwent underwater walking training. Hence pre-treatment 2D underwater and on land gait analysis were performed, together with post-treatment on land gait analysis. Considering that current literature documented a reduced movement amplitude in parkinsonians across all lower limb joints in all movement planes, 3D underwater and on land gait analysis were performed on a second cohort of subjects (10 parkinsonians and 10 controls) who underwent underwater gait training. Baseline land 2D and 3D gait analysis in parkinsonians showed shorter stride length and slower speed than controls, in agreement with previous findings. Comparison between underwater and on land gait analysis showed reduction in stride length, cadence and speed on both parkinsonians and controls. Although patients who underwent underwater treatment exhibited significant changes on spatiotemporal parameters and sagittal plane lower limb kinematics, 3D gait analysis documented a significant (p<0.05) improvement in all movement planes. These data deserve attention for research directions promoting the optimal recovery and maintenance of walking ability. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

  13. Affordable underwater wireless optical communication using LEDs

    Science.gov (United States)

    Pilipenko, Vladimir; Arnon, Shlomi

    2013-09-01

    In recent years the need for high data rate underwater wireless communication (WC) has increased. Nowadays, the conventional technology for underwater communication is acoustic. However, the maximum data rate that acoustic technology can provide is a few kilobits per second. On the other hand, emerging applications such as underwater imaging, networks of sensors and swarms of underwater vehicles require much faster data rates. As a result, underwater optical WC, which can provide much higher data rates, has been proposed as an alternative means of communication. In addition to high data rates, affordable communication systems become an important feature in the development requirements. The outcome of these requirements is a new system design based on off-the-shelf components such as blue and green light emitting diodes (LEDs). This is due to the fact that LEDs offer solutions characterized by low cost, high efficiency, reliability and compactness. However, there are some challenges to be met when incorporating LEDs as part of the optical transmitter, such as low modulation rates and non linearity. In this paper, we review the main challenges facing the incorporation of LEDs as an integral part of underwater WC systems and propose some techniques to mitigate the LED limitations in order to achieve high data rate communication

  14. An underwater optical wireless communication network

    Science.gov (United States)

    Arnon, Shlomi

    2009-08-01

    The growing need for underwater observation and sub-sea monitoring systems has stimulated considerable interest in advancing the enabling technologies of underwater wireless communication and underwater sensor networks. This communication technology is expected to play an important role in investigating climate change, in monitoring biological, bio-geochemical, evolutionary and ecological changes in the sea, ocean and lake environments and in helping to control and maintain oil production facilities and harbors using unmanned underwater vehicles (UUVs), submarines, ships, buoys, and divers. However, the present technology of underwater acoustic communication cannot provide the high data rate required to investigate and monitor these environments and facilities. Optical wireless communication has been proposed as the best alternative to meet this challenge. We present models of three kinds of optical wireless communication links a) a line-of-sight link, b) a modulating retro-reflector link and c) a reflective link, all of which can provide the required data rate. We analyze the link performance based on these models. From the analysis, it is clear that as the water absorption increases, the communication performance decreases dramatically for the three link types. However, by using the scattered lighted it was possible to mitigate this decrease in some cases. We conclude from the analysis that a high data rate underwater optical wireless network is a feasible solution for emerging applications such as UUV to UUV links and networks of sensors, and extended ranges in these applications could be achieved by applying a multi-hop concept.

  15. PREFACE: Aerodynamic sound Aerodynamic sound

    Science.gov (United States)

    Akishita, Sadao

    2010-02-01

    The modern theory of aerodynamic sound originates from Lighthill's two papers in 1952 and 1954, as is well known. I have heard that Lighthill was motivated in writing the papers by the jet-noise emitted by the newly commercialized jet-engined airplanes at that time. The technology of aerodynamic sound is destined for environmental problems. Therefore the theory should always be applied to newly emerged public nuisances. This issue of Fluid Dynamics Research (FDR) reflects problems of environmental sound in present Japanese technology. The Japanese community studying aerodynamic sound has held an annual symposium since 29 years ago when the late Professor S Kotake and Professor S Kaji of Teikyo University organized the symposium. Most of the Japanese authors in this issue are members of the annual symposium. I should note the contribution of the two professors cited above in establishing the Japanese community of aerodynamic sound research. It is my pleasure to present the publication in this issue of ten papers discussed at the annual symposium. I would like to express many thanks to the Editorial Board of FDR for giving us the chance to contribute these papers. We have a review paper by T Suzuki on the study of jet noise, which continues to be important nowadays, and is expected to reform the theoretical model of generating mechanisms. Professor M S Howe and R S McGowan contribute an analytical paper, a valuable study in today's fluid dynamics research. They apply hydrodynamics to solve the compressible flow generated in the vocal cords of the human body. Experimental study continues to be the main methodology in aerodynamic sound, and it is expected to explore new horizons. H Fujita's study on the Aeolian tone provides a new viewpoint on major, longstanding sound problems. The paper by M Nishimura and T Goto on textile fabrics describes new technology for the effective reduction of bluff-body noise. The paper by T Sueki et al also reports new technology for the

  16. Sound Absorption of Arenga Pinnata Natural Fiber

    OpenAIRE

    Lindawati Ismail; Mohd. Imran Ghazali; Shahruddin Mahzan; Ahmad Mujahid Ahmad Zaidi

    2010-01-01

    Arenga pinnata is an abundantly natural fiber that can be used for sound proof material. However, the scientific data of acoustics properties of Arenga pinnata was not available yet. In this study the sound absorption of pure arenga pinnata was measured. The thickness of Arenga pinnata was varied in 10 mm, 20 mm, 30mm, and 40mm. This work was carried out to investigate the potential of using Arenga pinnata fiber as raw material for sound absorbing material. Impedance Tube Method was used to m...

  17. Development of underwater inspection and YAG laser repair welding robots for equipments

    International Nuclear Information System (INIS)

    Sato, Shuichi; Kojima, Toshio; Ohwaki, Katsura; Hirose, Naoya

    2000-01-01

    As equipments for power generation such as tank on bath storing wasted water, used resin and others in mainly radioactive wastes processing equipments in nuclear power plant and so forth are carried out periodical inspections and repairs to keep their soundness from long years ago, its importance seems to be increasing more and more hereafter at background of a trend of longer life in their plant. In response to such importance, development of technologies capable of remote control on inspection of inside of the equipments at underwater atmosphere and on repair welding due to YAG laser have been carried out. Here were described on necessity in remote inspection and repair technique, outlines on remote underwater inspection and repair technique, results on welding test, items on compatibility test, and their concrete examples. (G.K.)

  18. State of the art report: Underwater examination techniques for spent nuclear fuels

    International Nuclear Information System (INIS)

    Chun, Yong Bum

    1997-06-01

    In these days, much efforts are being put to increase the final discharge burnup of PWR fuels. Therefore, the necessity of the inspection of irradiated nuclear fuels assembly during the the refueling outage is greatly increased to evaluate the safe operation and soundness of fuel assemblies in their next cycles in core, and apply the results for safe operation and effective core management. The necessity to evaluate the irradiation performance of indigenous nuclear fuels pushes the relative researchers to the development of on-site fuel inspection techniques and devices which can perform the underwater inspection and measurement of irradiated nuclear fuels during refueling outage. To ensure the technologies, the status of in situ underwater fuel inspection techniques and equipment were investigated and reviewed. Those information provides the fuel inspection capability to evaluate and certificate the performance and integrity of nuclear fuels which leads to the safe operation of NPP. (author). 49 refs., 52 figs

  19. Kinetic energy absorbing pad

    International Nuclear Information System (INIS)

    Bricmont, R.J.; Hamilton, P.A.; Ming Long Ting, R.

    1981-01-01

    Reactors, fuel processing plants etc incorporate pipes and conduits for fluids under high pressure. Fractures, particularly adjacent to conduit elbows, produce a jet of liquid which whips the broken conduit at an extremely high velocity. An enormous impact load would be applied to any stationary object in the conduit's path. The design of cellular, corrugated metal impact pads to absorb the kinetic energy of the high velocity conduits is given. (U.K.)

  20. Absorbable and biodegradable polymers

    CERN Document Server

    Shalaby, Shalaby W

    2003-01-01

    INTRODUCTION NOTES: Absorbable/Biodegradable Polymers: Technology Evolution. DEVELOPMENT AND APPLICATIONOF NEW SYSTEMS: Segmented Copolyesters with Prolonged Strength Retention Profiles. Polyaxial Crystalline Fiber-Forming Copolyester. Polyethylene Glycol-Based Copolyesters. Cyanoacrylate-Based Systems as Tissue Adhesives. Chitosan-Based Systems. Hyaluronic Acid-Based Systems. DEVELOPMENTS IN PREPARATIVE, PROCESSING, AND EVALUATION METHODS: New Approaches to the Synthesis of Crystalline. Fiber-Forming Aliphatic Copolyesters. Advances in Morphological Development to Tailor the Performance of Me

  1. Burnable neutron absorbers

    International Nuclear Information System (INIS)

    Radford, K.C.; Carlson, W.G.

    1985-01-01

    This patent deals with the fabrication of pellets for neutron absorber rods. Such a pellet includes a matrix of a refractory material which may be aluminum or zirconium oxide, and a burnable poison distributed throughout the matrix. The neutron absorber material may consist of one or more elements or compounds of the metals boron, gadolinium, samarium, cadmium, europium, hafnium, dysprosium and indium. The method of fabricating pellets of these materials outlined in this patent is designed to produce pores or voids in the pellets that can be used to take up the expansion of the burnable poison and to absorb the helium gas generated. In the practice of this invention a slurry of Al 2 O 3 is produced. A hard binder is added and the slurry and binder are spray dried. This powder is mixed with dry B 4 C powder, forming a homogeneous mixture. This mixture is pressed into green tubes which are then sintered. During sintering the binder volatilizes leaving a ceramic with nearly spherical high-density regions of

  2. Characterizing large river sounds: Providing context for understanding the environmental effects of noise produced by hydrokinetic turbines.

    Science.gov (United States)

    Bevelhimer, Mark S; Deng, Z Daniel; Scherelis, Constantin

    2016-01-01

    Underwater noise associated with the installation and operation of hydrokinetic turbines in rivers and tidal zones presents a potential environmental concern for fish and marine mammals. Comparing the spectral quality of sounds emitted by hydrokinetic turbines to natural and other anthropogenic sound sources is an initial step at understanding potential environmental impacts. Underwater recordings were obtained from passing vessels and natural underwater sound sources in static and flowing waters. Static water measurements were taken in a lake with minimal background noise. Flowing water measurements were taken at a previously proposed deployment site for hydrokinetic turbines on the Mississippi River, where sounds created by flowing water are part of all measurements, both natural ambient and anthropogenic sources. Vessel sizes ranged from a small fishing boat with 60 hp outboard motor to an 18-unit barge train being pushed upstream by tugboat. As expected, large vessels with large engines created the highest sound levels, which were, on average, 40 dB greater than the sound created by an operating hydrokinetic turbine. A comparison of sound levels from the same sources at different distances using both spherical and cylindrical sound attenuation functions suggests that spherical model results more closely approximate observed sound attenuation.

  3. Sound absorption and reflection with coupled tubes

    NARCIS (Netherlands)

    van der Eerden, F.J.M.

    2000-01-01

    This paper describes a special sound absorbing technique with an accompanying efficient numerical design tool. As a basis pressure waves in a single narrow tube or pore are considered. In such a tube the viscosity and the thermal conductivity of the air, or any other fluid, can have a significant

  4. A new signal development process and sound system for diverting fish from water intakes

    International Nuclear Information System (INIS)

    Klinet, D.A.; Loeffelman, P.H.; van Hassel, J.H.

    1992-01-01

    This paper reports that American Electric Power Service Corporation has explored the feasibility of using a patented signal development process and underwater sound system to divert fish away from water intake areas. The effect of water intakes on fish is being closely scrutinized as hydropower projects are re-licensed. The overall goal of this four-year research project was to develop an underwater guidance system which is biologically effective, reliable and cost-effective compared to other proposed methods of diversion, such as physical screens. Because different fish species have various listening ranges, it was essential to the success of this experiment that the sound system have a great amount of flexibility. Assuming a fish's sounds are heard by the same kind of fish, it was necessary to develop a procedure and acquire instrumentation to properly analyze the sounds that the target fish species create to communicate and any artificial signals being generated for diversion

  5. Acoustical model of a Shoddy fibre absorber

    Science.gov (United States)

    Manning, John Peter

    Shoddy fibres or "Shoddies" are a mixture of post-consumer and post-industrial fibres diverted from textile waste streams and recycled into their raw fibre form. They have found widespread use as a raw material for manufacturing sound absorbers that include, but are not limited to: automotive, architectural and home appliance applications. The purpose of this project is to develop a simple acoustic model to describe the acoustic behaviour of sound absorbers composed primarily of Shoddy fibres. The model requires knowledge of the material's bulk density only. To date, these materials have not been the focus of much published research and acoustical designers must rely on models that were developed for other materials or are overly complex. For modelling purposes, an equivalent fluid approach is chosen to balance complexity and accuracy. In deriving the proposed model, several popular equivalent fluid models are selected and the required input parameters for each model identified. The models are: the model of Delaney and Bazley, two models by Miki, the model of Johnson in conjunction with the model of Champoux and Allard and the model of Johnson in conjunction with the model of Lafarge. Characterization testing is carried out on sets of Shoddy absorbers produced using three different manufacturing methods. The measured properties are open porosity, tortuosity, airflow resistivity, the viscous and thermal characteristic lengths and the static thermal permeability. Empirical relationships between model parameters and bulk density are then derived and used to populate the selected models. This yields several 'simplified' models with bulk density as the only parameter. The most accurate model is then selected by comparing each model's prediction to the results of normal incidence sound absorption tests. The model of Johnson-Lafarge populated with the empirical relations is the most accurate model over the range of frequencies considered (approx. 300 Hz - 4000 Hz

  6. Decay of reverberant sound in a spherical enclosure

    International Nuclear Information System (INIS)

    Carroll, M.M.; Chien, C.F.

    1977-01-01

    The assumption of diffuse reflection (Lambert's Law) leads to integral equations for the wall intensity in a reverberant sound field in the steady state and during decay. The latter equation, in the special case of a spherical enclosure with uniformly absorbent walls and uniform wall intensity, allows exponential decay with a decay time which agrees closely with the Norris--Eyring prediction. The sound-intensity and sound-energy density in the medium, during decay, are also calculated

  7. Absorber for terahertz radiation management

    Science.gov (United States)

    Biallas, George Herman; Apeldoorn, Cornelis; Williams, Gwyn P.; Benson, Stephen V.; Shinn, Michelle D.; Heckman, John D.

    2015-12-08

    A method and apparatus for minimizing the degradation of power in a free electron laser (FEL) generating terahertz (THz) radiation. The method includes inserting an absorber ring in the FEL beam path for absorbing any irregular THz radiation and thus minimizes the degradation of downstream optics and the resulting degradation of the FEL output power. The absorber ring includes an upstream side, a downstream side, and a plurality of wedges spaced radially around the absorber ring. The wedges form a scallop-like feature on the innermost edges of the absorber ring that acts as an apodizer, stopping diffractive focusing of the THz radiation that is not intercepted by the absorber. Spacing between the scallop-like features and the shape of the features approximates the Bartlett apodization function. The absorber ring provides a smooth intensity distribution, rather than one that is peaked on-center, thereby eliminating minor distortion downstream of the absorber.

  8. Underwater Noise Modeling in Lithuanian Area of the Baltic Sea

    Directory of Open Access Journals (Sweden)

    Donatas Bagočius

    2017-09-01

    Full Text Available Along with rising awareness of public and scientific societies about environmental and ecological impacts of underwater noise, the need for underwater noise modelling in the shallow Lithuanian area of Baltic Sea emerged. Marine Strategy Framework Directive issues regarding underwater noise indicators refers to possibility of evaluation of Good Environmental State using underwater noise measurements as well as possibility to model underwater noise. Main anthropogenic underwater noise contributor in the Seas is the shipping lanes as known due to date, with no exclusion of Lithuanian Baltic Sea area. In this manuscript, it is presented the methods of development of simplistic underwater ambient noise model purposed for computation of underwater soundscape in shallow area of the Lithuanian Baltic Sea.

  9. Underwater Sensor Networks: A New Energy Efficient and Robust Architecture

    NARCIS (Netherlands)

    Climent, Salvador; Capella, Juan Vincente; Meratnia, Nirvana; Serrano, Juan José

    2012-01-01

    The specific characteristics of underwater environments introduce new challenges for networking protocols. In this paper, a specialized architecture for underwater sensor networks (UWSNs) is proposed and evaluated. Experiments are conducted in order to analyze the suitability of this protocol for

  10. Passive, broadband suppression of radiation of low-frequency sound.

    Science.gov (United States)

    Godin, Oleg A; Baynes, Alexander B

    2018-02-01

    Anthropogenic noise pollution of the ocean is an acute and growing problem. This letter explores one possible mechanism of noise abatement. The far-field acoustic pressure due to a compact underwater source can be suppressed by placing a small compliant body in the vicinity of the source. Here, the feasibility and efficiency of the suppression are evaluated by quantifying the reduction in radiated acoustic energy for several simple geometries, which include sound sources in an unbounded fluid, near a reflecting boundary, or in a shallow-water waveguide. The analysis is streamlined using analytic solutions for sound diffraction by simple shapes.

  11. Magnetohydrodynamic underwater vehicular propulsion systems

    International Nuclear Information System (INIS)

    Swallom, D.W.; Sadovnik, I.; Gibbs, J.S.; Gurol, H.; Nguyen, L.

    1990-01-01

    The development of magnetohydrodynamic propulsion systems for underwater vehicles is discussed. According to the authors, it is a high risk endeavor that offers the possibility of a number of significant advantages over conventional propeller propulsion systems. These advantages may include the potential for greater stealth characteristics, increased maneuverability, enhanced survivability, elimination of cavitation limits, and addition of a significant emergency propulsion system. The possibility of increased stealth is by far the most important advantage. A conceptual design study has been completed with numerical results that shows that these advantages may be obtained with a magnetohydrodynamic propulsion system in an annular configuration externally surrounding a generic study submarine that is neutrally buoyant and can operate with the existing submarine propulsion system power plant. The classical submarine mission requirements make the use of these characteristics of the magnetohydrodynamic propulsion system particularly appropriate for submarine missions. The magnetohydrodynamic annular propulsion system for a generic attack class submarine has been designed to take advantage of the magnetohydrodynamic thruster characteristics

  12. Routing strategies for underwater gliders

    Science.gov (United States)

    Davis, Russ E.; Leonard, Naomi E.; Fratantoni, David M.

    2009-02-01

    Gliders are autonomous underwater vehicles that achieve long operating range by moving at speeds comparable to those of, or slower than, typical ocean currents. This paper addresses routing gliders to rapidly reach a specified waypoint or to maximize the ability to map a measured field, both in the presence of significant currents. For rapid transit in a frozen velocity field, direct minimization of travel time provides a trajectory "ray" equation. A simpler routing algorithm that requires less information is also discussed. Two approaches are developed to maximize the mapping ability, as measured by objective mapping error, of arrays of vehicles. In order to produce data sets that are readily interpretable, both approaches focus sampling near predetermined "ideal tracks" by measuring mapping skill only on those tracks, which are laid out with overall mapping skill in mind. One approach directly selects each vehicle's headings to maximize instantaneous mapping skill integrated over the entire array. Because mapping skill decreases when measurements are clustered, this method automatically coordinates glider arrays to maintain spacing. A simpler method that relies on manual control for array coordination employs a first-order control loop to balance staying close to the ideal track and maintaining vehicle speed to maximize mapping skill. While the various techniques discussed help in dealing with the slow speed of gliders, nothing can keep performance from being degraded when current speeds are comparable to vehicle speed. This suggests that glider utility could be greatly enhanced by the ability to operate high speeds for short periods when currents are strong.

  13. Impact of internal waves on sound propagation off Bhimilipatnam, east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Sridevi, B.; Murty, T.V.R.; Sadhuram, Y.; Rao, M.M.M.; Maneesha, K.; SujithKumar, S.; Prasanna, P.L.

    -259 Impact of internal waves on sound propagation off Bhimilipatnam, East coast of India B.Sridevi, T.V. Ramana Murty, Y. Sadhuram, M.M.M. Rao, K. Maneesha, S. Sujith Kumar and P.L. Prasanna National Institute of Oceanography, Regional center, 176... the variability of ocean environment rather than it’s mean. Oceanic changes relevant to underwater acoustics are classified into mean and fluctuating components (De Santo 1979) with the following general model of the sound velocity equation...

  14. Underwater noise from a wave energy converter

    DEFF Research Database (Denmark)

    Tougaard, Jakob

    in full operation and start and stop of the converter. Median broad band (10 Hz – 20 kHz) sound pressure level (Leq) was 123 dB re. 1 Pa, irrespective of status of the wave energy converter (stopped, running or starting/stopping). The most pronounced peak in the third-octave spectrum was in the 160 Hz...... band during start and stop of the converter, attributed to the hydraulic pump responsible for lifting and lowering the absorbers. Less pronounced, but still statistically significant differences were seen in the bands 125, 160, 200 and 250 Hz when operation and ambient were compared. No statistically...... significant noise above ambient could be detected above the 250 Hz band. The absolute increase in noise above ambient was very small. L50 third-octave levels in the four bands with the converter running were thus only 1-2 dB above ambient L50 levels. The noise recorded 25 m from the wave energy converter...

  15. Corrosion resistant neutron absorbing coatings

    Science.gov (United States)

    Choi, Jor-Shan [El Cerrito, CA; Farmer, Joseph C [Tracy, CA; Lee, Chuck K [Hayward, CA; Walker, Jeffrey [Gaithersburg, MD; Russell, Paige [Las Vegas, NV; Kirkwood, Jon [Saint Leonard, MD; Yang, Nancy [Lafayette, CA; Champagne, Victor [Oxford, PA

    2012-05-29

    A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

  16. Insights into Optimal Soft Start and Shutdown Procedures for Stationary or Moving Sound Sources

    NARCIS (Netherlands)

    Ainslie, M.A.; Benda-Beckmann, A.M. von

    2012-01-01

    To reduce the risk of impact on marine life of underwater sound generated by anthropogenic activities (such as offshore construction, seismic surveys and sonar searches), various mitigation measures are often put in place. Two commonly adopted mitigation measures are the soft start (or "ramp-up" –

  17. Solar radiation absorbing material

    Science.gov (United States)

    Googin, John M.; Schmitt, Charles R.; Schreyer, James M.; Whitehead, Harlan D.

    1977-01-01

    Solar energy absorbing means in solar collectors are provided by a solar selective carbon surface. A solar selective carbon surface is a microporous carbon surface having pores within the range of 0.2 to 2 micrometers. Such a surface is provided in a microporous carbon article by controlling the pore size. A thermally conductive substrate is provided with a solar selective surface by adhering an array of carbon particles in a suitable binder to the substrate, a majority of said particles having diameters within the range of about 0.2-10 microns.

  18. Impact of Vessel Noise on Oyster Toadfish (Opsanus tau) Behavior and Implications for Underwater Noise Management

    Science.gov (United States)

    Krahforst, Cecilia S.

    Underwater noise and its impacts on marine life are growing management concerns. This dissertation considers both the ecological and social concerns of underwater noise, using the oyster toadfish (Opsanus tau) as a model species. Oyster toadfish call for mates using a boatwhistle sound, but increased ambient noise levels from vessels or other anthropogenic activities are likely to influence the ability of males to find mates. If increased ambient noise levels reduce fish fitness then underwater noise can impact socially valued ecosystem services (e.g. fisheries). The following ecological objectives of the impacts of underwater noise on oyster toadfish were investigated: (1) to determine how noise influences male calling behavior; (2) to assess how areas of high vessel activity ("noisy") and low vessel activity ("quiet") influence habitat utilization (fish standard length and occupancy rate); and (3) to discover if fitness (number of clutches and number of embryos per clutch) is lower in "noisy" compared with "quiet" sites. Field experiments were executed in "noisy" and "quiet" areas. Recorded calls by males in response to playback sounds (vessel, predator, and snapping shrimp sounds) and egg deposition by females ("noisy" vs. "quiet" sites) demonstrated that oyster toadfish are impacted by underwater noise. First, males decreased their call rates and called louder in response to increased ambient noise levels. Second, oyster toadfish selected nesting sites in areas with little or no inboard motorboat activity. Third, male oyster toadfish at "noisy" sites either had no egg clutches on their shelters or the number of embryos per clutch was significantly lower than in the "quiet" areas. Underwater noise and disturbance from vessels are influencing the fitness of the oyster toadfish. The social significance of the growing concerns regarding underwater noise was investigated by identifying dominant themes found within two types of texts: four recent underwater noise

  19. Survivability design for a hybrid underwater vehicle

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Biao; Wu, Chao; Li, Xiang; Zhao, Qingkai; Ge, Tong [State Key Lab of Ocean Engineering, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2015-03-10

    A novel hybrid underwater robotic vehicle (HROV) capable of working to the full ocean depth has been developed. The battery powered vehicle operates in two modes: operate as an untethered autonomous vehicle in autonomous underwater vehicle (AUV) mode and operate under remote control connected to the surface vessel by a lightweight, fiber optic tether in remotely operated vehicle (ROV) mode. Considering the hazardous underwater environment at the limiting depth and the hybrid operating modes, survivability has been placed on an equal level with the other design attributes of the HROV since the beginning of the project. This paper reports the survivability design elements for the HROV including basic vehicle design of integrated navigation and integrated communication, emergency recovery strategy, distributed architecture, redundant bus, dual battery package, emergency jettison system and self-repairing control system.

  20. Survivability design for a hybrid underwater vehicle

    International Nuclear Information System (INIS)

    Wang, Biao; Wu, Chao; Li, Xiang; Zhao, Qingkai; Ge, Tong

    2015-01-01

    A novel hybrid underwater robotic vehicle (HROV) capable of working to the full ocean depth has been developed. The battery powered vehicle operates in two modes: operate as an untethered autonomous vehicle in autonomous underwater vehicle (AUV) mode and operate under remote control connected to the surface vessel by a lightweight, fiber optic tether in remotely operated vehicle (ROV) mode. Considering the hazardous underwater environment at the limiting depth and the hybrid operating modes, survivability has been placed on an equal level with the other design attributes of the HROV since the beginning of the project. This paper reports the survivability design elements for the HROV including basic vehicle design of integrated navigation and integrated communication, emergency recovery strategy, distributed architecture, redundant bus, dual battery package, emergency jettison system and self-repairing control system

  1. Recent developments in underwater repair welding

    International Nuclear Information System (INIS)

    Offer, H.P.; Chapman, T.L.; Willis, E.R.; Maslakowski, J.; Van Diemen, P.; Smith, B.W.

    2001-01-01

    As nuclear plants age and reactor internal components begin to show increased evidence of age-related phenomena such as corrosion and fatigue, interest in the development of cost-effective mitigation and repair remedies grows. One technology currently receiving greater development and application program focus is underwater welding. Underwater welding, as used herein, is the application of weld metal to a substrate surface that is wet, but locally dry in the immediate area surrounding the welding torch. The locally dry environment is achieved by the use of a mechanical device that is specifically designed for water exclusion from the welding torch, surface to be welded, and the welding groove. This paper will explore recent developments in the use of underwater welding as a mitigation and repair technique. (author)

  2. Theory and application of a new method for the in-situ measurement of sound absorption

    NARCIS (Netherlands)

    Kuipers, E.R.; Wijnant, Ysbrand H.; de Boer, Andries; Klemenz, M.

    2011-01-01

    In many applications of noise control engineering, knowledge about the sound-absorbing properties of acoustically reacting surfaces is essential. Being able to measure sound absorption of surfaces in-situ, i.e. at the site but also for the actual sound source, is very useful and would eliminate the

  3. Development and application of a new method for the in-situ measurement of sound apsorption

    NARCIS (Netherlands)

    Wijnant, Ysbrand H.; Kuipers, E.R.; de Boer, Andries; Sas, P

    2010-01-01

    In many applications of noise control engineering, knowledge about the sound-absorbing properties of acoustically reacting surfaces is essential. Being able to measure sound absorption of surfaces in-situ, i.e. at the site but also for the actual sound source, would prove very useful for this reason

  4. Behavioural effects of exposure to underwater explosions in humpback whales (Megaptera novaeangliae)

    Energy Technology Data Exchange (ETDEWEB)

    Todd, S.; Lien, J.; Marques, F. [Memorial Univ. of Newfoundland, St. John`s, NF (Canada); Stevick, P. [College of the Atlantic, Bar Harbor, ME (United States); Ketten, D. [Harvard Univ., Cambridge, MA (United States). Medical School

    1996-09-01

    Findings of a study of high rate of entrapment in nets of humpback whales off the coast of northeastern Newfoundland in 1991-92 were reported. The entrapments took place in the southern portion of Trinity Bay, a site associated with construction operations, including explosions and drilling, that was assumed to have modified the underwater acoustic environment. Results indicated few behavioural reactions to detonations by the whales when measured in terms of decreased residency, overall movements, or general behaviour. However, there is tentative evidence that the increased entrapment rate may have been influenced by the long-term effects of exposure to abnormally high sound levels. 46 refs.

  5. Data-based depth estimation of an incoming autonomous underwater vehicle.

    Science.gov (United States)

    Yang, T C; Xu, Wen

    2016-10-01

    The data-based method for estimating the depth of a moving source is demonstrated experimentally for an incoming autonomous underwater vehicle traveling toward a vertical line array (VLA) of receivers at constant speed/depth. The method assumes no information on the sound-speed and bottom profile. Performing a wavenumber analysis of a narrowband signal for each hydrophone, the energy of the (modal) spectral peaks as a function of the receiver depth is used to estimate the depth of the source, traveling within the depth span of the VLA. This paper reviews the theory, discusses practical implementation issues, and presents the data analysis results.

  6. How Might We Assess and Manage the Effects of Underwater Noise on Populations of Marine Animals?

    Science.gov (United States)

    Tasker, Mark L

    2016-01-01

    The European Union Marine Strategy Framework Directive (MSFD) aims to achieve good environmental status (GES) in European seas by 2020. One of the features of GES is that underwater sound should not adversely affect the marine environment. Direct injury of marine life may occur, but a more pervasive effect is likely to be through the cumulative indirect effects on behavior. Assessing the significance of these effects on an ecosystem scale is difficult. If subsequent management of these effects is required, complex and challenging international decisions will be required.

  7. Efficient Modelling Methodology for Reconfigurable Underwater Robots

    DEFF Research Database (Denmark)

    Nielsen, Mikkel Cornelius; Blanke, Mogens; Schjølberg, Ingrid

    2016-01-01

    This paper considers the challenge of applying reconfigurable robots in an underwater environment. The main result presented is the development of a model for a system comprised of N, possibly heterogeneous, robots dynamically connected to each other and moving with 6 Degrees of Freedom (DOF......). This paper presents an application of the Udwadia-Kalaba Equation for modelling the Reconfigurable Underwater Robots. The constraints developed to enforce the rigid connection between robots in the system is derived through restrictions on relative distances and orientations. To avoid singularities...... in the orientation and, thereby, allow the robots to undertake any relative configuration the attitude is represented in Euler parameters....

  8. Underwater laser cutting of metallic structures

    International Nuclear Information System (INIS)

    Alfille, J.P.; Schildknecht, J.; Ramaswami, V.S.

    1993-01-01

    In the frame of an european contract, the feasibility of the underwater cutting with a CO 2 laser power is studied. The aim of this work is the dismantling metallic structures of reactors pools. The paper analyzes the general concept of the experimental device, the underwater cutting head, the experimenting vessel, examples of cuttings in dismantling situation with a 500 W CO 2 laser, and examples of cuttings with a 5 kW CO 2 laser. (author). 2 refs., 9 figs., 2 tabs

  9. Underwater noise from offshore oil production vessels.

    Science.gov (United States)

    Erbe, Christine; McCauley, Robert; McPherson, Craig; Gavrilov, Alexander

    2013-06-01

    Underwater acoustic recordings of six Floating Production Storage and Offloading (FPSO) vessels moored off Western Australia are presented. Monopole source spectra were computed for use in environmental impact assessments of underwater noise. Given that operations on the FPSOs varied over the period of recording, and were sometimes unknown, the authors present a statistical approach to noise level estimation. No significant or consistent aspect dependence was found for the six FPSOs. Noise levels did not scale with FPSO size or power. The 5th, 50th (median), and 95th percentile source levels (broadband, 20 to 2500 Hz) were 188, 181, and 173 dB re 1 μPa @ 1 m, respectively.

  10. Sound Search Engine Concept

    DEFF Research Database (Denmark)

    2006-01-01

    Sound search is provided by the major search engines, however, indexing is text based, not sound based. We will establish a dedicated sound search services with based on sound feature indexing. The current demo shows the concept of the sound search engine. The first engine will be realased June...

  11. Metamaterial electromagnetic wave absorbers.

    Science.gov (United States)

    Watts, Claire M; Liu, Xianliang; Padilla, Willie J

    2012-06-19

    The advent of negative index materials has spawned extensive research into metamaterials over the past decade. Metamaterials are attractive not only for their exotic electromagnetic properties, but also their promise for applications. A particular branch-the metamaterial perfect absorber (MPA)-has garnered interest due to the fact that it can achieve unity absorptivity of electromagnetic waves. Since its first experimental demonstration in 2008, the MPA has progressed significantly with designs shown across the electromagnetic spectrum, from microwave to optical. In this Progress Report we give an overview of the field and discuss a selection of examples and related applications. The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established. Insight is given into what we can expect from this rapidly expanding field and future challenges will be addressed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Heterogeneous neutron absorbers development

    International Nuclear Information System (INIS)

    Boccaccini, Aldo; Agueda, Horacio; Russo, Diego; Perez, Edmundo

    1987-01-01

    The use of solid burnable absorber materials in power light water reactors has increased in the last years, specially due to improvements attained in costs of generated electricity. The present work summarizes the basic studies made on an alumina-gadolinia system, where alumina is the inert matrix and gadolinia acts as burnable poison, and describes the fabrication method of pellets with that material. High density compacts were obtained in the range of concentrations used by cold pressing and sintering at 1600 deg C in inert (Ar) atmosphere. Finally, the results of the irradiation experiences made at RA-6 reactor, located at the Bariloche Atomic Center, are given where variations on negative reactivity caused by introduction of burnable poison rods were measured. The results obtained from these experiences are in good agreement with those coming from calculation codes. (Author)

  13. IVO develops a new repair technique for underwater sites. Viscous doughlike substance underwater cracks

    Energy Technology Data Exchange (ETDEWEB)

    Klingstedt, G.; Leisio, C. [ed.

    1998-07-01

    A viscous sealant is revolutionizing repair of the stone and concrete masonry of underwater dams, bridges and canals. There is now no need for expensive and time-consuming cofferdams, since a diver can extrude quick-setting mortar into underwater structures needing repair. This technique has worked well in recent years in various parts of Finland even in strongly flowing water. IVO experts are now starting to look more beyond the borders of Finland

  14. NASA Space Sounds API

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA has released a series of space sounds via sound cloud. We have abstracted away some of the hassle in accessing these sounds, so that developers can play with...

  15. Aperiodic-metamaterial-based absorber

    Directory of Open Access Journals (Sweden)

    Quanlong Yang

    2017-09-01

    Full Text Available The periodic-metamaterial-based perfect absorber has been studied broadly. Conversely, if the unit cell in the metamaterial-based absorber is arranged aperiodically (aperiodic-metamaterial-based absorber, how does it perform? Inspired by this, here we present a systematic study of the aperiodic-metamaterial-based absorber. By investigating the response of metamaterial absorbers based on periodic, Fibonacci, Thue-Morse, and quasicrystal lattices, we found that aperiodic-metamaterial-based absorbers could display similar absorption behaviors as the periodic one in one hand. However, their absorption behaviors show different tendency depending on the thicknesses of the spacer. Further studies on the angle and polarization dependence of the absorption behavior are also presented.

  16. Underwater Advanced Time-Domain Electromagnetic System

    Science.gov (United States)

    2017-03-03

    sufficiently waterproofed ...................................................................... 20 Objective: Calibration method can be used both topside... additional background variability is observed at early times, as illustrated in Figure 15. The layout of this figure is the same as Figure 14. Now the...are discussed in the following sections and summarized in Table 5. Objective: System is sufficiently waterproofed The array remained underwater up to

  17. Underwater Adhesives Retrofit Pipelines with Advanced Sensors

    Science.gov (United States)

    2015-01-01

    Houston-based Astro Technology Inc. used a partnership with Johnson Space Center to pioneer an advanced fiber-optic monitoring system for offshore oil pipelines. The company's underwater adhesives allow it to retrofit older deepwater systems in order to measure pressure, temperature, strain, and flow properties, giving energy companies crucial data in real time and significantly decreasing the risk of a catastrophe.

  18. Detection of Underwater UXOs in Mud

    Science.gov (United States)

    2013-04-01

    2nd International Conference on Underwater Acoustic Measurements, Crete, Greece, 2007. 16 [10] P.T. Gough and D.W. Hawkins “Imaging algorithms...course. Runs 275 and 325 folla.v the same trad < and run 322 foUows a track on the opposite side of the swath. The LF SAS image of run 325 is shown

  19. Adaptive turbo equalization for underwater acoustic communication

    NARCIS (Netherlands)

    Cannelli, L; Leus, G.; Dol, H.S.; Walree, P.A. van

    2013-01-01

    In this paper a multiband transceiver designed for underwater channels is presented. Multi-branch filtering at the receiver is used to leverage the diversity offered by a multi-scale multi-lag scenario. The multi-branch bank of filters is constructed by estimating scale and delay coefficients

  20. Underwater noise generated by offshore pile driving

    NARCIS (Netherlands)

    Tsouvalas, A.

    2015-01-01

    Anthropogenic noise emission in the marine environment has always been an environmental issue of serious concern. In particular, the noise generated during the installation of foundation piles is considered to be one of the most significant sources of underwater noise pollution. This is mainly

  1. Evolution: Fossil Ears and Underwater Sonar.

    Science.gov (United States)

    Lambert, Olivier

    2016-08-22

    A key innovation in the history of whales was the evolution of a sonar system together with high-frequency hearing. Fossils of an archaic toothed whale's inner ear bones provide clues for a stepwise emergence of underwater echolocation ability. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Impacts of underwater noise on marine vertebrates

    NARCIS (Netherlands)

    Liebschner, Alexander; Seibel, Henrike; Teilmann, Jonas; Wittekind, Dietrich; Parmentier, Eric; Dähne, Michael; Dietz, Rune; Driver, Jörg; Elk, van Cornelis; Everaarts, Eligius; Findeisen, Henning; Kristensen, Jacob; Lehnert, Kristina; Lucke, Klaus; Merck, Thomas; Müller, Sabine; Pawliczka, Iwona; Ronnenberg, Katrin; Rosenberger, Tanja; Ruser, Andreas; Tougaard, Jakob; Schuster, Max; Sundermeyer, Janne; Sveegaard, Signe; Siebert, Ursula

    2016-01-01

    The project conducts application-oriented research on impacts of underwater noise on marine vertebrates in the North and Baltic Seas. In distinct subprojects, the hearing sensitivity of harbor porpoises and gray seals as well as the acoustic tolerance limit of harbor porpoises to impulsive noise

  3. Sound Ecologies

    Directory of Open Access Journals (Sweden)

    Michelle Duffy

    2010-02-01

    Full Text Available Discussions about what constitutes ‘the rural’ invariably focus on notions of spatial location – of inhabiting spaces apart from that of the metropolitan. Deeply embedded in our images of what it means to be Australian, nonetheless our intellectual framing of ‘the rural’ as something outback and beyond has significant implications for our relations with these spaces. The relatively recent phenomenon of sea- and tree-changes has struck many unawares, and not simply because a good latté is so hard to find. Although a frivolous remark, such an apparent lack does shift our focus to a bodily scale of the rural; how is rural place re/made through our experiences of it? This article originates out of on-going research that explores the practice of listening and sound and the ways in which the body can draw attention to the intuitive, emotional, and psychoanalytical processes of subjectivity and place-making. Drawing on Nigel Thrift’s concept of an ecology of place, I suggest that contemporary heightened concerns with regards to loss and lack in rural Australia has led to a nascent emotional economy – one in which individual and intimate connections to the rural require a rethinking of how we live community and belonging. In such a terrain, what does it mean to be rural?

  4. Sound ecologies

    Directory of Open Access Journals (Sweden)

    Duffy, Michelle

    2010-01-01

    Full Text Available Discussions about what constitutes ‘the rural’ invariably focus on notions of spatial location – of inhabiting spaces apart from that of the metropolitan. Deeply embedded in our images of what it means to be Australian, nonetheless our intellectual framing of ‘the rural’ as something outback and beyond has significant implications for our relations with these spaces. The relatively recent phenomenon of sea- and tree-changes has struck many unawares, and not simply because a good latté is so hard to find. Although a frivolous remark, such an apparent lack does shift our focus to a bodily scale of the rural; how is rural place re/made through our experiences of it? This article originates out of on-going research that explores the practice of listening and sound and the ways in which the body can draw attention to the intuitive, emotional, and psychoanalytical processes of subjectivity and place-making. Drawing on Nigel Thrift’s concept of an ecology of place, I suggest that contemporary heightened concerns with regards to loss and lack in rural Australia has led to a nascent emotional economy – one in which individual and intimate connections to the rural require a rethinking of how we live community and belonging. In such a terrain, what does it mean to be rural?

  5. Underwater radiated noise from Point Absorbing Wave Energy Converters : Noise Characteristics and Possible Environmental Effects

    OpenAIRE

    Haikonen, Kalle

    2014-01-01

    The conversion of wave energy into electrical energy has the potential to become a clean and sustainable form of renewable energy conversion. However, like all forms of energy conversion it will inevitably have an impact on the marine environment, although not in the form of emissions of hazardous substances (gases, oils or chemicals associated with anticorrosion). Possible environmental issues associated with wave energy conversion include electromagnetic fields, alteration of sedimentation ...

  6. Measurement of Underwater Operational Noise Emitted by Wave and Tidal Stream Energy Devices.

    Science.gov (United States)

    Lepper, Paul A; Robinson, Stephen P

    2016-01-01

    The increasing international growth in the development of marine and freshwater wave and tidal energy harvesting systems has been followed by a growing requirement to understand any associated underwater impact. Radiated noise generated during operation is dependent on the device's physical properties, the sound-propagation environment, and the device's operational state. Physical properties may include size, distribution in the water column, and mechanics/hydrodynamics. The sound-propagation environment may be influenced by water depth, bathymetry, sediment type, and water column acoustic properties, and operational state may be influenced by tidal cycle and wave height among others This paper discusses some of the challenges for measurement of noise characteristics from these devices as well as a case study of the measurement of radiated noise from a full-scale wave energy converter.

  7. Coupled Modeling of Hydrodynamics and Sound in Coastal Ocean for Renewable Ocean Energy Development

    Energy Technology Data Exchange (ETDEWEB)

    Long, Wen; Jung, Ki Won; Yang, Zhaoqing; Copping, Andrea; Deng, Z. Daniel

    2016-03-01

    An underwater sound model was developed to simulate sound propagation from marine and hydrokinetic energy (MHK) devices or offshore wind (OSW) energy platforms. Finite difference methods were developed to solve the 3D Helmholtz equation for sound propagation in the coastal environment. A 3D sparse matrix solver with complex coefficients was formed for solving the resulting acoustic pressure field. The Complex Shifted Laplacian Preconditioner (CSLP) method was applied to solve the matrix system iteratively with MPI parallelization using a high performance cluster. The sound model was then coupled with the Finite Volume Community Ocean Model (FVCOM) for simulating sound propagation generated by human activities, such as construction of OSW turbines or tidal stream turbine operations, in a range-dependent setting. As a proof of concept, initial validation of the solver is presented for two coastal wedge problems. This sound model can be useful for evaluating impacts on marine mammals due to deployment of MHK devices and OSW energy platforms.

  8. Stability analysis of hybrid-driven underwater glider

    Science.gov (United States)

    Niu, Wen-dong; Wang, Shu-xin; Wang, Yan-hui; Song, Yang; Zhu, Ya-qiang

    2017-10-01

    Hybrid-driven underwater glider is a new type of unmanned underwater vehicle, which combines the advantages of autonomous underwater vehicles and traditional underwater gliders. The autonomous underwater vehicles have good maneuverability and can travel with a high speed, while the traditional underwater gliders are highlighted by low power consumption, long voyage, long endurance and good stealth characteristics. The hybrid-driven underwater gliders can realize variable motion profiles by their own buoyancy-driven and propeller propulsion systems. Stability of the mechanical system determines the performance of the system. In this paper, the Petrel-II hybrid-driven underwater glider developed by Tianjin University is selected as the research object and the stability of hybrid-driven underwater glider unitedly controlled by buoyancy and propeller has been targeted and evidenced. The dimensionless equations of the hybrid-driven underwater glider are obtained when the propeller is working. Then, the steady speed and steady glide path angle under steady-state motion have also been achieved. The steady-state operating conditions can be calculated when the hybrid-driven underwater glider reaches the desired steady-state motion. And the steadystate operating conditions are relatively conservative at the lower bound of the velocity range compared with the range of the velocity derived from the method of the composite Lyapunov function. By calculating the hydrodynamic coefficients of the Petrel-II hybrid-driven underwater glider, the simulation analysis has been conducted. In addition, the results of the field trials conducted in the South China Sea and the Danjiangkou Reservoir of China have been presented to illustrate the validity of the analysis and simulation, and to show the feasibility of the method of the composite Lyapunov function which verifies the stability of the Petrel-II hybrid-driven underwater glider.

  9. Burnable absorber coated nuclear fuel

    International Nuclear Information System (INIS)

    Chubb, W.; Radford, K.C.; Parks, B.H.

    1984-01-01

    A nuclear fuel body which is at least partially covered by a burnable neutron absorber layer is provided with a hydrophobic overcoat generally covering the burnable absorber layer and bonded directly to it. In a method for providing a UO 2 fuel pellet with a zirconium diboride burnable poison layer, the fuel body is provided with an intermediate niobium layer. (author)

  10. Metal-shearing energy absorber

    Science.gov (United States)

    Fay, R. J.; Wittrock, E. P.

    1971-01-01

    Device, consisting of tongue of thin aluminum alloy strip, pull tab, slotted steel plate which serves as cutter, and steel buckle, absorbs mechanical energy when its ends are subjected to tensile loading. Device is applicable as auxiliary shock absorbing anchor for automobile and airplane safety belts.

  11. Leaf absorbance and photosynthesis

    Science.gov (United States)

    Schurer, Kees

    1994-01-01

    The absorption spectrum of a leaf is often thought to contain some clues to the photosynthetic action spectrum of chlorophyll. Of course, absorption of photons is needed for photosynthesis, but the reverse, photosynthesis when there is absorption, is not necessarily true. As a check on the existence of absorption limits we measured spectra for a few different leaves. Two techniques for measuring absorption have been used, viz. the separate determination of the diffuse reflectance and the diffuse transmittance with the leaf at a port of an integrating sphere and the direct determination of the non-absorbed fraction with the leaf in the sphere. In a cross-check both methods yielded the same results for the absorption spectrum. The spectrum of a Fuchsia leaf, covering the short-wave region from 350 to 2500 nm, shows a high absorption in UV, blue and red, the well known dip in the green and a steep fall-off at 700 nm. Absorption drops to virtually zero in the near infrared, with subsequent absorptions, corresponding to the water absorption bands. In more detailed spectra, taken at 5 nm intervals with a 5 nm bandwidth, differences in chlorophyll content show in the different depths of the dip around 550 nm and in a small shift of the absorption edge at 700 nm. Spectra for Geranium (Pelargonium zonale) and Hibiscus (with a higher chlorophyll content) show that the upper limit for photosynthesis can not be much above 700 nm. No evidence, however, is to be seen of a lower limit for photosynthesis and, in fact, some experiments down to 300 nm still did not show a decrease of the absorption although it is well recognized that no photosynthesis results with 300 nm wavelengths.

  12. Visible light broadband perfect absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Jia, X. L.; Meng, Q. X.; Yuan, C. X.; Zhou, Z. X.; Wang, X. O., E-mail: wxo@hit.edu.cn [School of Science, Harbin Institute of Technology, Harbin 150001 (China)

    2016-03-15

    The visible light broadband perfect absorbers based on the silver (Ag) nano elliptical disks and holes array are studied using finite difference time domain simulations. The semiconducting indium silicon dioxide thin film is introduced as the space layer in this sandwiched structure. Utilizing the asymmetrical geometry of the structures, polarization sensitivity for transverse electric wave (TE)/transverse magnetic wave (TM) and left circular polarization wave (LCP)/right circular polarization wave (RCP) of the broadband absorption are gained. The absorbers with Ag nano disks and holes array show several peaks absorbance of 100% by numerical simulation. These simple and flexible perfect absorbers are particularly desirable for various potential applications including the solar energy absorber.

  13. An underwater robot controls water tanks in nuclear power plants

    International Nuclear Information System (INIS)

    Lardiere, C.

    2015-01-01

    The enterprises Newton Research Labs and IHI Southwest Technologies have developed a robot equipped with sensors to inspect the inside walls (partially) and bottom of water tanks without being obliged to empty them. The robot called 'Inspector' is made up of 4 main components: a chassis with 4 independent steering wheels, a camera video system able to provide a 360 degree view, various non-destructive testing devices such as underwater laser scanners, automated ultra-sound or Foucault current probes and an operation system for both driving the robot and controlling the testing. The Inspector robot has been used to inspect the inside bottom of an operating condensate tank at the Palo Verde nuclear station. The robot was able to check all the welds joining the bottom plates and the welds between the walls and the bottom. The robot is also able to come back to the exact place where a defect was detected during a previous inspection. (A.C.)

  14. Upper limb joint forces and moments during underwater cyclical movements.

    Science.gov (United States)

    Lauer, Jessy; Rouard, Annie Hélène; Vilas-Boas, João Paulo

    2016-10-03

    Sound inverse dynamics modeling is lacking in aquatic locomotion research because of the difficulty in measuring hydrodynamic forces in dynamic conditions. Here we report the successful implementation and validation of an innovative methodology crossing new computational fluid dynamics and inverse dynamics techniques to quantify upper limb joint forces and moments while moving in water. Upper limb kinematics of seven male swimmers sculling while ballasted with 4kg was recorded through underwater motion capture. Together with body scans, segment inertial properties, and hydrodynamic resistances computed from a unique dynamic mesh algorithm capable to handle large body deformations, these data were fed into an inverse dynamics model to solve for joint kinetics. Simulation validity was assessed by comparing the impulse produced by the arms, calculated by integrating vertical forces over a stroke period, to the net theoretical impulse of buoyancy and ballast forces. A resulting gap of 1.2±3.5% provided confidence in the results. Upper limb joint load was within 5% of swimmer׳s body weight, which tends to supports the use of low-load aquatic exercises to reduce joint stress. We expect this significant methodological improvement to pave the way towards deeper insights into the mechanics of aquatic movement and the establishment of practice guidelines in rehabilitation, fitness or swimming performance. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Urban Sound Ecologies

    DEFF Research Database (Denmark)

    Groth, Sanne Krogh; Samson, Kristine

    2013-01-01

    Within recent years, there has been a renewed focus on sound in urban environments. From sound installations in public space to sound festivals in alternative settings, we find a common interest in sound art relating to the urban environment. Artworks or interventions presented in such contexts s...

  16. Sound reproduction system

    NARCIS (Netherlands)

    Boone, M.M.; De Vries, D.; Horbach, U.

    2002-01-01

    Arrangement of a sound reproduction system (1), including at least one input (2), a sound field generator (4), a loudspeaker panel (10); the at least one input (2) connected to the sound filed generator (4), and the sound filed (4) connected to the loudspeaker panel (10); the at least one input (2)

  17. The Sound of Science

    Science.gov (United States)

    Merwade, Venkatesh; Eichinger, David; Harriger, Bradley; Doherty, Erin; Habben, Ryan

    2014-01-01

    While the science of sound can be taught by explaining the concept of sound waves and vibrations, the authors of this article focused their efforts on creating a more engaging way to teach the science of sound--through engineering design. In this article they share the experience of teaching sound to third graders through an engineering challenge…

  18. Underwater videography and photography in Gulf of Kachchh. Sponsored by Gujarat Ecological Society, Vadodara, Gujarat

    Digital Repository Service at National Institute of Oceanography (India)

    Marine Archaeology Centre (MAC) has been carrying out underwater explorations and excavations of ancient ports and sunken shipwrecks to preserve underwater cultural heritage. MAC has the infrastructure facility to carry out underwater investigations...

  19. Hydrodynamic Coefficients Identification and Experimental Investigation for an Underwater Vehicle

    Directory of Open Access Journals (Sweden)

    Shaorong XIE

    2014-02-01

    Full Text Available Hydrodynamic coefficients are the foundation of unmanned underwater vehicles modeling and controller design. In order to reduce identification complexity and acquire necessary hydrodynamic coefficients for controllers design, the motion of the unmanned underwater vehicle was separated into vertical motion and horizontal motion models. Hydrodynamic coefficients were regarded as mapping parameters from input forces and moments to output velocities and acceleration of the unmanned underwater vehicle. The motion models of the unmanned underwater vehicle were nonlinear and Genetic Algorithm was adopted to identify those hydrodynamic coefficients. To verify the identification quality, velocities and acceleration of the unmanned underwater vehicle was measured using inertial sensor under the same conditions as Genetic Algorithm identification. Curves similarity between measured velocities and acceleration and those identified by Genetic Algorithm were used as optimizing standard. It is found that the curves similarity were high and identified hydrodynamic coefficients of the unmanned underwater vehicle satisfied the measured motion states well.

  20. Delay Tolerance in Underwater Wireless Communications: A Routing Perspective

    Directory of Open Access Journals (Sweden)

    Safdar Hussain Bouk

    2016-01-01

    Full Text Available Similar to terrestrial networks, underwater wireless networks (UWNs also aid several critical tasks including coastal surveillance, underwater pollution detection, and other maritime applications. Currently, once underwater sensor nodes are deployed at different levels of the sea, it is nearly impossible or very expensive to reconfigure the hardware, for example, battery. Taking this issue into account, considerable amount of research has been carried out to ensure minimum energy costs and reliable communication between underwater nodes and base stations. As a result, several different network protocols were proposed for UWN, including MAC, PHY, transport, and routing. Recently, a new paradigm was introduced claiming that the intermittent nature of acoustic channel and signal resulted in designing delay tolerant routing schemes for the UWN, known as an underwater delay tolerant network. In this paper, we provide a comprehensive survey of underwater routing protocols with emphasis on the limitations, challenges, and future open issues in the context of delay tolerant network routing.

  1. Optimization on microlattice materials for sound absorption by an integrated transfer matrix method.

    Science.gov (United States)

    Cai, Xiaobing; Yang, Jun; Hu, Gengkai

    2015-04-01

    Materials with well-defined microlattice structures are superlight, stable, and thus bear great potential in sound absorption. An integrated transfer matrix method (TMM) is proposed to evaluate the sound absorbing efficiency of these lattice materials, in which a massive number of micropores are densely placed. A comparison between integrated TMM and conventional TMM reveals that the proposed approach offers better predictions on sound absorption of microlattice. This approach is then employed to optimize the microlattice material to determine the best pore and porosity that lead to maximum absorbing efficiency capability and minimum required thickness to attain a target sound absorption.

  2. An Evaluation of Potential Operating Systems for Autonomous Underwater Vehicles

    Science.gov (United States)

    2013-02-01

    remote control of such vehicles requires the use of a tether , limiting the vehicle’s range; however operating underwater vehicles autonomously requires...URBI Universal Robot Body Interface UUV Unmanned Underwater Vehicle UNCLASSIFIED xi DSTO–TN–1194 UNCLASSIFIED THIS PAGE IS INTENTIONALLY BLANK xii... underwater environment, where many platforms are still reliant upon an umbilical tether for power and high bandwidth communications. This tether

  3. On the Performance of the Underwater Acoustic Sensor Networks

    Science.gov (United States)

    2015-05-01

    waves for Underwater Wireless Communication (UWC); radio waves, optical waves, and acoustic waves are few to name. Radio waves are good for extra low...2211 underwater communication , wireless sensors, mutual information REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR...Cotae, “On the Performance of the Underwater Wireless Communication Sensor Networks: Work in Progress” ASEE Mid-Atlantic Fall 2014 Conference

  4. Underwater laser beam welding of Alloy 690

    International Nuclear Information System (INIS)

    Hino, Takehisa; Tamura, Masataka; Kono, Wataru; Kawano, Shohei; Yoda, Masaki

    2009-01-01

    Stress Corrosion Clacking (SCC) has been reported at Alloy 600 welds between nozzles and safe-end in Pressurized Water Reactor (PWR) plant. Alloy 690, which has higher chromium content than Alloy 600, has been applied for cladding on Alloy 600 welds for repairing damaged SCC area. Toshiba has developed Underwater Laser Beam Welding technique. This method can be conducted without draining, so that the repairing period and the radiation exposure during the repair can be dramatically decreased. In some old PWRs, high-sulfur stainless steel is used as the materials for this section. It has a high susceptibility of weld cracks. Therefore, the optimum welding condition of Alloy 690 on the high-sulfur stainless steel was investigated with our Underwater Laser Beam Welding unit. Good cladding layer, without any crack, porosity or lack of fusion, could be obtained. (author)

  5. Underwater noise modelling for environmental impact assessment

    Energy Technology Data Exchange (ETDEWEB)

    Farcas, Adrian [Centre for Environment, Fisheries and Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT (United Kingdom); Thompson, Paul M. [Lighthouse Field Station, Institute of Biological and Environmental Sciences, University of Aberdeen, Cromarty IV11 8YL (United Kingdom); Merchant, Nathan D., E-mail: nathan.merchant@cefas.co.uk [Centre for Environment, Fisheries and Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT (United Kingdom)

    2016-02-15

    Assessment of underwater noise is increasingly required by regulators of development projects in marine and freshwater habitats, and noise pollution can be a constraining factor in the consenting process. Noise levels arising from the proposed activity are modelled and the potential impact on species of interest within the affected area is then evaluated. Although there is considerable uncertainty in the relationship between noise levels and impacts on aquatic species, the science underlying noise modelling is well understood. Nevertheless, many environmental impact assessments (EIAs) do not reflect best practice, and stakeholders and decision makers in the EIA process are often unfamiliar with the concepts and terminology that are integral to interpreting noise exposure predictions. In this paper, we review the process of underwater noise modelling and explore the factors affecting predictions of noise exposure. Finally, we illustrate the consequences of errors and uncertainties in noise modelling, and discuss future research needs to reduce uncertainty in noise assessments.

  6. Ocean Research Enabled by Underwater Gliders

    Science.gov (United States)

    Rudnick, Daniel L.

    2016-01-01

    Underwater gliders are autonomous underwater vehicles that profile vertically by changing their buoyancy and use wings to move horizontally. Gliders are useful for sustained observation at relatively fine horizontal scales, especially to connect the coastal and open ocean. In this review, research topics are grouped by time and length scales. Large-scale topics addressed include the eastern and western boundary currents and the regional effects of climate variability. The accessibility of horizontal length scales of order 1 km allows investigation of mesoscale and submesoscale features such as fronts and eddies. Because the submesoscales dominate vertical fluxes in the ocean, gliders have found application in studies of biogeochemical processes. At the finest scales, gliders have been used to measure internal waves and turbulent dissipation. The review summarizes gliders' achievements to date and assesses their future in ocean observation.

  7. Little Sounds

    Directory of Open Access Journals (Sweden)

    Baker M. Bani-Khair

    2017-10-01

    Full Text Available The Spider and the Fly   You little spider, To death you aspire... Or seeking a web wider, To death all walking, No escape you all fighters… Weak and fragile in shape and might, Whatever you see in the horizon, That is destiny whatever sight. And tomorrow the spring comes, And the flowers bloom, And the grasshopper leaps high, And the frogs happily cry, And the flies smile nearby, To that end, The spider has a plot, To catch the flies by his net, A mosquito has fallen down in his net, Begging him to set her free, Out of that prison, To her freedom she aspires, Begging...Imploring...crying,  That is all what she requires, But the spider vows never let her free, His power he admires, Turning blind to light, And with his teeth he shall bite, Leaving her in desperate might, Unable to move from site to site, Tied up with strings in white, Wrapped up like a dead man, Waiting for his grave at night,   The mosquito says, Oh little spider, A stronger you are than me in power, But listen to my words before death hour, Today is mine and tomorrow is yours, No escape from death... Whatever the color of your flower…     Little sounds The Ant The ant is a little creature with a ferocious soul, Looking and looking for more and more, You can simply crush it like dead mold, Or you can simply leave it alone, I wonder how strong and strong they are! Working day and night in a small hole, Their motto is work or whatever you call… A big boon they have and joy in fall, Because they found what they store, A lesson to learn and memorize all in all, Work is something that you should not ignore!   The butterfly: I’m the butterfly Beautiful like a blue clear sky, Or sometimes look like snow, Different in colors, shapes and might, But something to know that we always die, So fragile, weak and thin, Lighter than a glimpse and delicate as light, Something to know for sure… Whatever you have in life and all these fields, You are not happier than a butterfly

  8. A MAC protocol for underwater sensors networks

    OpenAIRE

    Santos, Rodrigo; Orozco, Javier; Ochoa, Sergio; Meseguer Pallarès, Roc; Eggly, Gabriel

    2015-01-01

    “The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-26401-1_37." Underwater sensor networks are becoming an important field of research, because of its everyday increasing application scope. Examples of their application areas are environmental and pollution monitoring (mainly oil spills), oceanographic data collection, support for submarine geo-localization, ocean sampling and early tsunamis alert. It is well-known the challenge that represents to perfo...

  9. Passive Mode Carbon Nanotube Underwater Acoustic Transducer

    Science.gov (United States)

    2016-09-20

    irreversible Joule heat) by an electric light bulb . The reciprocal (or reverse) of this process by supplying heat and shining light to the same electric bulb ...limit the invention to the precise form disclosed; and obviously many modifications and variations are possible in light of the above teaching...300151 1 of 14 PASSIVE MODE CARBON NANOTUBE UNDERWATER ACOUSTIC TRANSDUCER STATEMENT OF GOVERNMENT INTEREST [0001] The invention described

  10. Underwater suction device for irradiated materials

    International Nuclear Information System (INIS)

    Qurnell, F.D.; Peloquin, A.V.

    1982-01-01

    An underwater suction device for collecting irradiated materials in a pool of water includes injection and suction tubes and a removable, disposable filter for capturing irradiated materials. Pressurized water is injected into the suction tube through a jet pump nozzle to establish a suction flow through the tube. The suction device is manoeuverable by a pole, which is pivotally connected to the suction device by a latching mechanism. (author)

  11. Tethered Antennas for Unmanned Underwater Vehicles

    Science.gov (United States)

    2009-04-27

    Concepts The first design (Figure 1) was based on the concept of an airfoil kite. The shape of the tow body was built around a NACA5515 hydrofoil to...Underwater Vehicles Brooke Ocean Technology (USA) Inc. 6 Figure 1: Hydrofoil Design The second design was based on that of a boat hull...communications. A sharp bow was utilized to cut through the water to reduce drag when on the surface. Like the hydrofoil design the top profile was

  12. MEDITERRANEAN: Underwater neutrinos get off the ground

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    Now funded is the initial stage of NESTOR, an imaginative new programme for a dedicated underwater neutrino astroparticle physics laboratory. Located in the international waters off the southernmost corner of continental Europe near the town of Pylos in S.W. Greece, NESTOR (NEutrinos from Supernovae and TeV sources Ocean Range) recalls the wise king of Pylos who counselled the Greeks during the Trojan war, an excellent tradition for new scientific goals of detecting neutrinos

  13. Role of Confined Water in Underwater Adhesion

    Science.gov (United States)

    Dhinojwala, Ali

    Surface bound water is a strong deterrent for forming strong bonds between two surfaces underwater and expelling that bound water is important for strong adhesion. I will discuss examples of different strategies used by geckos, spiders, and mussels to handle this last layer of bound water. Recent results using infrared-visible sum frequency generation spectroscopy to probe the structure of this bound water will be discussed. National Science Foundation.

  14. Obstacle avoidance in underwater glider path planning

    OpenAIRE

    Isern González, Josep; Hernández Sosa, Daniel; Fernández Perdomo, Enrique; Cabrera Gámez, Jorge; Domínguez Brito, Antonio Carlos; Prieto Marañón, Víctor

    2012-01-01

    Underwater gliders have revealed as a valuable scientific platform, with a growing number of successful environmental sampling applications. They are specially suited for long range missions due to their unmatched autonomy level, although their low surge speed make them strongly affected by ocean currents. Path planning constitute a real concern for this type of vehicle, as it may reduce the time taken to reach a given waypoint or save power. In such a dynamic environment it is not easy to fi...

  15. A Recovery System for Unmanned Underwater Vehicles

    Science.gov (United States)

    2017-09-28

    300170 1 of 10 A RECOVERY SYSTEM FOR UNMANNED UNDERWATER VEHICLES STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may...6 of 10 forces cannot be easily predicted and can be strong enough to require a significantly larger handling system and significantly more...the sea state, the ship handling system , the capture mechanism and the design of the capture mechanism 400. [0024] The water jets 100 will increase

  16. Reef Sound as an Orientation Cue for Shoreward Migration by Pueruli of the Rock Lobster, Jasus edwardsii.

    Science.gov (United States)

    Hinojosa, Ivan A; Green, Bridget S; Gardner, Caleb; Hesse, Jan; Stanley, Jenni A; Jeffs, Andrew G

    2016-01-01

    The post-larval or puerulus stage of spiny, or rock, lobsters (Palinuridae) swim many kilometres from open oceans into coastal waters where they subsequently settle. The orientation cues used by the puerulus for this migration are unclear, but are presumed to be critical to finding a place to settle. Understanding this process may help explain the biological processes of dispersal and settlement, and be useful for developing realistic dispersal models. In this study, we examined the use of reef sound as an orientation cue by the puerulus stage of the southern rock lobster, Jasus edwardsii. Experiments were conducted using in situ binary choice chambers together with replayed recording of underwater reef sound. The experiment was conducted in a sandy lagoon under varying wind conditions. A significant proportion of puerulus (69%) swam towards the reef sound in calm wind conditions. However, in windy conditions (>25 m s-1) the orientation behaviour appeared to be less consistent with the inclusion of these results, reducing the overall proportion of pueruli that swam towards the reef sound (59.3%). These results resolve previous speculation that underwater reef sound is used as an orientation cue in the shoreward migration of the puerulus of spiny lobsters, and suggest that sea surface winds may moderate the ability of migrating pueruli to use this cue to locate coastal reef habitat to settle. Underwater sound may increase the chance of successful settlement and survival of this valuable species.

  17. Research on Operational Aspects of Large Autonomous Underwater Glider Fleets

    National Research Council Canada - National Science Library

    Fratantoni, David M

    2007-01-01

    This program supported research on the operational and management issues stemming from application of large fleets of autonomous underwater gliders to oceanographic research and rapid environmental...

  18. Underwater hearing in the great cormorant (Phalacrocorax carbo sinensis)

    DEFF Research Database (Denmark)

    Hansen, Kirstin Anderson; Larsen, Ole Næsbye; Wahlberg, Magnus

    2016-01-01

    The underwater hearing threshold of a great cormorant (Phalacrocroax carbo sinensis) was measured at 2 kHz using psychophysical methods. Previous in-air and underwater testing suggests that cormorants have rather poor in-air hearing compared to other birds of similar size (Johansen, 2016). Prelim......The underwater hearing threshold of a great cormorant (Phalacrocroax carbo sinensis) was measured at 2 kHz using psychophysical methods. Previous in-air and underwater testing suggests that cormorants have rather poor in-air hearing compared to other birds of similar size (Johansen, 2016...

  19. Calibration Techniques for Accurate Measurements by Underwater Camera Systems.

    Science.gov (United States)

    Shortis, Mark

    2015-12-07

    Calibration of a camera system is essential to ensure that image measurements result in accurate estimates of locations and dimensions within the object space. In the underwater environment, the calibration must implicitly or explicitly model and compensate for the refractive effects of waterproof housings and the water medium. This paper reviews the different approaches to the calibration of underwater camera systems in theoretical and practical terms. The accuracy, reliability, validation and stability of underwater camera system calibration are also discussed. Samples of results from published reports are provided to demonstrate the range of possible accuracies for the measurements produced by underwater camera systems.

  20. Calibration Techniques for Accurate Measurements by Underwater Camera Systems

    Directory of Open Access Journals (Sweden)

    Mark Shortis

    2015-12-01

    Full Text Available Calibration of a camera system is essential to ensure that image measurements result in accurate estimates of locations and dimensions within the object space. In the underwater environment, the calibration must implicitly or explicitly model and compensate for the refractive effects of waterproof housings and the water medium. This paper reviews the different approaches to the calibration of underwater camera systems in theoretical and practical terms. The accuracy, reliability, validation and stability of underwater camera system calibration are also discussed. Samples of results from published reports are provided to demonstrate the range of possible accuracies for the measurements produced by underwater camera systems.

  1. Automatic stabilization of underwater robots in the time manipulation operations

    International Nuclear Information System (INIS)

    Filaretov, V.F.; Koval, E.V.

    1994-01-01

    When carrying out underwater technical works by means of an underwater vehicles having a manipulator it is desirable to perform manipulation operations in the regime of the underwater vehicle hovering above the object without durable and complicated operations up its rigid fixation. Underwater vehicle stabilization is achieved by compensation all the effects on the vehicle caused by the operating manipulator in water medium. This automatic stabilization is formed due to input of the required control signals into corresponding vehicle propellers proportional to calculated components of the generalized forces and moments. The propellers should form stops reacting against effects

  2. Contour Tracking Control for the REMUS Autonomous Underwater Vehicle

    National Research Council Canada - National Science Library

    Van Reet, Alan R

    2005-01-01

    In the interest of enhancing the capabilities of autonomous underwater vehicles used in US Naval Operations, controlling vehicle position to follow depth contours presents exciting potential for navigation...

  3. Autopilot Using Differential Thrust for ARIES Autonomous Underwater Vehicle

    National Research Council Canada - National Science Library

    Sarton, Christopher

    2003-01-01

    .... Unfortunately, communication antennas must point to specific satellites in this system and thus underwater vehicles must steer a specific course on the surface during the communication process...

  4. Do top predators cue on sound production by mesopelagic prey?

    Science.gov (United States)

    Baumann-Pickering, S.; Checkley, D. M., Jr.; Demer, D. A.

    2016-02-01

    Deep-scattering layer (DSL) organisms, comprising a variety of mesopelagic fishes, and squids, siphonophores, crustaceans, and other invertebrates, are preferred prey for numerous large marine predators, e.g. cetaceans, seabirds, and fishes. Some of the DSL species migrate from depth during daylight to feed near the surface at night, transitioning during dusk and dawn. We investigated if any DSL organisms create sound, particularly during the crepuscular periods. Over several nights in summer 2015, underwater sound was recorded in the San Diego Trough using a high-frequency acoustic recording package (HARP, 10 Hz to 100 kHz), suspended from a drifting surface float. Acoustic backscatter from the DSL was monitored nearby using a calibrated multiple-frequency (38, 70, 120, and 200 kHz) split-beam echosounder (Simrad EK60) on a small boat. DSL organisms produced sound, between 300 and 1000 Hz, and the received levels were highest when the animals migrated past the recorder during ascent and descent. The DSL are globally present, so the observed acoustic phenomenon, if also ubiquitous, has wide-reaching implications. Sound travels farther than light or chemicals and thus can be sensed at greater distances by predators, prey, and mates. If sound is a characteristic feature of pelagic ecosystems, it likely plays a role in predator-prey relationships and overall ecosystem dynamics. Our new finding inspires numerous questions such as: Which, how, and why have DSL organisms evolved to create sound, for what do they use it and under what circumstances? Is sound production by DSL organisms truly ubiquitous, or does it depend on the local environment and species composition? How may sound production and perception be adapted to a changing environment? Do predators react to changes in sound? Can sound be used to quantify the composition of mixed-species assemblages, component densities and abundances, and hence be used in stock assessment or predictive modeling?

  5. Underwater Acoustic Target Tracking: A Review.

    Science.gov (United States)

    Luo, Junhai; Han, Ying; Fan, Liying

    2018-01-02

    Advances in acoustic technology and instrumentation now make it possible to explore marine resources. As a significant component of ocean exploration, underwater acoustic target tracking has aroused wide attention both in military and civil fields. Due to the complexity of the marine environment, numerous techniques have been proposed to obtain better tracking performance. In this paper, we survey over 100 papers ranging from innovative papers to the state-of-the-art in this field to present underwater tracking technologies. Not only the related knowledge of acoustic tracking instrument and tracking progress is clarified in detail, but also a novel taxonomy method is proposed. In this paper, algorithms for underwater acoustic target tracking are classified based on the methods used as: (1) instrument-assisted methods; (2) mode-based methods; (3) tracking optimization methods. These algorithms are compared and analyzed in the aspect of dimensions, numbers, and maneuvering of the tracking target, which is different from other survey papers. Meanwhile, challenges, countermeasures, and lessons learned are illustrated in this paper.

  6. Modeling and Control of Underwater Robotic Systems

    Energy Technology Data Exchange (ETDEWEB)

    Schjoelberg, I:

    1996-12-31

    This doctoral thesis describes modeling and control of underwater vehicle-manipulator systems. The thesis also presents a model and a control scheme for a system consisting of a surface vessel connected to an underwater robotic system by means of a slender marine structure. The equations of motion of the underwater vehicle and manipulator are described and the system kinematics and properties presented. Feedback linearization technique is applied to the system and evaluated through a simulation study. Passivity-based controllers for vehicle and manipulator control are presented. Stability of the closed loop system is proved and simulation results are given. The equation of motion for lateral motion of a cable/riser system connected to a surface vessel at the top end and to a thruster at the bottom end is described and stability analysis and simulations are presented. The equations of motion in 3 degrees of freedom of the cable/riser, surface vessel and robotic system are given. Stability analysis of the total system with PD-controllers is presented. 47 refs., 32 figs., 7 tabs.

  7. Sound absorption of a finite micro-perforated panel backed by a shunted loudspeaker.

    Science.gov (United States)

    Tao, Jiancheng; Jing, Ruixiang; Qiu, Xiaojun

    2014-01-01

    Deep back cavities are usually required for micro-perforated panel (MPP) constructions to achieve good low frequency absorption. To overcome the problem, a close-box loudspeaker with a shunted circuit is proposed to substitute the back wall of the cavity of the MPP constructions to constitute a composite absorber. Based on the equivalent circuit model, the acoustic impedance of the shunted loudspeaker is formulated first, then a prediction model of the sound absorption of the MPP backed by shunted loudspeaker is developed by employing the mode solution of a finite size MPP coupled by an air cavity with an impendence back wall. The MPP absorbs mid to high frequency sound, and with properly adjusted electrical parameters of its shunted circuit, the shunted loudspeaker absorbs low frequency sound, so the composite absorber provides a compact solution to broadband sound control. Numerical simulations and experiments are carried out to validate the model.

  8. Fractal Model for Acoustic Absorbing of Porous Fibrous Metal Materials

    Directory of Open Access Journals (Sweden)

    Weihua Chen

    2016-01-01

    Full Text Available To investigate the changing rules between sound absorbing performance and geometrical parameters of porous fibrous metal materials (PFMMs, this paper presents a fractal acoustic model by incorporating the static flow resistivity based on Biot-Allard model. Static flow resistivity is essential for an accurate assessment of the acoustic performance of the PFMM. However, it is quite difficult to evaluate the static flow resistivity from the microstructure of the PFMM because of a large number of disordered pores. In order to overcome this difficulty, we firstly established a static flow resistivity formula for the PFMM based on fractal theory. Secondly, a fractal acoustic model was derived on the basis of the static flow resistivity formula. The sound absorption coefficients calculated by the presented acoustic model were validated by the values of Biot-Allard model and experimental data. Finally, the variation of the surface acoustic impedance, the complex wave number, and the sound absorption coefficient with the fractal dimensions were discussed. The research results can reveal the relationship between sound absorption and geometrical parameters and provide a basis for improving the sound absorption capability of the PFMMs.

  9. Synthesized size-sound sound symbolism

    NARCIS (Netherlands)

    Lockwood, G.F.; Hagoort, P.; Dingemanse, M.; Papafragou, A.; Grodner, D.; Mirman, D.; Trueswell, J.

    2016-01-01

    Studies of sound symbolism have shown that people can associate sound and meaning in consistent ways when presented with maximally contrastive stimulus pairs of nonwords such as bouba/kiki (rounded/sharp) or mil/mal (small/big). Recent work has shown the effect extends to antonymic words from

  10. A composite of borohydride and super absorbent polymer for hydrogen generation

    Science.gov (United States)

    Li, Z. P.; Liu, B. H.; Liu, F. F.; Xu, D.

    To develop a hydrogen source for underwater applications, a composite of sodium borohydride and super absorbent polymer (SAP) is prepared by ball milling sodium borohydride powder with SAP powder, and by dehydrating an alkaline borohydride gel. When sodium polyacrylate (NaPAA) is used as the SAP, the resulting composite exhibits a high rate of borohydride hydrolysis for hydrogen generation. A mechanism of hydrogen evolution from the NaBH 4-NaPAA composite is suggested based on structure analysis by X-ray diffraction and scanning electron microscopy. The effects of water and NiCl 2 content in the precursor solution on the hydrogen evolution behavior are investigated and discussed.

  11. Near-field and high-resolution cylindrical noise source location method based on vector sound pressure array

    Directory of Open Access Journals (Sweden)

    ZUO Xiang

    2017-08-01

    Full Text Available The existing underwater noise source near-field location method usually assumes that the measurement plane is flat, which increases the difficulty of applying the underwater noise target test for cylindrical distribution. Simultaneously, the conventional near-field focused beam has a lower spatial resolution when used to locate an underwater noise source with cylindrical distribution. Moreover, the near-field underwater noise source location method based on the sound pressure array has a left and right side fuzzy problem. In order to solve these problems, by establishing the near-field measurement model of the noise source with cylindrical distribution as the measurement surface, and combining the unilateral directivity of the vector hydrophone and the high resolution characteristics of the MUSIC algorithm, a near-field and high resolution location method is proposed for cylindrical distribution based on vector sound pressure, and a computer simulation is carried out. The results show that the method can use a smaller array aperture to locate the underwater noise source, enabling it to be used to locate and recognize the noise sources of complex and large-scale cylindrical systems.

  12. Making fictions sound real

    DEFF Research Database (Denmark)

    Langkjær, Birger

    2010-01-01

    of sounds. Apart from an account of the kinds of sounds that typically appear in a specific genre, a genre analysis of sound may also benefit from a functionalist approach that focuses on how sounds can make both realist and non-realist aspects of genres sound real to audiences.......This article examines the role that sound plays in making fictions perceptually real to film audiences, whether these fictions are realist or non-realist in content and narrative form. I will argue that some aspects of film sound practices and the kind of experiences they trigger are related...... to basic rules of human perception, whereas others are more properly explained in relation to how aesthetic devices, including sound, are used to characterise the fiction and thereby make it perceptually real to its audience. Finally, I will argue that not all genres can be defined by a simple taxonomy...

  13. Making fictions sound real

    DEFF Research Database (Denmark)

    Langkjær, Birger

    2010-01-01

    This article examines the role that sound plays in making fictions perceptually real to film audiences, whether these fictions are realist or non-realist in content and narrative form. I will argue that some aspects of film sound practices and the kind of experiences they trigger are related...... to basic rules of human perception, whereas others are more properly explained in relation to how aesthetic devices, including sound, are used to characterise the fiction and thereby make it perceptually real to its audience. Finally, I will argue that not all genres can be defined by a simple taxonomy...... of sounds. Apart from an account of the kinds of sounds that typically appear in a specific genre, a genre analysis of sound may also benefit from a functionalist approach that focuses on how sounds can make both realist and non-realist aspects of genres sound real to audiences....

  14. Sound wave transmission (image)

    Science.gov (United States)

    When sounds waves reach the ear, they are translated into nerve impulses. These impulses then travel to the brain where they are interpreted by the brain as sound. The hearing mechanisms within the inner ear, can ...

  15. Absorber materials in CANDU PHWR's

    International Nuclear Information System (INIS)

    Price, E.G.; Boss, C.R.; Novak, W.Z.; Fong, R.W.L.

    1995-03-01

    In a CANDU reactor the fuel channels are arranged on a square lattice in a calandria filled with heavy water moderator. This arrangement allows five types of tubular neutron absorber devices to be located in a relatively benign environment of low pressure, low temperature heavy water between neighbouring rows of columns of fuel channels. This paper will describe the roles of the devices and outline the design requirements of the absorber component from a reactor physics viewpoint. Nuclear heating and activation problems associated with the different absorbers will be briefly discussed. The design and manufacture of the devices will be also discussed. The control rod absorbers and shut off materials are cadmium and stainless steel. In the tubular arrangement, the cadmium is sandwiched between stainless steel tubes. This type of device has functioned well, but there is now concern over the availability and expense of cadmium which is used in two types of CANDU control devices. There are also concerns about the toxicity of cadmium during the fabrication of the absorbers. These concerns are prompting AECL to study alternatives. To minimize design changes, pure boron-10 alloyed in stainless steel is a favoured option. Work is underway to confirm the suitability of the boron-loaded steel and identify other encapsulated absorber materials for practical application. Because the reactivity devices or their guide tubes span the calandria vessel, the long slender components must be sufficiently rigid to resist operational vibration and also be seismically stable. Some of these components are made of Zircaloy to minimize neutron absorption. Slow irradiation growth and creep can reduce the spring tension, and periodic adjustments to the springs are required. Experience with the control absorber devices has generally been good. In one instance liquid zone controllers had a problem of vibration induced fretting but a designed back-fit resolved the problem. (author). 3 refs., 1

  16. Development of underwater laser cutting technique for steel and ...

    Indian Academy of Sciences (India)

    We have developed underwater cutting technique for 4.2 mm thick zircaloy pressure tubes and up to 6 mm thick steel using fibre-coupled 250 W average power pulsed Nd:YAG laser. This underwater cutting technique will be highly useful in various nuclear applications as well as in dismantling/repair of ship and pipe lines ...

  17. Visual-adaptation-mechanism based underwater object extraction

    Science.gov (United States)

    Chen, Zhe; Wang, Huibin; Xu, Lizhong; Shen, Jie

    2014-03-01

    Due to the major obstacles originating from the strong light absorption and scattering in a dynamic underwater environment, underwater optical information acquisition and processing suffer from effects such as limited range, non-uniform lighting, low contrast, and diminished colors, causing it to become the bottleneck for marine scientific research and projects. After studying and generalizing the underwater biological visual mechanism, we explore its advantages in light adaption which helps animals to precisely sense the underwater scene and recognize their prey or enemies. Then, aiming to transform the significant advantage of the visual adaptation mechanism into underwater computer vision tasks, a novel knowledge-based information weighting fusion model is established for underwater object extraction. With this bionic model, the dynamical adaptability is given to the underwater object extraction task, making them more robust to the variability of the optical properties in different environments. The capability of the proposed method to adapt to the underwater optical environments is shown, and its outperformance for the object extraction is demonstrated by comparison experiments.

  18. Self-localization for underwater inspection robot in reactor systems

    International Nuclear Information System (INIS)

    Kobayashi, Futoshi; Kojima, Fumio

    2007-01-01

    An underwater inspection robot has been needed for preventive maintenance in a nuclear power plant. This paper deals with a self-localization method for the underwater inspection robot. In this method, the position and the orientation of the robot are estimated by using the particle filter. For showing the effectiveness of the proposed method, an experiment with real robot is demonstrated. (author)

  19. Characterization of ships as sources of underwater noise

    NARCIS (Netherlands)

    Jong, C.A.F. de

    2009-01-01

    There is a growing interest in the possible impact of anthropogenic underwater noise on marine life [1]. One of the concerns is the increasing contribution of shipping noise, with the growing number and size of commercial ships. Traditionally, underwater radiated noise control was only of interest

  20. Development of underwater laser cutting technique for steel and ...

    Indian Academy of Sciences (India)

    Laser cutting; underwater laser cutting; fibre optic beam delivery; Nd:YAG laser; material processing; heat affected zone; microstructure. PACS Nos 42.62.Cf; 42.62.-b; 42.55.Rz; 42.81.Ai; 42.81.-i. 1. Introduction. Underwater laser cutting and welding has many applications in nuclear facilities and shiping industry and is a ...

  1. Fish protection at water intakes using a new signal development process and sound system

    International Nuclear Information System (INIS)

    Loeffelman, P.H.; Klinect, D.A.; Van Hassel, J.H.

    1991-01-01

    American Electric Power Company, Inc., is exploring the feasibility of using a patented signal development process and sound system to guide aquatic animals with underwater sound. Sounds from animals such as chinook salmon, steelhead trout, striped bass, freshwater drum, largemouth bass, and gizzard shad can be used to synthesize a new signal to stimulate the animal in the most sensitive portion of its hearing range. AEP's field tests during its research demonstrate that adult chinook salmon, steelhead trout and warmwater fish, and steelhead trout and chinook salmon smolts can be repelled with a properly-tuned system. The signal development process and sound system is designed to be transportable and use animals at the site to incorporate site-specific factors known to affect underwater sound, e.g., bottom shape and type, water current, and temperature. This paper reports that, because the overall goal of this research was to determine the feasibility of using sound to divert fish, it was essential that the approach use a signal development process which could be customized to animals and site conditions at any hydropower plant site

  2. Broadcast sound technology

    CERN Document Server

    Talbot-Smith, Michael

    1990-01-01

    Broadcast Sound Technology provides an explanation of the underlying principles of modern audio technology. Organized into 21 chapters, the book first describes the basic sound; behavior of sound waves; aspects of hearing, harming, and charming the ear; room acoustics; reverberation; microphones; phantom power; loudspeakers; basic stereo; and monitoring of audio signal. Subsequent chapters explore the processing of audio signal, sockets, sound desks, and digital audio. Analogue and digital tape recording and reproduction, as well as noise reduction, are also explained.

  3. An Antropologist of Sound

    DEFF Research Database (Denmark)

    Groth, Sanne Krogh

    2015-01-01

    PROFESSOR PORTRAIT: Sanne Krogh Groth met Holger Schulze, newly appointed professor in Musicology at the Department for Arts and Cultural Studies, University of Copenhagen, to a talk about anthropology of sound, sound studies, musical canons and ideology.......PROFESSOR PORTRAIT: Sanne Krogh Groth met Holger Schulze, newly appointed professor in Musicology at the Department for Arts and Cultural Studies, University of Copenhagen, to a talk about anthropology of sound, sound studies, musical canons and ideology....

  4. Form Follows Sound

    OpenAIRE

    Caramiaux, Baptiste; Altavilla, Alessandro; Pobiner, Scott G.; Tanaka, Atau

    2015-01-01

    Sonic interaction is the continuous relationship between user actions and sound, mediated by some technology. Because interaction with sound may be task oriented or experience-based it is important to understand the nature of action-sound relationships in order to design rich sonic interactions. We propose a participatory approach to sonic interaction design that first considers the affordances of sounds in order to imagine embodied interaction, and based on this, generates interaction models...

  5. Modelling Hyperboloid Sound Scattering

    DEFF Research Database (Denmark)

    Burry, Jane; Davis, Daniel; Peters, Brady

    2011-01-01

    The Responsive Acoustic Surfaces workshop project described here sought new understandings about the interaction between geometry and sound in the arena of sound scattering. This paper reports on the challenges associated with modelling, simulating, fabricating and measuring this phenomenon using...... both physical and digital models at three distinct scales. The results suggest hyperboloid geometry, while difficult to fabricate, facilitates sound scattering....

  6. Abnormal sound detection device

    International Nuclear Information System (INIS)

    Yamada, Izumi; Matsui, Yuji.

    1995-01-01

    Only components synchronized with rotation of pumps are sampled from detected acoustic sounds, to judge the presence or absence of abnormality based on the magnitude of the synchronized components. A synchronized component sampling means can remove resonance sounds and other acoustic sounds generated at a synchronously with the rotation based on the knowledge that generated acoustic components in a normal state are a sort of resonance sounds and are not precisely synchronized with the number of rotation. On the other hand, abnormal sounds of a rotating body are often caused by compulsory force accompanying the rotation as a generation source, and the abnormal sounds can be detected by extracting only the rotation-synchronized components. Since components of normal acoustic sounds generated at present are discriminated from the detected sounds, reduction of the abnormal sounds due to a signal processing can be avoided and, as a result, abnormal sound detection sensitivity can be improved. Further, since it is adapted to discriminate the occurrence of the abnormal sound from the actually detected sounds, the other frequency components which are forecast but not generated actually are not removed, so that it is further effective for the improvement of detection sensitivity. (N.H.)

  7. Capacitive Micromachined Ultrasonic Transducers (CMUTs for Underwater Imaging Applications

    Directory of Open Access Journals (Sweden)

    Jinlong Song

    2015-09-01

    Full Text Available A capacitive micromachined ultrasonic transducer structure for use in underwater imaging is designed, fabricated and tested in this paper. In this structure, a silicon dioxide insulation layer is inserted between the top electrodes and the vibration membrane to prevent ohmic contact. The capacitance-voltage (C-V characteristic curve shows that the transducer offers suitable levels of hysteresis and repeatability performance. The −6 dB center frequency is 540 kHz and the transducer has a bandwidth of 840 kHz for a relative bandwidth of 155%. Underwater pressure of 143.43 Pa is achieved 1 m away from the capacitive micromachined ultrasonic transducer under 20  excitation. Two-dimensional underwater ultrasonic imaging, which is able to prove that a rectangular object is present underwater, is achieved. The results presented here indicate that our work will be highly beneficial for the establishment of an underwater ultrasonic imaging system.

  8. Underwater Sensor Network Redeployment Algorithm Based on Wolf Search.

    Science.gov (United States)

    Jiang, Peng; Feng, Yang; Wu, Feng

    2016-10-21

    This study addresses the optimization of node redeployment coverage in underwater wireless sensor networks. Given that nodes could easily become invalid under a poor environment and the large scale of underwater wireless sensor networks, an underwater sensor network redeployment algorithm was developed based on wolf search. This study is to apply the wolf search algorithm combined with crowded degree control in the deployment of underwater wireless sensor networks. The proposed algorithm uses nodes to ensure coverage of the events, and it avoids the prematurity of the nodes. The algorithm has good coverage effects. In addition, considering that obstacles exist in the underwater environment, nodes are prevented from being invalid by imitating the mechanism of avoiding predators. Thus, the energy consumption of the network is reduced. Comparative analysis shows that the algorithm is simple and effective in wireless sensor network deployment. Compared with the optimized artificial fish swarm algorithm, the proposed algorithm exhibits advantages in network coverage, energy conservation, and obstacle avoidance.

  9. A man-made object detection for underwater TV

    Science.gov (United States)

    Cheng, Binbin; Wang, Wenwu; Chen, Yao

    2018-03-01

    It is a great challenging task to complete an automatic search of objects underwater. Usually the forward looking sonar is used to find the target, and then the initial identification of the target is completed by the side-scan sonar, and finally the confirmation of the target is accomplished by underwater TV. This paper presents an efficient method for automatic extraction of man-made sensitive targets in underwater TV. Firstly, the image of underwater TV is simplified with taking full advantage of the prior knowledge of the target and the background; then template matching technology is used for target detection; finally the target is confirmed by extracting parallel lines on the target contour. The algorithm is formulated for real-time execution on limited-memory commercial-of-the-shelf platforms and is capable of detection objects in underwater TV.

  10. Carbon Absorber Retrofit Equipment (CARE)

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Eric [Neumann Systems Group, Incorporated, Colorado Springs, CO (United States)

    2015-12-23

    During Project DE-FE0007528, CARE (Carbon Absorber Retrofit Equipment), Neumann Systems Group (NSG) designed, installed and tested a 0.5MW NeuStream® carbon dioxide (CO2) capture system using the patented NeuStream® absorber equipment and concentrated (6 molal) piperazine (PZ) as the solvent at Colorado Springs Utilities’ (CSU’s) Martin Drake pulverized coal (PC) power plant. The 36 month project included design, build and test phases. The 0.5MW NeuStream® CO2 capture system was successfully tested on flue gas from both coal and natural gas combustion sources and was shown to meet project objectives. Ninety percent CO2 removal was achieved with greater than 95% CO2product purity. The absorbers tested support a 90% reduction in absorber volume compared to packed towers and with an absorber parasitic power of less than 1% when configured for operation with a 550MW coal plant. The preliminary techno-economic analysis (TEA) performed by the Energy and Environmental Research Center (EERC) predicted an over-the-fence cost of $25.73/tonne of CO2 captured from a sub-critical PC plant.

  11. Additive manufacturing of RF absorbers

    Science.gov (United States)

    Mills, Matthew S.

    The ability of additive manufacturing techniques to fabricate integrated electromagnetic absorbers tuned for specific radio frequency bands within structural composites allows for unique combinations of mechanical and electromagnetic properties. These composites and films can be used for RF shielding of sensitive electromagnetic components through in-plane and out-of-plane RF absorption. Structural composites are a common building block of many commercial platforms. These platforms may be placed in situations in which there is a need for embedded RF absorbing properties along with structural properties. Instead of adding radar absorbing treatments to the external surface of existing structures, which adds increased size, weight and cost; it could prove to be advantageous to integrate the microwave absorbing properties directly into the composite during the fabrication process. In this thesis, a method based on additive manufacturing techniques of composites structures with prescribed electromagnetic loss, within the frequency range 1 to 26GHz, is presented. This method utilizes screen printing and nScrypt micro dispensing to pattern a carbon based ink onto low loss substrates. The materials chosen for this study will be presented, and the fabrication technique that these materials went through to create RF absorbing structures will be described. The calibration methods used, the modeling of the RF structures, and the applications in which this technology can be utilized will also be presented.

  12. Underwater welding using remote controlled robots. Development of remote underwater welding technology with a high power YAG laser

    International Nuclear Information System (INIS)

    Miwa, Yasuhiro; Sato, Syuuichi; Kojima, Toshio; Owaki, Katsura; Hirose, Naoya

    2002-01-01

    As components in nuclear power plant have been periodically carried out their inspection and repair to keep their integrity, on radioactive liquid wastes storage facility, because of difficulty on their inspection by human beings, some are remained without inspection, and even when capable of inspection, conversion from human works to remote operations is desired from a viewpoint of their operation efficiency upgrading. For response to these needs, some developments on a technology capable of carrying out inspection of their inside at underwater environment and repairing welding with YAG laser by means of remote operation, have been performed. Remote underwater inspection and repair technology is a combination technology of already applied underwater mobile technique (underwater inspection robot) with underwater YAG laser welding technique which is recently at actual using level. Therefore, this technology is composed of an inspection robot and a repair welding robot. And, testing results using the underwater inspection robot and welding test results using the underwater repair welding robot, were enough preferable to obtain forecasting applicable to actual apparatuses. This technology is especially effective for inspection and repair of inside of nuclear fuel cycle apparatuses and relatively high dose apparatuses, and can be thought to be applicable also to large capacity tanks, tanks dealing with harmful matters, underwater structures, and so on, in general industries. (G.K.)

  13. Water waves generated by underwater explosion

    CERN Document Server

    Mehaute, Bernard Le

    1996-01-01

    This is the first book on explosion-generated water waves. It presents the theoretical foundations and experimental results of the generation and propagation of impulsively generated waves resulting from underwater explosions. Many of the theories and concepts presented herein are applicable to other types of water waves, in particular, tsunamis and waves generated by the fall of a meteorite. Linear and nonlinear theories, as well as experimental calibrations, are presented for cases of deep and shallow water explosions. Propagation of transient waves on dissipative, nonuniform bathymetries to

  14. Radon dynamics in underwater thermal radon therapy

    International Nuclear Information System (INIS)

    Lettner, H.; Hofmann, W.; Winkler, R.; Rolle, R.; Foisner, W.

    1998-01-01

    At a facility for underwater thermal radon therapy in Bad Hofgastein, experiments were carried out with the aim of establishing radon in the air exhaled by the treated patients and of radon decay products on the skin of the patients. The time course of radon concentration in the exhaled air shows a maximum a few minutes after entering the bath, then the Rn concentration remains constant over the remaining time spent in the bath. Taking into account several simplifying assumptions, the average dose to the epidermis from radon daughters is about 50 μGy. (A.K.)

  15. Navigation System Fault Diagnosis for Underwater Vehicle

    DEFF Research Database (Denmark)

    Falkenberg, Thomas; Gregersen, Rene Tavs; Blanke, Mogens

    2014-01-01

    This paper demonstrates fault diagnosis on unmanned underwater vehicles (UUV) based on analysis of structure of the nonlinear dynamics. Residuals are generated using dierent approaches in structural analysis followed by statistical change detection. Hypothesis testing thresholds are made signal...... based to cope with non-ideal properties seen in real data. Detection of both sensor and thruster failures are demonstrated. Isolation is performed using the residual signature of detected faults and the change detection algorithm is used to assess severity of faults by estimating their magnitude...

  16. Adaptive Target Tracking for Underwater Maneuvering Targets.

    Science.gov (United States)

    1979-12-01

    concenetrate on the bearings-only approach. In this method the Observer monitors his bearing to the Source, over a period of time. Usually the Observer must...developed in [ 5] was earlier applied with much success to tracking maneuvering air targets. This approach will now be applied in the underwater environment...April 1977. [11] A. H. Jazwinski, Stochastic Processes and Filtering Theory, Academic Press, New York, 1970. [12] D. H. Halliday, and R. Resnick, Physics, John Wiley & Sons, Inc., New York, 1966. hI

  17. A sound absorptive element comprising an acoustic resonance nanofibrous membrane.

    Science.gov (United States)

    Kalinova, Klara

    2015-01-01

    As absorption of sound of lower frequencies is quite problematic with fibrous material made up of coarser fibers, development of highly efficient sound absorption material is called for. This is why this work deals with the development of new high sound absorption material. To absorb the low frequencies, especially the structures based on resonance principle of nanofibrous layers are used, when through resonance of some elements the acoustic energy is transferred into thermal energy. The goal of the invention is achieved by a sound absorbing means which contains resonance membrane formed by a layer of polymeric nanofibers, which is attached to a frame. For production of nanofibrous membranes, the cord electrospinning was used. The resonance membrane was then, upon impact of sound waves of low frequency, brought into forced vibrations, whereby the kinetic energy of the membrane was converted into thermal energy by friction of individual nanofibers, by the friction of the membrane with ambient air and possibly with other layers of material arranged in its proximity, and some of the energy was also transmitted to the frame, through which the vibrations of the resonance membrane were damped. The density and shape of the mesh of frame formations determine the resonance frequency of the acoustic means. The goal of the invention is therefore to eliminate or at least reduce the disadvantages of the present state of the art and to propose sound absorbing means that would be capable of absorbing, with good results sounds in as broadest frequency range as possible. Here, we also discussed some patents relevant to the topic.

  18. Water fugacity in absorbing polymers.

    Science.gov (United States)

    Burg, K J; Shalaby, S W

    1997-01-01

    Absorbable biomaterials, as dynamic systems, require special handling, processing, and characterization techniques beyond those of the traditional nonabsorbable materials. As the material degrades or absorbs, in vitro or in vivo, it undergoes structural, physical, and chemical changes. These changes in the base material may significantly impact the performance of a particular biomedical device; hence, it is important that the investigator consider the full range of properties that constitute the lifetime of a given absorbable material. The long term degradation study presented here sought to identify one such property, the change in water retention of a degrading oriented polylactide film. The investigation found through differential scanning calorimetry that later stages of degradation are often characterized by a stronger retention of water, potentially due to a higher number of polar carboxyl groups within the relatively hydrophobic polymer matrix.

  19. 46 CFR 115.650 - Alternative Hull Examination (AHE) Program options: Divers or underwater ROV.

    Science.gov (United States)

    2010-10-01

    ...: Divers or underwater ROV. 115.650 Section 115.650 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY... Alternative Hull Examination (AHE) Program options: Divers or underwater ROV. To complete your underwater survey, you may use divers or an underwater remotely operated vehicle (ROV). (a) If you use divers to...

  20. Adaptive inertial shock-absorber

    International Nuclear Information System (INIS)

    Faraj, Rami; Holnicki-Szulc, Jan; Knap, Lech; Seńko, Jarosław

    2016-01-01

    This paper introduces and discusses a new concept of impact absorption by means of impact energy management and storage in dedicated rotating inertial discs. The effectiveness of the concept is demonstrated in a selected case-study involving spinning management, a recently developed novel impact-absorber. A specific control technique performed on this device is demonstrated to be the main source of significant improvement in the overall efficiency of impact damping process. The influence of various parameters on the performance of the shock-absorber is investigated. Design and manufacturing challenges and directions of further research are formulated. (paper)

  1. Sound absorption of textile material using a microfibres resistive layer

    Science.gov (United States)

    Segura Alcaraz, M. P.; Bonet-Aracil, M.; Segura Alcaraz, J. G.; Montava Seguí, I.

    2017-10-01

    Acoustic comfort is a basic human need. One of the adverse effects of noise is its interference with speech discrimination. Textile materials are suitable to be used as sound absorptive materials and thus help to improve acoustic comfort in rooms. Micro-fibre fabrics can be considered as better sound absorbers than regular fibre fabrics mainly due to the higher surface of its fibres and bigger contact area with the air thus, allowing greater dissipation of sound energy. In this work, the use of a microfibre woven fabric as an upstream layer is analysed considering acoustic issues. Authors demonstrate it improves the sound absorption of a polyester nonwoven, resulting in a material suitable for absorption at the sound frequencies of the human voice.

  2. Analogy electromagnetism-acoustics: Validation and application to local impedance active control for sound absorption

    OpenAIRE

    Nicolas, Laurent; Furstoss, M.; Galland, Marie-Annick

    2007-01-01

    An analogy between electromagnetism and acoustics is presented in 2D. The propagation of sound in presence of absorbing material is modeled using an open boundary microwave package. Validation is performed through analytical and experimental results. Application to local impedance active control for free field sound absorption is finally described.

  3. 78 FR 13869 - Puget Sound Energy, Inc.; Puget Sound Energy, Inc.; Puget Sound Energy, Inc.; Puget Sound Energy...

    Science.gov (United States)

    2013-03-01

    ...-123-LNG; 12-128-NG; 12-148-NG; 12- 158-NG] Puget Sound Energy, Inc.; Puget Sound Energy, Inc.; Puget Sound Energy, Inc.; Puget Sound Energy, Inc.; Puget Sound Energy, Inc.; CE FLNG, LLC; Consolidated...-NG Puget Sound Energy, Inc Order granting long- term authority to import/export natural gas from/to...

  4. Tone-burst technique measures high-intensity sound absorption

    Science.gov (United States)

    Powell, J. G.; Van Houten, J. J.

    1971-01-01

    Tone-burst technique, in which narrow-bandwidth, short-duration sonic pulse is propagated down a standing-wave tube, measures sound absorbing capacity of materials used in jet engine noise abatement. Technique eliminates effects of tube losses and yields normal-incidence absorption coefficient of specimen.

  5. Underwater pipeline impact localization using piezoceramic transducers

    Science.gov (United States)

    Zhu, Junxiao; Ho, Siu Chun Michael; Patil, Devendra; Wang, Ning; Hirsch, Rachel; Song, Gangbing

    2017-10-01

    Reports indicated that impact events accounted for 47% of offshore pipeline failures, which calls for impact detection and localization for subsea pipelines. In this paper, an innovative method for rapid localization of impacts on underwater pipelines utilizing a novel determination technique for both arrival-time and group velocity (ATGV) of ultrasonic guided waves with lead zirconate titanate (PZT) transducers is described. PZT transducers mounted on the outer surface of a model pipeline were utilized to measure ultrasonic guided waves generated by impact events. Based on the signals from PZT sensors, the ATGV technique integrates wavelet decomposition, Hilbert transform and statistical analysis to pinpoint the arrival-time of the designated ultrasonic guided waves with a specific group velocity. Experimental results have verified the effectiveness and the localization accuracy for eight impact points along a model underwater pipeline. All estimations errors were small and were comparable with the wavelength of the designated ultrasonic guided waves. Furthermore, the method is robust against the low frequency structural vibration introduced by other external forces.

  6. GAS FLOW IN UNDERWATER BREATHING INSTALLATIONS

    Directory of Open Access Journals (Sweden)

    Anca CONSTANTIN

    2017-11-01

    Full Text Available The open circuit underwater breathing apparatus can be a one or two-stage regulator used in scuba diving or a two-stage regulator used in surface supplied installations. These installations are proper in underwater sites at small depth. The pneumatic circuit of a two-stage regulator is composed mainly of a first stage regulator mounted on the air cylinders and a second stage carried by the diver in his mouth. The two regulators are linked together by a medium pressure hose. The circuit opens when the depression created by the diver’s inhalation, in the second stage body, reaches a certain value. The second stage opening causes a transient movement, namely an expansion wave that propagates through the medium pressure hose to the first stage regulator. The first stage regulator opens and the air in the cylinders is allowed to flow to the diver. The longer the hose, the greater the duration of the expansion wave propagation. Investigations on the wave propagation offer data on the inspiration unsteady motion duration which influences the respiratory effort of the diver.

  7. An explanatory model of underwater adaptation

    Directory of Open Access Journals (Sweden)

    Joaquín Colodro

    Full Text Available The underwater environment is an extreme environment that requires a process of human adaptation with specific psychophysiological demands to ensure survival and productive activity. From the standpoint of existing models of intelligence, personality and performance, in this explanatory study we have analyzed the contribution of individual differences in explaining the adaptation of military personnel in a stressful environment. Structural equation analysis was employed to verify a model representing the direct effects of psychological variables on individual adaptation to an adverse environment, and we have been able to confirm, during basic military diving courses, the structural relationships among these variables and their ability to predict a third of the variance of a criterion that has been studied very little to date. In this way, we have confirmed in a sample of professionals (N = 575 the direct relationship of emotional adjustment, conscientiousness and general mental ability with underwater adaptation, as well as the inverse relationship of emotional reactivity. These constructs are the psychological basis for working under water, contributing to an improved adaptation to this environment and promoting risk prevention and safety in diving activities.

  8. Modelling cavitating flow around underwater missiles

    Directory of Open Access Journals (Sweden)

    Fabien Petitpas

    2011-12-01

    Full Text Available The diffuse interface model of Saurel et al. (2008 is used for the computation of compressible cavitating flows around underwater missiles. Such systems use gas injection and natural cavitation to reduce drag effects. Consequently material interfaces appear separating liquid and gas. These interfaces may have a really complex dynamics such that only a few formulations are able to predict their evolution. Contrarily to front tracking or interface reconstruction method the interfaces are computed as diffused numerical zones, that are captured in a routinely manner, as is done usually with gas dynamics solvers for shocks and contact discontinuity. With the present approach, a single set of partial differential equations is solved everywhere, with a single numerical scheme. This leads to very efficient solvers. The algorithm derived in Saurel et al. (2009 is used to compute cavitation pockets around solid bodies. It is first validated against experiments done in cavitation tunnel at CNU. Then it is used to compute flows around high speed underwater systems (Shkval-like missile. Performance data are then computed showing method ability to predict forces acting on the system.

  9. Hybrid Underwater Vehicle: ARV Design and Development

    Directory of Open Access Journals (Sweden)

    Zhigang DENG

    2014-02-01

    Full Text Available The development of SMU-I, a new autonomous & remotely-operated vehicle (ARV is described. Since it has both the characteristics of autonomous underwater vehicle (AUV and remote operated underwater vehicle (ROV, it is able to achieve precision fix station operation and manual timely intervention. In the paper the initial design of basic components, such as vehicle, propulsion, batteries etc. and the control design of motion are introduced and analyzed. ROV’s conventional cable is replaced by a fiber optic cable, which makes it available for high-bandwidth real-time video, data telemetry and high-quality teleoperation. Furthermore, with the aid of the manual real-time remote operation and ranging sonar, it also resolves the AUV’s conflicting issue, which can absolutely adapt the actual complex sea environment and satisfy the unknown mission need. The whole battery system is designed as two-battery banks, whose voltages and temperatures are monitored through CAN (controller area network bus to avoid battery fire and explosion. A fuzzy-PID controller is designed for its motion control, including depth control and direction control. The controller synthesizes the advantage of fuzzy control and PID control, utilizes the fuzzy rules to on-line tune the parameters of PID controller, and achieves a better control effect. Experiment results demonstrate to show the effectiveness of the test-bed.

  10. Software architecture of biomimetic underwater vehicle

    Science.gov (United States)

    Praczyk, Tomasz; Szymak, Piotr

    2016-05-01

    Autonomous underwater vehicles are vehicles that are entirely or partly independent of human decisions. In order to obtain operational independence, the vehicles have to be equipped with a specialized software. The main task of the software is to move the vehicle along a trajectory with collision avoidance. Moreover, the software has also to manage different devices installed on the vehicle board, e.g. to start and stop cameras, sonars etc. In addition to the software embedded on the vehicle board, the software responsible for managing the vehicle by the operator is also necessary. Its task is to define mission of the vehicle, to start, to stop the mission, to send emergency commands, to monitor vehicle parameters, and to control the vehicle in remotely operated mode. An important objective of the software is also to support development and tests of other software components. To this end, a simulation environment is necessary, i.e. simulation model of the vehicle and all its key devices, the model of the sea environment, and the software to visualize behavior of the vehicle. The paper presents architecture of the software designed for biomimetic autonomous underwater vehicle (BAUV) that is being constructed within the framework of the scientific project financed by Polish National Center of Research and Development.

  11. STABILITY OF UNDERWATER STRUCTURE UNDER WAVE ATTACK

    Directory of Open Access Journals (Sweden)

    C. Paotonan

    2012-02-01

    Full Text Available Geotube is, among others, a type of coastal structure that is increasingly accepted for coastal protection especially underwater breakwater. Besides its relatively low cost, it has other advantages such as flexibility, ease of construction and the fact that it can be filled with local sand material. Similar to all other coastal structures, it should also be stable under wave attack. A simple theoretical approach based on linear wave was adopted to estimate the stability of such structure. The theoretical solution was then compared with an experimental study. The experimental study was conducted at the Hydraulics and Hydrology Laboratory of Universitas Gadjah Mada. However, instead of a real geotube, PVC pipe was used where the weight of the PVC was varied by adjusting the volume of sand in the pipe. The result indicated that the agreement between the theoretical solution and the experiment was encouraging. The analytical solution may be utilized to predict underwater pipe stability under wave attack with certain degree of accuracy.

  12. Underwater noise levels in UK waters.

    Science.gov (United States)

    Merchant, Nathan D; Brookes, Kate L; Faulkner, Rebecca C; Bicknell, Anthony W J; Godley, Brendan J; Witt, Matthew J

    2016-11-10

    Underwater noise from human activities appears to be rising, with ramifications for acoustically sensitive marine organisms and the functioning of marine ecosystems. Policymakers are beginning to address the risk of ecological impact, but are constrained by a lack of data on current and historic noise levels. Here, we present the first nationally coordinated effort to quantify underwater noise levels, in support of UK policy objectives under the EU Marine Strategy Framework Directive (MSFD). Field measurements were made during 2013-2014 at twelve sites around the UK. Median noise levels ranged from 81.5-95.5 dB re 1 μPa for one-third octave bands from 63-500 Hz. Noise exposure varied considerably, with little anthropogenic influence at the Celtic Sea site, to several North Sea sites with persistent vessel noise. Comparison of acoustic metrics found that the RMS level (conventionally used to represent the mean) was highly skewed by outliers, exceeding the 97 th percentile at some frequencies. We conclude that environmental indicators of anthropogenic noise should instead use percentiles, to ensure statistical robustness. Power analysis indicated that at least three decades of continuous monitoring would be required to detect trends of similar magnitude to historic rises in noise levels observed in the Northeast Pacific.

  13. Computer simulations enhance experimental demonstrations in the underwater acoustics and sonar course

    Science.gov (United States)

    Korman, Murray S.

    2002-11-01

    Underwater acoustics and sonar (SP411) is a 3 hour course that is offered to midshipmen in their senior year. Typically, general science and oceanography majors, totaling 110 students/yr, enroll. Since this course is offered without a lab, the ''in class'' experience has been enhanced with the development (over many years) of our demo carts and computer workstations which surround the classroom. In a studio classroom atmosphere, students perform a variety of experiments in small groups. How can scientific visualizations best develop learning of complex interactions? Two examples are presented. PC-IMAT (personal curriculum interactive multisensor analysis training) simulations of multielement array steering support the theory and enhance the experiments that are performed in class such as the two-element array. Mathematica simulations involving the programming and animation of a point source in a rigid-rigid infinite parallel wave guide are used to stress the method of images, superposition, group and phase velocity and far-field modal pattern that is observed as a function of depth and source frequency. Later, students have fun using a ripple tank with an eye dropper to generate a point source between two adjustable parallel boundaries, and their understanding of ''underwater sound'' is greatly enhanced.

  14. Absorbing-and-diffusing coating

    OpenAIRE

    Tkalich, N. V.; Mokeev, Yu. G.; Onipko, A. F.; Vashchenko, V. F.; Topchev, M. D.; Glebov, V. V.; Ivanchenko, Dmitrij D.; Kolchigin, Nikolay N.; Yevdokimov, V. V.

    2003-01-01

    The paper presents the results of complex experimental research of the absorbing-and-diffusing material "Contrast". It is shown to be an efficient wideband-camouflage material in the radiolocation and the video bands. Ways for improving the material characteristics are outlined.

  15. Structure and Sound Absorption Properties of Spiral Vane Electrospun PVA/PEO Nanofiber Membranes

    OpenAIRE

    Huan Liu; Baoqi Zuo

    2018-01-01

    Noise pollution has become one of the four major pollution issues in the world and has drawn much attention recently. Controlling the sound source and using sound-absorbing materials reasonably is considered an effective way to reduce noise. Due to the high porosity and specific surface area, nanofibers membrane is widely used in the field of the sound absorption. Polyvinyl alcohol (PVA) and Polyethylene oxide (PEO) are both water-soluble polymers with good film-forming properties that can be...

  16. A Speed Control Method for Underwater Vehicle under Hydraulic Flexible Traction

    OpenAIRE

    Zhao, Yin; Xia, Ying-kai; Chen, Ying; Xu, Guo-Hua

    2015-01-01

    Underwater vehicle speed control methodology method is the focus of research in this study. Driven by a hydraulic flexible traction system, the underwater vehicle advances steadily on underwater guide rails, simulating an underwater environment for the carried device. Considering the influence of steel rope viscoelasticity and the control system traction structure feature, a mathematical model of the underwater vehicle driven by hydraulic flexible traction system is established. A speed contr...

  17. Coral larvae move toward reef sounds.

    Directory of Open Access Journals (Sweden)

    Mark J A Vermeij

    Full Text Available Free-swimming larvae of tropical corals go through a critical life-phase when they return from the open ocean to select a suitable settlement substrate. During the planktonic phase of their life cycle, the behaviours of small coral larvae (<1 mm that influence settlement success are difficult to observe in situ and are therefore largely unknown. Here, we show that coral larvae respond to acoustic cues that may facilitate detection of habitat from large distances and from upcurrent of preferred settlement locations. Using in situ choice chambers, we found that settling coral larvae were attracted to reef sounds, produced mainly by fish and crustaceans, which we broadcast underwater using loudspeakers. Our discovery that coral larvae can detect and respond to sound is the first description of an auditory response in the invertebrate phylum Cnidaria, which includes jellyfish, anemones, and hydroids as well as corals. If, like settlement-stage reef fish and crustaceans, coral larvae use reef noise as a cue for orientation, the alleviation of noise pollution in the marine environment may gain further urgency.

  18. Underwater television camera for monitoring inner side of pressure vessel

    International Nuclear Information System (INIS)

    Takayama, Kazuhiko.

    1997-01-01

    An underwater television support device equipped with a rotatable and vertically movable underwater television camera and an underwater television camera controlling device for monitoring images of the inside of the reactor core photographed by the underwater television camera to control the position of the underwater television camera and the underwater light are disposed on an upper lattice plate of a reactor pressure vessel. Both of them are electrically connected with each other by way of a cable to rapidly observe the inside of the reactor core by the underwater television camera. The reproducibility is extremely satisfactory by efficiently concentrating the position of the camera and image information upon inspection and observation. As a result, the steps for periodical inspection can be reduced to shorten the days for the periodical inspection. Since there is no requirement to withdraw fuel assemblies over a wide reactor core region, and the device can be used with the fuel assemblies being left as they are in the reactor, it is suitable for inspection of detectors for nuclear instrumentation. (N.H.)

  19. Underwater fiber-wireless communication with a passive front end

    Science.gov (United States)

    Xu, Jing; Sun, Bin; Lyu, Weichao; Kong, Meiwei; Sarwar, Rohail; Han, Jun; Zhang, Wei; Deng, Ning

    2017-11-01

    We propose and experimentally demonstrate a novel concept on underwater fiber-wireless (Fi-Wi) communication system with a fully passive wireless front end. A low-cost step-index (SI) plastic optical fiber (POF) together with a passive collimating lens at the front end composes the underwater Fi-Wi architecture. We have achieved a 1.71-Gb/s transmission at a mean BER of 4.97 × 10-3 (1.30 × 10-3 when using power loading) over a 50-m SI-POF and 2-m underwater wireless channel using orthogonal frequency division multiplexing (OFDM). Although the wireless part is very short, it actually plays a crucial role in practical underwater implementation, especially in deep sea. Compared with the wired solution (e.g. using a 52-m POF cable without the UWOC part), the proposed underwater Fi-Wi scheme can save optical wet-mate connectors that are sophisticated, very expensive and difficult to install in deep ocean. By combining high-capacity robust POF with the mobility and ubiquity of underwater wireless optical communication (UWOC), the proposed underwater Fi-Wi technology will find wide application in ocean exploration.

  20. Towards a Hybrid Approach to Context Reasoning for Underwater Robots

    Directory of Open Access Journals (Sweden)

    Xin Li

    2017-02-01

    Full Text Available Ontologies have been widely used to facilitate semantic interoperability and serve as a common information model in many applications or domains. The Smart and Networking Underwater Robots in Cooperation Meshes (SWARMs project, aiming to facilitate coordination and cooperation between heterogeneous underwater vehicles, also adopts ontologies to formalize information that is necessarily exchanged between vehicles. However, how to derive more useful contexts based on ontologies still remains a challenge. In particular, the extreme nature of the underwater environment introduces uncertainties in context data, thus imposing more difficulties in context reasoning. None of the existing context reasoning methods could individually deal with all intricacies in the underwater robot field. To this end, this paper presents the first proposal applying a hybrid context reasoning mechanism that includes ontological, rule-based, and Multi-Entity Bayesian Network (MEBN reasoning methods to reason about contexts and their uncertainties in the underwater robot field. The theoretical foundation of applying this reasoning mechanism in underwater robots is given by a case study on the oil spill monitoring. The simulated reasoning results are useful for further decision-making by operators or robots and they show that the consolidation of different reasoning methods is a promising approach for context reasoning in underwater robots.

  1. Underwater photography - A visual survey method

    Digital Repository Service at National Institute of Oceanography (India)

    Sharma, R.

    . Calculation of the area photographed on the seafloor (X= altitude of the camera, L= length of the photograph, B= breadth of the photograph, LxB=Area of the photograph) Fig. 3. Calculation of scale factor data and sounding data, need...: Hersey, J.B. (Ed.) Deep sea photography. The Johns Hopkins Press: Baltimore, 43-45 Photo data Navigation data Sounding data Processing seafloor/ sub-bottom features Correction / projection Interpolation Of position Estimation of water depth...

  2. The Textile Form of Sound

    DEFF Research Database (Denmark)

    Bendixen, Cecilie

    of sound. This issue is a part of a Ph.D. study at The Danish Design School in Copenhagen. Sound diffusion in architecture is a complex phenomenon. From the sound source the sound spreads in all directions as a sphere of wave fronts. When the sound is reflected from room boundaries or furniture, complex......Sound is a part of architecture, and sound is complex. Upon this, sound is invisible. How is it then possible to design visual objects that interact with the sound? This paper addresses the problem of how to get access to the complexity of sound and how to make textile material revealing the form...

  3. Behavioral responses of a harbor porpoise (Phocoena phocoena) to playbacks of broadband pile driving sounds.

    Science.gov (United States)

    Kastelein, Ronald A; van Heerden, Dorianne; Gransier, Robin; Hoek, Lean

    2013-12-01

    The high under-water sound pressure levels (SPLs) produced during pile driving to build offshore wind turbines may affect harbor porpoises. To estimate the discomfort threshold of pile driving sounds, a porpoise in a quiet pool was exposed to playbacks (46 strikes/min) at five SPLs (6 dB steps: 130-154 dB re 1 μPa). The spectrum of the impulsive sound resembled the spectrum of pile driving sound at tens of kilometers from the pile driving location in shallow water such as that found in the North Sea. The animal's behavior during test and baseline periods was compared. At and above a received broadband SPL of 136 dB re 1 μPa [zero-peak sound pressure level: 151 dB re 1 μPa; t90: 126 ms; sound exposure level of a single strike (SELss): 127 dB re 1 μPa(2) s] the porpoise's respiration rate increased in response to the pile driving sounds. At higher levels, he also jumped out of the water more often. Wild porpoises are expected to move tens of kilometers away from offshore pile driving locations; response distances will vary with context, the sounds' source level, parameters influencing sound propagation, and background noise levels. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Acoustical performance of porous absorber made from recycled rubber and polyurethane resin

    Directory of Open Access Journals (Sweden)

    Rubén Maderuelo-Sanz

    Full Text Available This paper reports an investigation of a new kind of material and its acoustical performance. The main component of this porous absorber is the ground tyre rubber (GTR with different particle sizes, from the shredding of tyres of heavy vehicles, mixed with different proportion of polyurethane resin. Acoustical properties were assessed according to ISO 10534 - 2: 1998. The data obtained show porous absorbers having a high sound absorption performance with low thicknesses and compared to some of the current models for the prediction of their absorptive properties. The use of this model constitutes a good tool in order to design a new sound absorber to solve two environmental problems, noise and environmental pollution.

  5. A Secure Communication Suite for Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Angelica Lo Duca

    2012-11-01

    Full Text Available In this paper we describe a security suite for Underwater Acoustic Sensor Networks comprising both fixed and mobile nodes. The security suite is composed of a secure routing protocol and a set of cryptographic primitives aimed at protecting the confidentiality and the integrity of underwater communication while taking into account the unique characteristics and constraints of the acoustic channel. By means of experiments and simulations based on real data, we show that the suite is suitable for an underwater networking environment as it introduces limited, and sometimes negligible, communication and power consumption overhead.

  6. Application of YAG laser processing in underwater welding and cutting

    International Nuclear Information System (INIS)

    Ohwaki, Katsura; Morita, Ichiro; Kojima, Toshio; Sato, Shuichi

    2002-01-01

    The high-power YAG laser is a new fabrication tool. The laser torch is easy to combine with complex with complex mechanics because of beam delivery through optical fiber. A direct underwater laser welding technology has been developed and applied to the preservation, maintenance and removal of nuclear power plants. For subdividing or removing operations for retirement of plants, the laser cutting properties were confirmed to allow a maximum cutting thickness of 80 mm. For repairing inner surface of stainless steel tanks, an underwater laser welding system using a remote-controlled robot was developed and the high quality of underwater laser welding was confirmed. (author)

  7. Centralised versus Decentralised Control Reconfiguration for Collaborating Underwater Robots

    DEFF Research Database (Denmark)

    Furno, Lidia; Nielsen, Mikkel Cornelius; Blanke, Mogens

    2015-01-01

    The present paper introduces an approach to fault-tolerant reconfiguration for collaborating underwater robots. Fault-tolerant reconfiguration is obtained using the virtual actuator approach, Steen (2005). The paper investigates properties of a centralised versus a decentralised implementation...... an underwater drill needs to be transported and positioned by three collaborating robots as part of an underwater autonomous operation....... and assesses the capabilities under communication constraints between the individual robots. In the centralised case, each robot sends information related to its own status to a unique virtual actuator that computes the necessary reconfiguration. In the decentralised case, each robot is equipped with its own...

  8. Adaptive Decentralized Control of Mobile Underwater Sensor Networks and Robots for Modeling Underwater Phenomena

    Directory of Open Access Journals (Sweden)

    Carrick Detweiler

    2014-05-01

    Full Text Available Understanding the dynamics of bodies of water and their impact on the global environment requires sensing information over the full volume of water. In this article, we develop a gradient-based decentralized controller that dynamically adjusts the depth of a network of underwater sensors to optimize sensing for computing maximally detailed volumetric models. We prove that the controller converges to a local minimum and show how the controller can be extended to work with hybrid robot and sensor network systems. We implement the controller on an underwater sensor network with depth adjustment capabilities. Through simulations and in-situ experiments, we verify the functionality and performance of the system and algorithm.

  9. Vocalisation Repertoire of Female Bluefin Gurnard (Chelidonichthys kumu in Captivity: Sound Structure, Context and Vocal Activity.

    Directory of Open Access Journals (Sweden)

    Craig A Radford

    Full Text Available Fish vocalisation is often a major component of underwater soundscapes. Therefore, interpretation of these soundscapes requires an understanding of the vocalisation characteristics of common soniferous fish species. This study of captive female bluefin gurnard, Chelidonichthys kumu, aims to formally characterise their vocalisation sounds and daily pattern of sound production. Four types of sound were produced and characterised, twice as many as previously reported in this species. These sounds fit two aural categories; grunt and growl, the mean peak frequencies for which ranged between 129 to 215 Hz. This species vocalized throughout the 24 hour period at an average rate of (18.5 ± 2.0 sounds fish-1 h-1 with an increase in vocalization rate at dawn and dusk. Competitive feeding did not elevate vocalisation as has been found in other gurnard species. Bluefin gurnard are common in coastal waters of New Zealand, Australia and Japan and, given their vocalization rate, are likely to be significant contributors to ambient underwater soundscape in these areas.

  10. Radiation sterilization of absorbent cotton and of absorbent gauze

    International Nuclear Information System (INIS)

    Hosobuchi, Kazunari; Oka, Mitsuru; Kaneko, Akira; Ishiwata, Hiroshi.

    1986-01-01

    The bioburden of absorbent cotton and of absorbent gauze and their physical and chemical characteristics after irradiation are investigated. The survey conducted on contaminants of 1890 cotton samples from 53 lots and 805 gauze samples from 56 lots showed maximum numbers of microbes per g of the cotton and gauze were 859 (an average of 21.4) and 777 (an average of 42.2), respectively. Isolation and microbiological and biochemical tests of representative microbes indicated that all of them, except one, were bacilli. The sterilization dose at 10 -6 of sterlity assurance level was found to be 2.0 Mrad when irradiated the spores loaded on paper strips and examined populations having graded D values from 0.10 to 0.28 Mrad. The sterilization dose would be about 1.5 Mrad if subjected the average numbers of contaminants observed in this study to irradiation. No significant differences were found between the irradiated samples and control up to 2 Mrad in tensile strength, change of color, absorbency, sedimentation rate, soluble substances, and pH of solutions used for immersion and other tests conventionally used. These results indicate that these products can be sterilized by irradiation. (author)

  11. Sound Insulation between Dwellings

    DEFF Research Database (Denmark)

    Rasmussen, Birgit

    2011-01-01

    Regulatory sound insulation requirements for dwellings exist in more than 30 countries in Europe. In some countries, requirements have existed since the 1950s. Findings from comparative studies show that sound insulation descriptors and requirements represent a high degree of diversity...... and initiate – where needed – improvement of sound insulation of new and existing dwellings in Europe to the benefit of the inhabitants and the society. A European COST Action TU0901 "Integrating and Harmonizing Sound Insulation Aspects in Sustainable Urban Housing Constructions", has been established and runs...... 2009-2013. The main objectives of TU0901 are to prepare proposals for harmonized sound insulation descriptors and for a European sound classification scheme with a number of quality classes for dwellings. Findings from the studies provide input for the discussions in COST TU0901. Data collected from 24...

  12. Task Allocation and Path Planning for Collaborative Autonomous Underwater Vehicles Operating through an Underwater Acoustic Network

    Directory of Open Access Journals (Sweden)

    Yueyue Deng

    2013-01-01

    Full Text Available Dynamic and unstructured multiple cooperative autonomous underwater vehicle (AUV missions are highly complex operations, and task allocation and path planning are made significantly more challenging under realistic underwater acoustic communication constraints. This paper presents a solution for the task allocation and path planning for multiple AUVs under marginal acoustic communication conditions: a location-aided task allocation framework (LAAF algorithm for multitarget task assignment and the grid-based multiobjective optimal programming (GMOOP mathematical model for finding an optimal vehicle command decision given a set of objectives and constraints. Both the LAAF and GMOOP algorithms are well suited in poor acoustic network condition and dynamic environment. Our research is based on an existing mobile ad hoc network underwater acoustic simulator and blind flooding routing protocol. Simulation results demonstrate that the location-aided auction strategy performs significantly better than the well-accepted auction algorithm developed by Bertsekas in terms of task-allocation time and network bandwidth consumption. We also demonstrate that the GMOOP path-planning technique provides an efficient method for executing multiobjective tasks by cooperative agents with limited communication capabilities. This is in contrast to existing multiobjective action selection methods that are limited to networks where constant, reliable communication is assumed to be available.

  13. Status of the ANTARES underwater neutrino telescope

    CERN Document Server

    Hallewell, G D

    2003-01-01

    The ANTARES Collaboration is constructing a deep underwater neutrino detector for operation at -2400 m off the French Mediterranean coast near Toulon. The detector, which will begin operation in 2004, will have an aperture of approx 0.1 km sup 2 , and will contain 900 photomultiplier tubes. The photomultiplier axes will be angled 45 deg. downward toward the seabed to observe the Cherenkov emissions of upward-going muons created by the interactions in or near the detector of high energy neutrinos traversing the Earth. These neutrinos arrive undeviated from a variety of galactic and extragalactic sources of astrophysical interest, and might be produced in the possible annihilation of dark matter neutralinos. The design and present status of the detector are summarized. Results from site evaluation and the development of supporting instrumentation are outlined.

  14. The NESTOR underwater neutrino telescope project

    Energy Technology Data Exchange (ETDEWEB)

    Rapidis, Petros A. [Institute of Nuclear Physics, National Center for Scientific Research ' Demokritos' , Athens 15310 (Greece)], E-mail: rapidis@inp.demokritos.gr

    2009-04-11

    The NESTOR collaboration is continuing its efforts towards deploying an underwater neutrino telescope. Further site studies (e.g. water light transmission measurements, sedimentation rates, etc.) are being carried out within the context of characterizing a site that may host the proposed KM3NeT infrastructure. In addition, following the successful deployment of a single floor of a NESTOR tower in 2003, five floors are now in the final stages of preparation. The use of these five floors in a form of a truncated tower together with four autonomous strings to be located some 300 m away from the tower is being contemplated. This arrangement, named NuBE (for Neutrino Burst Experiment), that may allow the detection neutrinos in coincidence with Gamma Ray Bursts, will be described.

  15. A Validation Process for Underwater Localization Algorithms

    Directory of Open Access Journals (Sweden)

    Marc Hildebrandt

    2014-09-01

    Full Text Available This paper describes the validation process of a localization algorithm for underwater vehicles. In order to develop new localization algorithms, it is essential to characterize them with regard to their accuracy, long-term stability and robustness to external sources of noise. This is only possible if a gold-standard reference localization (GSRL is available against which any new localization algorithm (NLA can be tested. This process requires a vehicle which carries all the required sensor and processing systems for both the GSRL and the NLA. This paper will show the necessity of such a validation process, briefly sketch the test vehicle and its capabilities, describe the challenges in computing the localizations of both the GSRL and the NLA simultaneously for comparison, and conclude with experimental data of real-world trials.

  16. Improved Underwater Excitation-Emission Matrix Fluorometer

    Science.gov (United States)

    Moore, Casey; daCunha, John; Rhoades, Bruce; Twardowski, Michael

    2007-01-01

    A compact, high-resolution, two-dimensional excitation-emission matrix fluorometer (EEMF) has been designed and built specifically for use in identifying and measuring the concentrations of organic compounds, including polluting hydrocarbons, in natural underwater settings. Heretofore, most EEMFs have been designed and built for installation in laboratories, where they are used to analyze the contents of samples collected in the field and brought to the laboratories. Because the present EEMF can be operated in the field, it is better suited to measurement of spatially and temporally varying concentrations of substances of interest. In excitation-emission matrix (EEM) fluorometry, fluorescence is excited by irradiating a sample at one or more wavelengths, and the fluorescent emission from the sample is measured at multiple wavelengths. When excitation is provided at only one wavelength, the technique is termed one-dimensional (1D) EEM fluorometry because the resulting matrix of fluorescence emission data (the EEM) contains only one row or column. When excitation is provided at multiple wavelengths, the technique is termed two-dimensional (2D) EEM fluorometry because the resulting EEM contains multiple rows and columns. EEM fluorometry - especially the 2D variety - is well established as a means of simultaneously detecting numerous dissolved and particulate compounds in water. Each compound or pool of compounds has a unique spectral fluorescence signature, and each EEM is rich in information content, in that it can contain multiple fluorescence signatures. By use of deconvolution and/or other mixture-analyses techniques, it is often possible to isolate the spectral signature of compounds of interest, even when their fluorescence spectra overlap. What distinguishes the present 2D EEMF over prior laboratory-type 2D EEMFs are several improvements in packaging (including a sealed housing) and other aspects of design that render it suitable for use in natural underwater

  17. Adaptive control of nonlinear underwater robotic systems

    Directory of Open Access Journals (Sweden)

    Thor I. Fossen

    1991-04-01

    Full Text Available The problem of controlling underwater mobile robots in 6 degrees of freedom (DOF is addressed. Uncertainties in the input matrix due to partly known nonlinear thruster characteristics are modeled as multiplicative input uncertainty. This paper proposes two methods to compensate for the model uncertainties: (1 an adaptive passivity-based control scheme and (2 deriving a hybrid (adaptive and sliding controller. The hybrid controller consists of a switching term which compensates for uncertainties in the input matrix and an on-line parameter estimation algorithm. Global stability is ensured by applying Barbalat's Lyapunovlike lemma. The hybrid controller is simulated for the horizontal motion of the Norwegian Experimental Remotely Operated Vehicle (NEROV.

  18. Collision Detection for Underwater ROV Manipulator Systems.

    Science.gov (United States)

    Sivčev, Satja; Rossi, Matija; Coleman, Joseph; Omerdić, Edin; Dooly, Gerard; Toal, Daniel

    2018-04-06

    Work-class ROVs equipped with robotic manipulators are extensively used for subsea intervention operations. Manipulators are teleoperated by human pilots relying on visual feedback from the worksite. Operating in a remote environment, with limited pilot perception and poor visibility, manipulator collisions which may cause significant damage are likely to happen. This paper presents a real-time collision detection algorithm for marine robotic manipulation. The proposed collision detection mechanism is developed, integrated into a commercial ROV manipulator control system, and successfully evaluated in simulations and experimental setup using a real industry standard underwater manipulator. The presented collision sensing solution has a potential to be a useful pilot assisting tool that can reduce the task load, operational time, and costs of subsea inspection, repair, and maintenance operations.

  19. The NESTOR underwater neutrino telescope project

    International Nuclear Information System (INIS)

    Rapidis, Petros A.

    2009-01-01

    The NESTOR collaboration is continuing its efforts towards deploying an underwater neutrino telescope. Further site studies (e.g. water light transmission measurements, sedimentation rates, etc.) are being carried out within the context of characterizing a site that may host the proposed KM3NeT infrastructure. In addition, following the successful deployment of a single floor of a NESTOR tower in 2003, five floors are now in the final stages of preparation. The use of these five floors in a form of a truncated tower together with four autonomous strings to be located some 300 m away from the tower is being contemplated. This arrangement, named NuBE (for Neutrino Burst Experiment), that may allow the detection neutrinos in coincidence with Gamma Ray Bursts, will be described.

  20. Ontogenetic investigation of underwater hearing capabilities in loggerhead sea turtles (Caretta caretta) using a dual testing approach.

    Science.gov (United States)

    Lavender, Ashley L; Bartol, Soraya M; Bartol, Ian K

    2014-07-15

    Sea turtles reside in different acoustic environments with each life history stage and may have different hearing capacity throughout ontogeny. For this study, two independent yet complementary techniques for hearing assessment, i.e. behavioral and electrophysiological audiometry, were employed to (1) measure hearing in post-hatchling and juvenile loggerhead sea turtles Caretta caretta (19-62 cm straight carapace length) to determine whether these migratory turtles exhibit an ontogenetic shift in underwater auditory detection and (2) evaluate whether hearing frequency range and threshold sensitivity are consistent in behavioral and electrophysiological tests. Behavioral trials first required training turtles to respond to known frequencies, a multi-stage, time-intensive process, and then recording their behavior when they were presented with sound stimuli from an underwater speaker using a two-response forced-choice paradigm. Electrophysiological experiments involved submerging restrained, fully conscious turtles just below the air-water interface and recording auditory evoked potentials (AEPs) when sound stimuli were presented using an underwater speaker. No significant differences in behavior-derived auditory thresholds or AEP-derived auditory thresholds were detected between post-hatchling and juvenile sea turtles. While hearing frequency range (50-1000/1100 Hz) and highest sensitivity (100-400 Hz) were consistent in audiograms pooled by size class for both behavior and AEP experiments, both post-hatchlings and juveniles had significantly higher AEP-derived than behavior-derived auditory thresholds, indicating that behavioral assessment is a more sensitive testing approach. The results from this study suggest that post-hatchling and juvenile loggerhead sea turtles are low-frequency specialists, exhibiting little differences in threshold sensitivity and frequency bandwidth despite residence in acoustically distinct environments throughout ontogeny. © 2014

  1. Morphing hull implementation for unmanned underwater vehicles

    International Nuclear Information System (INIS)

    Miller, Timothy F; Gandhi, Farhan; Rufino, Russell J

    2013-01-01

    There has been much interest and work in the area of morphing aircraft since the 1980s. Morphing could also potentially benefit unmanned underwater vehicles (UUVs). The current paper envisions a UUV with an interior pressure hull and a variable diameter outer flexible hull with fuel stored in the annulus between, and presents a mechanism to realize diameter change of the outer hull. The outer hull diameter of UUVs designed for very long endurance/range could be progressively reduced as fuel was consumed, thereby reducing drag and further increasing endurance and range capability. Diameter morphing could also be advantageous for compact storage of UUVs. A prototype is fabricated to represent an axial section of such a morphing diameter UUV. Diameter change is achieved using eight morphing trusses arranged equidistant around the circumference of the representative interior rigid hull. Each morphing truss has a lower rail (attached to the rigid hull) and an upper rail with V-linkages between, at either ends of the rail. Horizontal motion of the feet of the V-linkages (sliding in the lower rail) results in vertical motion of the upper rail which in turn produces diameter change of the outer hull. For the prototype built and tested, a 63% increase in outer diameter from 12.75″ to 20.75″ was achieved. The introduction of a stretched latex representative flexible skin around the outer rails increased actuation force requirement and led to a propensity for the wheel-in-track sliders in the morphing truss to bind. It is anticipated that this could be overcome with higher precision manufacturing. In addition to symmetric actuation of the morphing trusses resulting in diameter change, the paper also shows that with asymmetric actuation the hull cross-section shape can be changed (for example, from a circular section for underwater operation to a V-section for surface operations). (paper)

  2. On sampling the ocean using underwater gliders

    Science.gov (United States)

    Rudnick, Daniel L.; Cole, Sylvia T.

    2011-08-01

    The sampling characteristics of an underwater glider are addressed through comparison with contemporaneous measurements from a ship survey using a towed vehicle. The comparison uses the underwater glider Spray and the towed vehicle SeaSoar north of Hawaii along 158°W between 22.75°N and 34.5°N. A Spray dive from the surface to 1000 m and back took 5.6 h and covered 5.3 km, resulting in a horizontal speed of 0.26 m s-1. SeaSoar undulated between the surface and 400 m, completing a cycle in 11 min while covering 2.6 km, for a speed of 3.9 m s-1. Adjacent profiles of temperature and salinity are compared between the two platforms to prove that each is accurate. Spray and SeaSoar data are compared through sections, isopycnal spatial series, and wave number spectra. The relative slowness of the glider results in the projection of high-frequency oceanic variability, such as internal waves, onto spatial structure. The projection is caused by Doppler smearing because of finite speed and aliasing due to discrete sampling. The projected variability is apparent in properties measured on depth surfaces or in isopycnal depth. No projected variability is seen in observations of properties on constant density surfaces because internal waves are intrinsically filtered. Wave number spectra suggest that projected variability affects properties at constant depth at wavelengths shorter than 30 km. These results imply that isobaric quantities, like geostrophic shear, are valid at wavelengths longer than 30 km, while isopycnal quantities, like spice, may be analyzed for scales as small as a glider measures.

  3. Short Communication Evaluation of an underwater biopsy probe for ...

    African Journals Online (AJOL)

    lethal methods may become an increasingly useful tool to investigate shark populations where researchers encounter logistical or conservation-related constraints. Keywords: biopsy probe, laser photogrammetry, non-lethal sampling, underwater ...

  4. Digital sonar design in underwater acoustics principles and applications

    CERN Document Server

    Li, Qihu

    2012-01-01

    "Digital Sonar Design in Underwater Acoustics Principles and Applications" provides comprehensive and up-to-date coverage of research on sonar design, including the basic theory and techniques of digital signal processing, basic concept of information theory, ocean acoustics, underwater acoustic signal propagation theory, and underwater signal processing theory. This book discusses the general design procedure and approaches to implementation, the design method, system simulation theory and techniques, sonar tests in the laboratory, lake and sea, and practical validation criteria and methods for digital sonar design. It is intended for researchers in the fields of underwater signal processing and sonar design, and also for navy officers and ocean explorers. Qihu Li is a professor at the Institute of Acoustics, Chinese Academy of Sciences, and an academician of the Chinese Academy of Sciences.

  5. Automated Underwater Image Restoration and Retrieval of Related Optical Properties

    National Research Council Canada - National Science Library

    Hou, Weilin; Gray, Deric J; Weidemann, Alan D; Fournier, Georges R; Forand, J. L

    2007-01-01

    ...) in the spatial domain and the modulation transfer function (MTF) in the frequency domain. Due to the intensity variations involved in underwater sensing, denoising is carefully carried out by wavelet decompositions...

  6. Wireless Underwater Monitoring Systems Based on Energy Harvestings

    Directory of Open Access Journals (Sweden)

    Sea-Hee HWANGBO

    2013-01-01

    Full Text Available One of the important research fields for aquatic exploitation and conservation is underwater wireless sensor network. Since limited energy source for underwater nodes and devices is a main open problem, in this paper, we propose wireless underwater monitoring systems powered by energy harvester which resolves the energy constraint. The target system generates renewable energy from energy harvester and shares the energy with underwater sensor nodes. For the realization of the system, key components to be investigated are discriminated as follows: acoustic modem, actuator, smart battery charge controller, energy harvester and wireless power transfer module. By developing acoustic modem, actuator and smart battery charge controller and utilizing off-the-shelf energy harvester and wireless power transfer module, we design and implement a prototype of the system. Also, we verify the feasibility of concept of target system by conducting indoor and outdoor experiments.

  7. Trade-off Analysis of Underwater Acoustic Sensor Networks

    Science.gov (United States)

    Tuna, G.; Das, R.

    2017-09-01

    In the last couple of decades, Underwater Acoustic Sensor Networks (UASNs) were started to be used for various commercial and non-commercial purposes. However, in underwater environments, there are some specific inherent constraints, such as high bit error rate, variable and large propagation delay, limited bandwidth capacity, and short-range communications, which severely degrade the performance of UASNs and limit the lifetime of underwater sensor nodes as well. Therefore, proving reliability of UASN applications poses a challenge. In this study, we try to balance energy consumption of underwater acoustic sensor networks and minimize end-to-end delay using an efficient node placement strategy. Our simulation results reveal that if the number of hops is reduced, energy consumption can be reduced. However, this increases end-to-end delay. Hence, application-specific requirements must be taken into consideration when determining a strategy for node deployment.

  8. Object detection from images obtained through underwater turbulence medium

    Science.gov (United States)

    Furhad, Md. Hasan; Tahtali, Murat; Lambert, Andrew

    2017-09-01

    Imaging through underwater experiences severe distortions due to random fluctuations of temperature and salinity in water, which produces underwater turbulence through diffraction limited blur. Lights reflecting from objects perturb and attenuate contrast, making the recognition of objects of interest difficult. Thus, the information available for detecting underwater objects of interest becomes a challenging task as they have inherent confusion among the background, foreground and other image properties. In this paper, a saliency-based approach is proposed to detect the objects acquired through an underwater turbulent medium. This approach has drawn attention among a wide range of computer vision applications, such as image retrieval, artificial intelligence, neuro-imaging and object detection. The image is first processed through a deblurring filter. Next, a saliency technique is used on the image for object detection. In this step, a saliency map that highlights the target regions is generated and then a graph-based model is proposed to extract these target regions for object detection.

  9. Filming Underwater in 3d Respecting Stereographic Rules

    Science.gov (United States)

    Rinaldi, R.; Hordosch, H.

    2015-04-01

    After an experimental phase of many years, 3D filming is now effective and successful. Improvements are still possible, but the film industry achieved memorable success on 3D movie's box offices due to the overall quality of its products. Special environments such as space ("Gravity") and the underwater realm look perfect to be reproduced in 3D. "Filming in space" was possible in "Gravity" using special effects and computer graphic. The underwater realm is still difficult to be handled. Underwater filming in 3D was not that easy and effective as filming in 2D, since not long ago. After almost 3 years of research, a French, Austrian and Italian team realized a perfect tool to film underwater, in 3D, without any constrains. This allows filmmakers to bring the audience deep inside an environment where they most probably will never have the chance to be.

  10. Collision Avoidance of Moving Obstacles for Underwater Robots

    Directory of Open Access Journals (Sweden)

    KWON KYOUNG YOUB

    2006-10-01

    Full Text Available A fuzzy logic for autonomous navigation of underwater robot is proposed in this paper. The VFF(Virtual Force Field algorithm, which is widely used in the field of mobile robot, is modified for application to the autonomous navigation of underwater robot. This Modified Virtual Force Field(MVFF algorithm using the fuzzy logic can be used in either track keeping or obstacle avoidance. Fuzzy logics are devised to handle various situations which can be faced during autonomous navigation of underwater robot. A graphic simulator based on OpenGL for an autonomous navigation has been developed. The good performance of the proposed MVFF algorithm is verified through computer simulations on an underwater robot.

  11. Multi-layer protective armour for underwater shock wave mitigation

    Directory of Open Access Journals (Sweden)

    Ahmed Hawass

    2015-12-01

    The strain gauge data and displacement sensors results showed that the multi-layer plates have higher level of underwater shock wave mitigation than the triple aluminum plates with strain and deflection of nearly 50%.

  12. Underwater image enhancement through depth estimation based on random forest

    Science.gov (United States)

    Tai, Shen-Chuan; Tsai, Ting-Chou; Huang, Jyun-Han

    2017-11-01

    Light absorption and scattering in underwater environments can result in low-contrast images with a distinct color cast. This paper proposes a systematic framework for the enhancement of underwater images. Light transmission is estimated using the random forest algorithm. RGB values, luminance, color difference, blurriness, and the dark channel are treated as features in training and estimation. Transmission is calculated using an ensemble machine learning algorithm to deal with a variety of conditions encountered in underwater environments. A color compensation and contrast enhancement algorithm based on depth information was also developed with the aim of improving the visual quality of underwater images. Experimental results demonstrate that the proposed scheme outperforms existing methods with regard to subjective visual quality as well as objective measurements.

  13. Navigation of autonomous underwater vehicle using extended kalman filter

    Digital Repository Service at National Institute of Oceanography (India)

    Ranjan, T.N.; Nherakkol, A.; Navelkar, G.S.

    To navigate the Autonomous Underwater Vehicle (AUV) accurately is one of the most important aspects in its application. A truly autonomous vehicle must determine its position which requires the optimal integration of all available attitude...

  14. Euclidean reconstruction of natural underwater scenes using optic imagery sequence

    Science.gov (United States)

    Hu, Han

    The development of maritime applications require monitoring, studying and preserving of detailed and close observation on the underwater seafloor and objects. Stereo vision offers advanced technologies to build 3D models from 2D still overlapping optic images in a relatively inexpensive way. However, while image stereo matching is a necessary step in 3D reconstruction procedure, even the most robust dense matching techniques are not guaranteed to work for underwater images due to the challenging aquatic environment. In this thesis, in addition to a detailed introduction and research on the key components of building 3D models from optic images, a robust modified quasi-dense matching algorithm based on correspondence propagation and adaptive least square matching for underwater images is proposed and applied to some typical underwater image datasets. The experiments demonstrate the robustness and good performance of the proposed matching approach.

  15. Increasing the efficiency of thermoacoustic carbon nanotube sound projectors.

    Science.gov (United States)

    Aliev, Ali E; Gartstein, Yuri N; Baughman, Ray H

    2013-06-14

    Carbon nanotubes (CNTs) can generate smooth-spectra sound emission over a wide frequency range (1-10(5) Hz) by means of thermoacoustics (TA). However, in the low frequencies f, where the need for large area sound projectors is high, the sound generation efficiency η of open CNT sheets is low, since η [proportionality] f(2). Together with this problem, the nanoscale thickness of CNT sheets, their high sensitivity to the environment and the high surface temperatures useful for TA sound generation are other drawbacks, which we address here by protective encapsulation of free-standing CNT sheets in inert gases. We provide an extensive experimental study of such closed systems for different thermodynamic regimes and rationalize our observations within a basic theoretical framework. The observed sound pressure levels for encapsulated argon filled TA transducers (130 dB in air and 200 dB underwater in the near field at 5 cm distance, and 100 and 170 dB in the far field at 1 m distance) are Q times higher than those for open systems, where Q is the resonant quality factor of the thin enclosure plates. Moreover, the sound generation efficiency of the encapsulated system increases toward low frequencies (η [proportionality] 1/f(2)). Another method to increase η in the low frequency region is by modulation of the applied high frequency carrier current with a low frequency resonant envelope. This approach enables sound generation at the frequency of the applied current without the need for additional energy-consuming biasing. The acoustical and geometrical parameters providing further increases in efficiency and transduction performance for resonant systems are discussed.

  16. The Textile Form of Sound

    DEFF Research Database (Denmark)

    Bendixen, Cecilie

    three-dimensional geometries of interfering spheres are created. Textiles are generally a very good sound dampening material. To dampen the sound most effective it should be placed where the sound energy is highest. To find these invisible spots of energy and to reveal the geometry of them, two......Sound is a part of architecture, and sound is complex. Upon this, sound is invisible. How is it then possible to design visual objects that interact with the sound? This paper addresses the problem of how to get access to the complexity of sound and how to make textile material revealing the form...... of sound. This issue is a part of a Ph.D. study at The Danish Design School in Copenhagen. Sound diffusion in architecture is a complex phenomenon. From the sound source the sound spreads in all directions as a sphere of wave fronts. When the sound is reflected from room boundaries or furniture, complex...

  17. Underwater acoustic communications. From point-to-point to networks

    OpenAIRE

    Jesus, S. M.

    2013-01-01

    This is a review presentation that addresses recent developments in underwater acoustic telemetry as a tool for ocean observation, monitoring and protection. Distributed sensing is a paradigm with important reflections in oceanic technology where bottom installed structures can not always be connected to a central hub through cabled networks. Moreover, recent developments in ocean robotics lead to the off-the-shelf availability of autonomous underwater vehicles that rely on wireless communica...

  18. Estimation of underwater acoustic fields at high frequencies

    OpenAIRE

    Temsamani, A.B.; Vandenplas, S.; Van Biesen, L.

    2001-01-01

    In this work a parametric modeling of the underwater acoustic field is investigated in a laboratory scale at high frequencies (150-850 kHz). The aim is to develop experimentally verifiable theoretical models to investigate the acoustic field propagation in elastic and viscoelastic or porous media. To achieve this goal, the efforts have been directed to three integral parts pertaining to the development of the methods. The first part deals with the modeling of the underwater acoustic field fol...

  19. Strong tracking adaptive Kalman filters for underwater vehicle dead reckoning

    Science.gov (United States)

    Xiao, Kun; Fang, Shao-Ji; Pang, Yong-Jie

    2007-06-01

    To impove underwater vehicle dead reckoning, a developed strong tracking adaptive kalman filter is proposed. The filter is improved with an additional adaptive factor and an estimator of measurement noise covariance. Since the magnitude of fading factor is changed adaptively, the tracking ability of the filter is still enhanced in low velocity condition of underwater vehicles. The results of simulation tests prove the presented filter effective.

  20. Underwater striling engine design with modified one-dimensional model

    OpenAIRE

    Li, Daijin; Qin, Kan; Luo, Kai

    2015-01-01

    Stirling engines are regarded as an efficient and promising power system for underwater devices. Currently, many researches on one-dimensional model is used to evaluate thermodynamic performance of Stirling engine, but in which there are still some aspects which cannot be modeled with proper mathematical models such as mechanical loss or auxiliary power. In this paper, a four-cylinder double-acting Stirling engine for Unmanned Underwater Vehicles (UUVs) is discussed. And a one-dimensional mod...

  1. Characterization of ships as sources of underwater noise

    OpenAIRE

    Jong, C.A.F. de

    2009-01-01

    There is a growing interest in the possible impact of anthropogenic underwater noise on marine life [1]. One of the concerns is the increasing contribution of shipping noise, with the growing number and size of commercial ships. Traditionally, underwater radiated noise control was only of interest for naval [2,3] and fishery research vessels [4]. Due to the potential environmental impact, it becomes also relevant for commercial shipping. The challenge is to bring the expertise from the naval ...

  2. Remote Underwater Characterization System - Innovative Technology Summary Report

    International Nuclear Information System (INIS)

    Willis, Walter David

    1999-01-01

    Characterization and inspection of water-cooled and moderated nuclear reactors and fuel storage pools requires equipment capable of operating underwater. Similarly, the deactivation and decommissioning of older nuclear facilities often requires the facility owner to accurately characterize underwater structures and equipment which may have been sitting idle for years. The underwater characterization equipment is often required to operate at depths exceeding 20 ft (6.1 m) and in relatively confined or congested spaces. The typical baseline approach has been the use of radiation detectors and underwater cameras mounted on long poles, or stationary cameras with pan and tilt features mounted on the sides of the underwater facility. There is a perceived need for an inexpensive, more mobile method of performing close-up inspection and radiation measurements in confined spaces underwater. The Remote Underwater Characterization System (RUCS) is a small, remotely operated submersible vehicle intended to serve multiple purposes in underwater nuclear operations. It is based on the commercially-available ''Scallop'' vehicle, but has been modified by Department of Energy's Robotics Technology Development Program to add auto-depth control, and vehicle orientation and depth monitoring at the operator control panel. The RUCS is designed to provide visual and gamma radiation characterization, even in confined or limited access areas. It was demonstrated in August 1998 at Idaho National Engineering and environmental Laboratory (INEEL) as part of the INEEL Large Scale Demonstration and Deployment Project. During the demonstration it was compared in a ''head-to-head'' fashion with the baseline characterization technology. This paper summarizes the results of the demonstration and lessons learned; comparing and contrasting both technologies in the areas of cost, visual characterization, radiological characterization, and overall operations

  3. Terminal homing position estimation forAutonomous underwater vehicle docking

    Science.gov (United States)

    2017-06-01

    79  ix LIST OF FIGURES Figure 1.  NPS REMUS 100 with WHOI Docking Station. Source: [1...underwater missions were short and quick . Now, with advanced technology, underwater missions can be as long as the user desires. The new AUVs have...the full information problem. In order to use the MHE approach for real-time applications, the optimization process should be quick and accurate

  4. A potential flow based flight simulator for an underwater glider

    OpenAIRE

    Phoemsapthawee, Surasak; Le Boulluec, Marc; Laurens, Jean-marc; Deniset, Francois

    2013-01-01

    Underwater gliders are recent innovative types of autonomous underwater vehicles (AUVs) used in ocean exploration and observation. They adjust their buoyancy to dive and to return to the ocean surface. During the change of altitude, they use the hydrodynamic forces developed by their wings to move forward. Their flights are controlled by changing the position of their centers of gravity and their buoyancy to adjust their trim and heel angles. For better flight control, the understanding of th...

  5. Analytical and Numerical Optimal Motion Planning for an Underwater Glider

    OpenAIRE

    Kraus, Robert J.

    2010-01-01

    The use of autonomous underwater vehicles (AUVs) for oceanic observation and research is becoming more common. Underwater gliders are a specific class of AUV that do not use conventional propulsion. Instead they change their buoyancy and center of mass location to control attitude and trajectory. The vehicles spend most of their time in long, steady glides, so even minor improvements in glide range can be magnified over multiple dives. This dissertation presents a rigid-body dynamic system...

  6. Boundary curvature effects on gas bubble oscillations in underwater explosion

    OpenAIRE

    Matsumoto, Kazuhiro

    1996-01-01

    The oscillation of a gas bubble produced as a result of underwater explosion could cause the severe whipping damage on nearby marine vehicle. The effects of rigid boundary curvatures to explosive gas bubble oscillation behavior in underwater were investigated. The analyses were conducted using a multimaterial Lagrangian-Eulerian finite element code, MSC/DYTRAN. The incident shock wave pressure, bubble pulse pressure, gas bubble radius and period were calculated for the case of detonation of a...

  7. Deep Learning Methods for Underwater Target Feature Extraction and Recognition

    Directory of Open Access Journals (Sweden)

    Gang Hu

    2018-01-01

    Full Text Available The classification and recognition technology of underwater acoustic signal were always an important research content in the field of underwater acoustic signal processing. Currently, wavelet transform, Hilbert-Huang transform, and Mel frequency cepstral coefficients are used as a method of underwater acoustic signal feature extraction. In this paper, a method for feature extraction and identification of underwater noise data based on CNN and ELM is proposed. An automatic feature extraction method of underwater acoustic signals is proposed using depth convolution network. An underwater target recognition classifier is based on extreme learning machine. Although convolution neural networks can execute both feature extraction and classification, their function mainly relies on a full connection layer, which is trained by gradient descent-based; the generalization ability is limited and suboptimal, so an extreme learning machine (ELM was used in classification stage. Firstly, CNN learns deep and robust features, followed by the removing of the fully connected layers. Then ELM fed with the CNN features is used as the classifier to conduct an excellent classification. Experiments on the actual data set of civil ships obtained 93.04% recognition rate; compared to the traditional Mel frequency cepstral coefficients and Hilbert-Huang feature, recognition rate greatly improved.

  8. Optimal Node Placement in Underwater Acoustic Sensor Network

    KAUST Repository

    Felemban, Muhamad

    2011-10-01

    Almost 70% of planet Earth is covered by water. A large percentage of underwater environment is unexplored. In the past two decades, there has been an increase in the interest of exploring and monitoring underwater life among scientists and in industry. Underwater operations are extremely difficult due to the lack of cheap and efficient means. Recently, Wireless Sensor Networks have been introduced in underwater environment applications. However, underwater communication via acoustic waves is subject to several performance limitations, which makes the relevant research issues very different from those on land. In this thesis, we investigate node placement for building an initial Underwater Wireless Sensor Network infrastructure. Firstly, we formulated the problem into a nonlinear mathematic program with objectives of minimizing the total transmission loss under a given number of sensor nodes and targeted volume. We conducted experiments to verify the proposed formulation, which is solved using Matlab optimization tool. We represented each node with a truncated octahedron to fill out the 3D space. The truncated octahedrons are tiled in the 3D space with each node in the center where locations of the nodes are given using 3D coordinates. Results are supported using ns-3 simulator. Results from simulation are consistent with the obtained results from mathematical model with less than 10% error.

  9. Performance Evaluation of Hybrid Acoustic-Optical Underwater Swarm Networks

    Directory of Open Access Journals (Sweden)

    Samuela PERSIA

    2016-04-01

    Full Text Available The Underwater Swarm is a particular Underwater Network configuration characterized by nodes very close one to each other, with mobility capability. The structure of the network is that of a distributed network, in which the nodes, through the exchange of control information, will take decisions in collaborative manner. This type of network raises challenges for its effective design and development, for which the only use of acoustic communication as traditionally suggested in underwater communication could be not enough. A new emerging solution could be a hybrid solution that combines the use of acoustic and optical channel in order to overcome the acoustic channel limitations in underwater environment. In this work, we want to investigate how the acoustic and optical communications influence the Underwater Swarm performance by considering the Low Layers Protocols (Physical Layer, Data Link Layer and Network Layer effects over the two different propagation technologies. Performance simulations have been carried out to suggest how the new hybrid system could be designed. This study will permit to provide useful analysis for the real implementation of an Underwater Swarm based on hybrid communication technology.

  10. The sounds of nanotechnology

    Science.gov (United States)

    Campbell, Norah; Deane, Cormac; Murphy, Padraig

    2017-07-01

    Public perceptions of nanotechnology are shaped by sound in surprising ways. Our analysis of the audiovisual techniques employed by nanotechnology stakeholders shows that well-chosen sounds can help to win public trust, create value and convey the weird reality of objects on the nanoscale.

  11. Poetry Pages. Sound Effects.

    Science.gov (United States)

    Fina, Allan de

    1992-01-01

    Explains how elementary teachers can help students understand onomatopoeia, suggesting that they define onomatopoeia, share examples of it, read poems and have students discuss onomatopoeic words, act out common household sounds, write about sound effects, and create choral readings of onomatopoeic poems. Two appropriate poems are included. (SM)

  12. Sound propagation in cities

    NARCIS (Netherlands)

    Salomons, E.; Polinder, H.; Lohman, W.; Zhou, H.; Borst, H.

    2009-01-01

    A new engineering model for sound propagation in cities is presented. The model is based on numerical and experimental studies of sound propagation between street canyons. Multiple reflections in the source canyon and the receiver canyon are taken into account in an efficient way, while weak

  13. OMNIDIRECTIONAL SOUND SOURCE

    DEFF Research Database (Denmark)

    1996-01-01

    A sound source comprising a loudspeaker (6) and a hollow coupler (4) with an open inlet which communicates with and is closed by the loudspeaker (6) and an open outlet, said coupler (4) comprising rigid walls which cannot respond to the sound pressures produced by the loudspeaker (6). According...

  14. Breaking the Sound Barrier

    Science.gov (United States)

    Brown, Tom; Boehringer, Kim

    2007-01-01

    Students in a fourth-grade class participated in a series of dynamic sound learning centers followed by a dramatic capstone event--an exploration of the amazing Trashcan Whoosh Waves. It's a notoriously difficult subject to teach, but this hands-on, exploratory approach ignited student interest in sound, promoted language acquisition, and built…

  15. Notes on Sound

    Directory of Open Access Journals (Sweden)

    Bonnie Jones

    2012-08-01

    Full Text Available Bonnie Jones creates improvised and composed text-sound performances that explore the fluidity and function of electronic noise (field recordings, circuit bending and text (poetry, found, spoken. She is interested in how people perceive, “read” and interact with these sounds and texts given our current technological moment.

  16. NASA's Bio-Inspired Acoustic Absorber Concept

    Science.gov (United States)

    Koch, L. Danielle

    2017-01-01

    Transportation noise pollutes our worlds cities, suburbs, parks, and wilderness areas. NASAs fundamental research in aviation acoustics is helping to find innovative solutions to this multifaceted problem. NASA is learning from nature to develop the next generation of quiet aircraft.The number of road vehicles and airplanes has roughly tripled since the 1960s. Transportation noise is audible in nearly all the counties across the US. Noise can damage your hearing, raise your heart rate and blood pressure, disrupt your sleep, and make communication difficult. Noise pollution threatens wildlife when it prevents animals from hearing prey, predators, and mates. Noise regulations help drive industry to develop quieter aircraft. Noise standards for aircraft have been developed by the International Civil Aviation Organization and adopted by the US Federal Aviation Administration. The US National Park Service is working with the Federal Aviation Administration to try to balance the demand for access to the parks and wilderness areas with preservation of the natural soundscape. NASA is helping by conceptualizing quieter, more efficient aircraft of the future and performing the fundamental research to make these concepts a reality someday. Recently, NASA has developed synthetic structures that can absorb sound well over a wide frequency range, and particularly below 1000 Hz, and which mimic the acoustic performance of bundles of natural reeds. We are adapting these structures to control noise on aircraft, and spacecraft. This technology might be used in many other industrial or architectural applications where acoustic absorbers have tight constraints on weight and thickness, and may be exposed to high temperatures or liquids. Information about this technology is being made available through reports and presentations available through the NASA Technical Report Server, http:ntrs.nasa.gov. Organizations who would like to collaborate with NASA or commercialize NASAs technology

  17. Seismic and Biological Sources of Ambient Ocean Sound

    Science.gov (United States)

    Freeman, Simon Eric

    . This distribution of sources could reveal small-scale spatial ecological limitations, such as the availability of food and shelter. While array-based passive acoustic sensing is well established in seismoacoustics, the technique is little utilized in the study of ambient biological sound. With the continuance of Moore's law and advances in battery and memory technology, inferring biological processes from ambient sound may become a more accessible tool in underwater ecological evaluation and monitoring.

  18. Waveform analysis of sound

    CERN Document Server

    Tohyama, Mikio

    2015-01-01

    What is this sound? What does that sound indicate? These are two questions frequently heard in daily conversation. Sound results from the vibrations of elastic media and in daily life provides informative signals of events happening in the surrounding environment. In interpreting auditory sensations, the human ear seems particularly good at extracting the signal signatures from sound waves. Although exploring auditory processing schemes may be beyond our capabilities, source signature analysis is a very attractive area in which signal-processing schemes can be developed using mathematical expressions. This book is inspired by such processing schemes and is oriented to signature analysis of waveforms. Most of the examples in the book are taken from data of sound and vibrations; however, the methods and theories are mostly formulated using mathematical expressions rather than by acoustical interpretation. This book might therefore be attractive and informative for scientists, engineers, researchers, and graduat...

  19. InfoSound

    DEFF Research Database (Denmark)

    Sonnenwald, Diane H.; Gopinath, B.; Haberman, Gary O.

    1990-01-01

    The authors explore ways to enhance users' comprehension of complex applications using music and sound effects to present application-program events that are difficult to detect visually. A prototype system, Infosound, allows developers to create and store musical sequences and sound effects...... with application events, and have real-time, continuous auditory control of sounds during application execution. InfoSound has been used to create auditory interfaces for two applications: a telephone network service simulation and a parallel computation simulation. The auditory interfaces in these applications...... helped users detect rapid, multiple-event sequences that were difficult to visually detect using text and graphical interfaces. The authors describe the architecture of InfoSound, the use of the system, and the lessons learned....

  20. Sound classification of dwellings

    DEFF Research Database (Denmark)

    Rasmussen, Birgit

    2012-01-01

    National schemes for sound classification of dwellings exist in more than ten countries in Europe, typically published as national standards. The schemes define quality classes reflecting different levels of acoustical comfort. Main criteria concern airborne and impact sound insulation between...... dwellings, facade sound insulation and installation noise. The schemes have been developed, implemented and revised gradually since the early 1990s. However, due to lack of coordination between countries, there are significant discrepancies, and new standards and revisions continue to increase the diversity...... is needed, and a European COST Action TU0901 "Integrating and Harmonizing Sound Insulation Aspects in Sustainable Urban Housing Constructions", has been established and runs 2009-2013, one of the main objectives being to prepare a proposal for a European sound classification scheme with a number of quality...

  1. Plasmonic titanium nitride nanostructures for perfect absorbers

    DEFF Research Database (Denmark)

    Guler, Urcan; Li, Wen-Wei; Kinsey, Nathaniel

    2013-01-01

    We propose a metamaterial based perfect absorber in the visible region, and investigate the performance of titanium nitride as an alternative plasmonic material. Numerical and experimental results reveal that titanium nitride performs better than gold as a plasmonic absorbing material...

  2. The influence of sea ice, wind speed and marine mammals on Southern Ocean ambient sound

    Science.gov (United States)

    Menze, Sebastian; Zitterbart, Daniel P.; van Opzeeland, Ilse; Boebel, Olaf

    2017-01-01

    This paper describes the natural variability of ambient sound in the Southern Ocean, an acoustically pristine marine mammal habitat. Over a 3-year period, two autonomous recorders were moored along the Greenwich meridian to collect underwater passive acoustic data. Ambient sound levels were strongly affected by the annual variation of the sea-ice cover, which decouples local wind speed and sound levels during austral winter. With increasing sea-ice concentration, area and thickness, sound levels decreased while the contribution of distant sources increased. Marine mammal sounds formed a substantial part of the overall acoustic environment, comprising calls produced by Antarctic blue whales (Balaenoptera musculus intermedia), fin whales (Balaenoptera physalus), Antarctic minke whales (Balaenoptera bonaerensis) and leopard seals (Hydrurga leptonyx). The combined sound energy of a group or population vocalizing during extended periods contributed species-specific peaks to the ambient sound spectra. The temporal and spatial variation in the contribution of marine mammals to ambient sound suggests annual patterns in migration and behaviour. The Antarctic blue and fin whale contributions were loudest in austral autumn, whereas the Antarctic minke whale contribution was loudest during austral winter and repeatedly showed a diel pattern that coincided with the diel vertical migration of zooplankton.

  3. Evaluation of a Single-Beam Sonar System to Map Seagrass at Two Sites in Northern Puget Sound, Washington

    Science.gov (United States)

    Stevens, Andrew W.; Lacy, Jessica R.; Finlayson, David P.; Gelfenbaum, Guy

    2008-01-01

    Seagrass at two sites in northern Puget Sound, Possession Point and nearby Browns Bay, was mapped using both a single-beam sonar and underwater video camera. The acoustic and underwater video data were compared to evaluate the accuracy of acoustic estimates of seagrass cover. The accuracy of the acoustic method was calculated for three classifications of seagrass observed in underwater video: bare (no seagrass), patchy seagrass, and continuous seagrass. Acoustic and underwater video methods agreed in 92 percent and 74 percent of observations made in bare and continuous areas, respectively. However, in patchy seagrass, the agreement between acoustic and underwater video was poor (43 percent). The poor agreement between the two methods in areas with patchy seagrass is likely because the two instruments were not precisely colocated. The distribution of seagrass at the two sites differed both in overall percent vegetated and in the distribution of percent cover versus depth. On the basis of acoustic data, seagrass inhabited 0.29 km2 (19 percent of total area) at Possession Point and 0.043 km2 (5 percent of total area) at the Browns Bay study site. The depth distribution at the two sites was markedly different. Whereas the majority of seagrass at Possession Point occurred between -0.5 and -1.5 m MLLW, most seagrass at Browns Bay occurred at a greater depth, between -2.25 and -3.5 m MLLW. Further investigation of the anthropogenic and natural factors causing these differences in distribution is needed.

  4. Sound intensity probe for ultrasonic field in water using light-emitting diodes and piezoelectric elements

    Science.gov (United States)

    Zeng, Xi; Mizuno, Yosuke; Nakamura, Kentaro

    2017-12-01

    The sound intensity vector provides useful information on the state of an ultrasonic field in water, since sound intensity is a vector quantity expressing the direction and magnitude of the sound field. In the previous studies on sound intensity measurement in water, conventional piezoelectric sensors and metal cables were used, and the transmission distance was limited. A new configuration of a sound intensity probe suitable for ultrasonic measurement in water is proposed and constructed for trial in this study. The probe consists of light-emitting diodes and piezoelectric elements, and the output signals are transmitted through fiber optic cables as intensity-modulated light. Sound intensity measurements of a 26 kHz ultrasonic field in water are demonstrated. The difference in the intensity vector state between the water tank with and without sound-absorbing material on its walls was successfully observed.

  5. Piezooptic effect of absorbing environment

    Directory of Open Access Journals (Sweden)

    Ю. А. Рудяк

    2013-07-01

    Full Text Available Application of piezooptic effect of absorbing environment for the definition of the parameter of stress deformation state was examined. The analysis of dielectric permeability tensor of imaginary parts was done. It is shown that changes in the real part dielectric permeability tensor mainly the indicator of fracture was fixed by means of mechanics interference methods and the changes in the imaginary part (α – real rate of absorption can be measured by means of analysis of light absorption and thus stress deformation state can be determined

  6. Extending The Calibration In The Underwater Sound Reference Division (USRD) Reciprocity Coupler To Incorporate Phase

    Science.gov (United States)

    2016-09-01

    have a much higher impedance than the acoustic medium. 3. No air or any other low impedance material can be present in the coupler. The hydrophone...pressure ram controls the hydrostatic pressure in the coupler fluid, castor oil. Chamber temperature is controlled by heating or cooling distilled water...differential amplifier 4 USRD H48 Reciprocity Coupler 5 Ithaco 1201 6 NI BMC-2110 and NI-6259 7 Laptop Computer with Matlab 8 Pressure Ram 9 Neslab Endocal

  7. Acoustic Observatory Provides Real-Time Underwater Sounds from the Antarctic Ocean

    OpenAIRE

    Boebel, Olaf; Kindermann, Lars; Klinck, Holger; Bornemann, Horst; Plötz, Joachim; Steinhage, Daniel; Riedel, Sven; Burkhardt, Elke

    2006-01-01

    To obtain real-time, year-round acoustic data from the coastal Antarctic Ocean, an autonomous listening station, PALAOA (PerenniAL Acoustic Observatory in the Antarctic Ocean, or Hawaiian whale), was constructed in austral summer 2005/06, 15 km North of the German Neumayer Base. PALAOAs design was guided by demanding prerequisites: perennial, 365/24, autonomous operation, real-time data access, and full frequency and dynamic coverage. The station is located at 70°31S 8°13W, on the Ekström ice...

  8. Effects of Environmental Variability on Long-Range Underwater Sound Propagation: Mode Processing of LOAPEX

    Science.gov (United States)

    2011-05-01

    the ocean has been developed (together with T. Duda). Large changes in upper- ocean absorption coefficient predicted to follow carbon dioxide uptake...existing theory to the environments with strong range dependence. In addition, a study of oceanic acoustic response to acidification has been made...implementation. The second paper is a study of ambient noise level change in the ocean due to acidification . Also two papers devoted to the modal analysis

  9. Sound absorption of tropical woods and their radiation-induced composites

    International Nuclear Information System (INIS)

    Chia, L.H.L.; Teoh, S.H.; Tharmaratnam, K.; Tan, L.C.

    1988-01-01

    This is a preliminary study on the sound absorption properties of two tropical hardwoods, Light Red Meranti and Ramin, and their wood-polymer composites. Sound absorption is measured using a standing wave apparatus. The samples are of one thickness (7 mm) and cut longitudinally. Wood-polymer composites are made by impregnating the samples with methyl methacrylate which is polymerized in situ through γ-irradiation. Both woods and their composites are better sound absorbers at higher sound frequencies. With partial impregnation, the absorption coefficients are improved upon particularly in the region between 1-3 kHz. (author)

  10. Autonomous Underwater Vehicle Magnetic Mapping System

    Science.gov (United States)

    Steigerwalt, R.; Johnson, R. M.; Trembanis, A. C.; Schmidt, V. E.; Tait, G.

    2012-12-01

    An Autonomous Underwater Vehicle (AUV) Magnetic Mapping (MM) System has been developed and tested for military munitions detection as well as pipeline locating, wreck searches, and geologic surveys in underwater environments. The system is comprised of a high sensitivity Geometrics G-880AUV cesium vapor magnetometer integrated with a Teledyne-Gavia AUV and associated Doppler enabled inertial navigation further utilizing traditional acoustic bathymetric and side scan imaging. All onboard sensors and associated electronics are managed through customized crew members to autonomously operate through the vehicles primary control module. Total field magnetic measurements are recorded with asynchronous time-stamped data logs which include position, altitude, heading, pitch, roll, and electrical current usage. Pre-planned mission information can be uploaded to the system operators to define data collection metrics including speed, height above seafloor, and lane or transect spacing specifically designed to meet data quality objectives for the survey. As a result of the AUVs modular design, autonomous navigation and rapid deployment capabilities, the AUV MM System provides cost savings over current surface vessel surveys by reducing the mobilization/demobilization effort, thus requiring less manpower for operation and reducing or eliminating the need for a surface support vessel altogether. When the system completes its mission, data can be remotely downloaded via W-LAN and exported for use in advanced signal processing platforms. Magnetic compensation software has been concurrently developed to accept electrical current measurements directly from the AUV to address distortions from permanent and induced magnetization effects on the magnetometer. Maneuver and electrical current compensation terms can be extracted from the magnetic survey missions to perform automated post-process corrections. Considerable suppression of system noise has been observed over traditional

  11. Underwater Animal Monitoring Magnetic Sensor System

    KAUST Repository

    Kaidarova, Altynay

    2017-10-01

    Obtaining new insights into the behavior of free-living marine organisms is fundamental for conservation efforts and anticipating the impact of climate change on marine ecosystems. Despite the recent advances in biotelemetry, collecting physiological and behavioral parameters of underwater free-living animals remains technically challenging. In this thesis, we develop the first magnetic underwater animal monitoring system that utilizes Tunnel magnetoresistance (TMR) sensors, the most sensitive solid-state sensors today, coupled with flexible magnetic composites. The TMR sensors are composed of CoFeB free layers and MgO tunnel barriers, patterned using standard optical lithography and ion milling procedures. The short and long-term stability of the TMR sensors has been studied using statistical and Allan deviation analysis. Instrumentation noise has been reduced using optimized electrical interconnection schemes. We also develop flexible NdFeB-PDMS composite magnets optimized for applications in corrosive marine environments, and which can be attached to marine animals. The magnetic and mechanical properties are studied for different NdFeB powder concentrations and the performance of the magnetic composites for different exposure times to sea water is systematically investigated. Without protective layer, the composite magnets loose more than 50% of their magnetization after 51 days in seawater. The durability of the composite magnets can be considerably improved by using polymer coatings which are protecting the composite magnet, whereby Parylene C is found to be the most effective solution, providing simultaneously corrosion resistance, flexibility, and enhanced biocompatibility. A Parylene C film of 2μm thickness provides the sufficient protection of the magnetic composite in corrosive aqueous environments for more than 70 days. For the high level performance of the system, the theoretically optimal position of the composite magnets with respect to the sensing

  12. Digitizing a sound archive

    DEFF Research Database (Denmark)

    Cone, Louise

    2017-01-01

    In 1990 an artist by the name of William Louis Sørensen was hired by the National Gallery of Denmark to collect important works of art – made from sound. His job was to acquire sound art, but also recordings that captured rare artistic occurrences, music, performances and happenings from both...... Danish and international artists. His methodology left us with a large collection of unique and inspirational time-based media sound artworks that have, until very recently, been inaccessible. Existing on an array of different media formats, such as open reel tapes, 8-track and 4 track cassettes, VHS...

  13. Multi-channel coherent perfect absorbers

    KAUST Repository

    Bai, Ping

    2016-05-18

    The absorption efficiency of a coherent perfect absorber usually depends on the phase coherence of the incident waves on the surfaces. Here, we present a scheme to create a multi-channel coherent perfect absorber in which the constraint of phase coherence is loosened. The scheme has a multi-layer structure such that incident waves in different channels with different angular momenta can be simultaneously and perfectly absorbed. This absorber is robust in achieving high absorption efficiency even if the incident waves become "incoherent" and possess "random" wave fronts. Our work demonstrates a unique approach to designing highly efficient metamaterial absorbers. © CopyrightEPLA, 2016.

  14. Graphene based salisbury screen for terahertz absorber

    Science.gov (United States)

    Min Woo, Jeong; Kim, Min-Sik; Woong Kim, Hyun; Jang, Jae-Hyung

    2014-02-01

    A graphene-based, multiband absorber operating in terahertz (THz) frequency range was demonstrated. Graphene film was transferred onto the top of a flexible polymer substrate backed with a gold reflector. The graphene acts as a resistive film that partially attenuates and reflects THz waves. The destructive interference between THz waves reflected from graphene and backside reflector gives rise to perfect absorbance at multiple frequencies. To enhance the absorbance on/off ratio (AR), the conductivity of graphene was varied using a chemical doping method. The resulting p-doped, graphene-based THz absorber exhibited absorbance at maxima and AR higher than 0.95 and 25 dB, respectively.

  15. Prediction of Tonal Underwater Noise Pattern from Cavitating Propellers with Special Attention to Ice Cover Effects

    Directory of Open Access Journals (Sweden)

    Streckwall Heinrich

    2015-01-01

    Full Text Available To predict underwater noise spectra associated to regular occurrence of propeller cavitation we have extended an existing method [1] (used for the prediction of fluctuating hull pressures to become applicable for effects that are linked to a finite speed of sound. In [2] an intermediate approach was realized where (besides the hull far field boundaries were introduced but the incompressible flow assumption was kept. However compressibility effects become noticeable in the far field, which may be judged to start at some 2-3 propeller-diameters distance from the centre of the cavitation events, if we confine to emissions at 1st-4th blade frequency. It was a logical continuation of our former efforts to realize a compressible flow model and integrate the propeller as a noise source. Having increased the functionality of our approach by referencing the speed of sound, the precision of the method was also somehow reduced. In our former approach, like in comparable approaches (see for instance [3] and [4], the singularity system generating the near field propeller induced pressures involved various sources and vortices distributed on the propeller blades. With our current compressible approach this complexity was dropped, as a single point source substitutes the cavitating propeller. Such a simplification correlates with the assumption, that the monopole character of a noise source is decisive for the far field noise levels. In this contribution we outline the steps characterizing the procedure for predicting tonal underwater noise from cavitating propellers. In the first step a Vortex Lattice Method (VLM is used to access the cavitation pattern on the propeller with special focus on the cavity volume attached to one blade. The second step accumulates the distributed cavities to establish a fluctuating point source of equivalent far field noise characteristic. As relevant limits the hull, the free surface, the sea bottom and an ice cover are

  16. Into the sounding environment A compositional approach

    OpenAIRE

    Tzedaki, Aikaterini

    2012-01-01

    The focus of the compositional approach presented in this folio is the sounding environment. The term sounding environment is used in this context to refer to the whole of our living experience in the world which we might register as relating to sound. It might include everything that is sounding, seemingly sounding, imagined sounding, remembered sounding, sensed as sounding, composed to sound. It includes thus the actual sound environment, all that is sensed or interpreted as sound and imagi...

  17. A Framework for Evaluating Advanced Search Concepts for Multiple Autonomous Underwater Vehicle (AUV) Mine Countermeasures (MCM)

    National Research Council Canada - National Science Library

    Gooding, Trent

    2001-01-01

    .... In recent years, autonomous underwater vehicles (AUV) have emerged as a viable technology for conducting underwater search, survey, and clearance operations in support of the mine countermeasures (MCM) mission...

  18. A comparative view of routing protocols for underwater wireless sensor networks

    NARCIS (Netherlands)

    Bayrakdar, Y.; Meratnia, Nirvana; Kantarci, Aylin

    2011-01-01

    Design of efficient routing protocols for underwater sensor networks is challenging because of the distinctive characteristics of the water medium. Currently, many routing protocols are available for terrestrial wireless sensor networks. However, specific properties of underwater medium such as

  19. US-Japan Cooperative Research on Biology-Inspired Precision Maneuvering of Underwater Vehicles

    National Research Council Canada - National Science Library

    Kato, Naomi

    2004-01-01

    .... We constructed an underwater vehicle equipped with two pairs of mechanical pectoral fins and pectoral fin controllers to examine the swimming performance of the underwater vehicle in still water...

  20. Predictive Model for the Analysis of the Effects of Underwater Impulsive Sources on Marine Life

    National Research Council Canada - National Science Library

    Lazauski, Colin J

    2007-01-01

    A method is provided to predict the biological consequences to marine animals from exposure to multiple underwater impulsive sources by simulating underwater explosions over a defined period of time...