Sample records for active noise control

  1. Active control of the noise

    The problems of acoustic noise are more and more preponderant in the measure in that the amount of equipment and industrial machinery is increased such as fans, transformers, compressors etc. the use of devices passive mechanics for the reduction of the noise is effective and very appreciated because its effects embrace a wide range of acoustic frequency. However, to low frequencies, such devices become too big and expensive besides that present a tendency to do not effective. The control of active noise, CAN, using the electronic generation anti-noise, constitutes an interesting solution to the problem because their operation principle allows achieving an appreciable reduction of the noise by means of the use of compact devices. The traditional techniques for the control of acoustic noise like barriers and silenced to attenuate it, are classified as passive and their works has been accepted as norm as for the treatment of problems of noise it refers. Such techniques are considered in general very effective in the attenuation of noise of wide band. However, for low frequency, the required passive structures are too big and expensive; also, their effectiveness diminishes flagrantly, that which makes them impractical in many applications. The active suppression is profiled like a practical alternative for the reduction of acoustic noise. The idea in the active treatment of the noise it contemplates the use of a device electro-acoustic, like a speaker for example that it cancels to the noise by the generation of sounds of Same width and of contrary phase (anti-noise). The cancellation phenomenon is carried out when the ant-noise combines acoustically with the noise, what is in the cancellation of both sounds. The effectiveness of the cancellation of the primary source of noise depends on the precision with which the width and the phase of the generated ant-noise are controlled. The active control of noise, ANC (activates noise control), it is being investigated for

  2. Adaptive feedback active noise control

    Kuo, Sen M.; Vijayan, Dipa

    Feedforward active noise control (ANC) systems use a reference sensor that senses a reference input to the controller. This signal is assumed to be unaffected by the secondary source and is a good measure of the undesired noise to be cancelled by the system. The reference sensor may be acoustic (e.g., microphone) or non-acoustic (e.g., tachometer, optical transducer). An obvious problem when using acoustic sensors is that the reference signal may be corrupted by the canceling signal generated by the secondary source. This problem is known as acoustic feedback. One way of avoiding this is by using a feedback active noise control (FANC) system which dispenses with the reference sensor. The FANC technique originally proposed by Olson and May employs a high gain negative feedback amplifier. This system suffered from the drawback that the error microphone had to be placed very close to the loudspeaker. The operation of the system was restricted to low frequency range and suffered from instability due to the possibility of positive feedback. Feedback systems employing adaptive filtering techniques for active noise control were developed. This paper presents the FANC system modeled as an adaptive prediction scheme.

  3. Active Noise Control in Propeller Aircraft

    Johansson, Sven; Claesson, Ingvar


    A noisy environment dominated by low frequency noise can often be improved through the use of active noise control. This situation arises naturally in propeller aircraft where the propellers induce periodic low frequency noise inside the cabin. The cabin noise is typically rather high, and the passenger flight comfort could be improved considerably if this level were significantly reduced. This paper addresses same design aspects for multiple-reference active noise control systems based on th...

  4. Active Noise Control in Forest Machines

    Forsgren, Fredrik


    Achieving a low noise level is of great interest to the forest machine industry. Traditionally this is obtained by using passive noise reduction, i.e. by using materials for sound isolation and sound absorption. Especially designs to attenuate low frequency noise tend to be bulky and impractical from an installation point of view. An alternative solution to the problem is to use active noise control (ANC). The basic principle of ANC is to generate an anti-noise signal designed to destructivel...

  5. Development of Active Noise Control System for Quieting Transformer Noise

    Lee, Bok Kyu; Song, Seik Young; Choi, Huo Yul [Korea Electric Power Research Institute, Taejon (Korea, Republic of); Yun, Dae Hea; Lee, Hyuk Jae [Korea Electrotechnology Research Institute, Changwon (Korea, Republic of)


    The passive noise control technique made use of sound-absorbing or soundproofing materials, so it required a large area and high cost for installation and had a drawback of poor performance at low frequency. Compared to this, the Active Noise Control attenuates noise sound pressure by using secondary source which has same performance ay low-frequency. Furthermore, it is able to save space and expenses. - research on adaptive algorithms - evaluation of global attenuation of the control - computer simulation - real-time Active Noise Control System Hardware Implementation - ANC system setting in the noisy area.

  6. Active Noise Control for Vehicle Exhaust Noise Reduction

    李克强; 杨殿阁; 郑四发; 连小珉; 田中丈晴


    An active noise control (ANC) method was developed for exhaust noise reduction for medium-duty diesel trucks. A modified variable step size least mean squares (LMS) algorithm was used for the controller in a variable environment that considered the vehicle's acceleration characteristics. The variable step size time-based synchronized filtered-x LMS method (SFX-TB) used an adaptive algorithm that was more efficient than the conventional filtered-x LMS algorithm. The simulation and the experimental tests show that the control trackability and stability provided by the algorithm during acceleration enable the ANC system to effectively reduce the vehicle exhaust noise.

  7. Active Control of Fan Noise

    Nobuhiko YAMASAKI; Hirotoshi TAJIMA


    In the wake-rotor interaction fan noise, a number of the interacting modes at the blade passing frequency (BPF)and its harmonics are generated which are prescribed by the number of stator and rotor blades etc. In the present study, the dominant mode is tried to be suppressed by the secondary sound from the loudspeaker actuators. One of the novel features of the present system is the adoption of the control board with the Field Programmable Gate Array (FPGA) hardware and the LabVIEW software to synchronize the circumferentially installed loudspeaker actuators with the relative location of rotational blades under arbitrary fan rotational speeds. The experiments were conducted under the conditions of three rotational speeds of 2004, 3150, and 4002 [rpm]. The reduction in the sound pressure level (SPL) was observed for all three rotational speeds. The sound pressure level at the BPF was reduced approximately 13 [dB] for 2004 [rpm] case, but not so large reduction was attained for other cases probably due to the inefficiency of the loudspeaker actuators at high frequencies

  8. Active noise control for high frequencies

    Kaymak, E; Atherton, MA; Rotter, KRG; Millar, B.


    There are many applications that can benefit from Active Noise Control (ANC) such as in aircraft cabins and air conditioning ducts, i.e. in situations where technology interferes with human hearing in a harmful way or disrupts communication. Headsets with analogue ANC circuits have been used in the armed forces for attenuating frequencies below 1 kHz, which when combined with passive filtering offers protection across the whole frequency range of human hearing. A dental surgery is also a nois...

  9. Recent advances in active control of aircraft cabin noise

    Mathur, Gopal; Fuller, Christopher


    Active noise control techniques can provide significant reductions in aircraft interior noise levels without the structural modifications or weight penalties usually associated with passive techniques, particularly for low frequency noise. Our main objective in this presentation is to give a review of active control methods and their applications to aircraft cabin noise reduction with an emphasis on recent advances and challenges facing the noise control engineer in the practical application of these techniques. The active noise control method using secondary acoustic sources, e.g., loudspeakers, as control sources for tonal noise reduction is first discussed with results from an active noise control flight test demonstration. An innovative approach of applying control forces directly to the fuselage structure using piezoelectric actuators, known as active structural acoustic control (ASAC), to control cabin noise is then presented. Experimental results from laboratory ASAC tests conducted on a full-scale fuselage and from flight tests on a helicopter will be discussed. Finally, a hybrid active/passive noise control approach for achieving significant broadband noise reduction will be discussed. Experimental results of control of broadband noise transmission through an aircraft structure will be presented.

  10. Active Noise Control of the Heavy Truck Interior Cab


    In order to control the noise of the heavy truck interior cab effectively, the active noise control methods are employed. First, an interior noise field test for the heavy truck is performed, and frequencies of interior noise of this vehicle are analyzed. According to the spectrum analysis of acquired noise signal, it is found out that the main frequencies of interior noise are less than 800Hz. Then the least squares lattice (LSL) algorithm is used as signal processing algorithm of the controller and a closed-loop control DSP system, based on TMS 320VC5416, is developed. The residual signal at driver's ear is used as feedback signal. Lastly, the developed ANC system is loaded into the heavy truck cab, and controlling the noise at driver's ear for that truck at different driving speeds is attempted. The noise control test results indicate that the cab interior noise is reduced averagely by 0.9 dBA at different driving speeds.

  11. Perception Neural Networks for Active Noise Control Systems

    Wang Xiaoli


    Full Text Available In a response to a growing demand for environments of 70dB or less noise levels, many industrial sectors have focused with some form of noise control system. Active noise control (ANC has proven to be the most effective technology. This paper mainly investigates application of neural network on self-adaptation system in active noise control (ANC. An active silencing control system is made which adopts a motional feedback loudspeaker as not a noise controlling source but a detecting sensor. The working fundamentals and the characteristics of the motional feedback loudspeaker are analyzed in detail. By analyzing each acoustical path, identification based adaptive linear neural network is built. This kind of identifying method can be achieved conveniently. The estimated result of each sound channel matches well with its real sound character, respectively.

  12. Active Control of Aerodynamic Noise Sources

    Reynolds, Gregory A.


    Aerodynamic noise sources become important when propulsion noise is relatively low, as during aircraft landing. Under these conditions, aerodynamic noise from high-lift systems can be significant. The research program and accomplishments described here are directed toward reduction of this aerodynamic noise. Progress toward this objective include correction of flow quality in the Low Turbulence Water Channel flow facility, development of a test model and traversing mechanism, and improvement of the data acquisition and flow visualization capabilities in the Aero. & Fluid Dynamics Laboratory. These developments are described in this report.

  13. Active Noise Control Experiments using Sound Energy Flu

    Krause, Uli


    This paper reports on the latest results concerning the active noise control approach using net flow of acoustic energy. The test set-up consists of two loudspeakers simulating the engine noise and two smaller loudspeakers which belong to the active noise system. The system is completed by two acceleration sensors and one microphone per loudspeaker. The microphones are located in the near sound field of the loudspeakers. The control algorithm including the update equation of the feed-forward controller is introduced. Numerical simulations are performed with a comparison to a state of the art method minimising the radiated sound power. The proposed approach is experimentally validated.

  14. Active noise control in fuselage design

    Krakers, L.A.; Tooren, M.J.L. van; Beukers, A.; Berkhof, A.P.; Goeje, M.P. de


    To achieve comfortable noise levels inside the passenger cabin, sound damping measures have to be taken to improve the sound insulation properties of the bare airframe. Usually the sound insulation requirements of a passenger cabin are met after the mechanical design of the fuselage structure is alr

  15. Development of a Voice Activity Controlled Noise Canceller

    Aini Hussain


    Full Text Available In this paper, a variable threshold voice activity detector (VAD is developed to control the operation of a two-sensor adaptive noise canceller (ANC. The VAD prohibits the reference input of the ANC from containing some strength of actual speech signal during adaptation periods. The novelty of this approach resides in using the residual output from the noise canceller to control the decisions made by the VAD. Thresholds of full-band energy and zero-crossing features are adjusted according to the residual output of the adaptive filter. Performance evaluation of the proposed approach is quoted in terms of signal to noise ratio improvements as well mean square error (MSE convergence of the ANC. The new approach showed an improved noise cancellation performance when tested under several types of environmental noise. Furthermore, the computational power of the adaptive process is reduced since the output of the adaptive filter is efficiently calculated only during non-speech periods.

  16. Active structural acoustic control of aircraft interior flow noise via the use of active trim panels

    Mahnken, Brian W.


    Modem jet aircraft interior noise can be categorized into two main types: tonal noise caused by engine imbalance or blade passage, and mid frequency broadband noise resulting from turbulent flow. This project addresses aircraft interior flow noise caused by a flow separation over the crown of the aircraft. The noise control approach is to mount piezoelectric actuators to the aircraft interior cockpit crown trim panel and use them to actively control aircraft interior noise with...

  17. Applications of active adaptive noise control to jet engines

    Shoureshi, Rahmat; Brackney, Larry


    During phase 2 research on the application of active noise control to jet engines, the development of multiple-input/multiple-output (MIMO) active adaptive noise control algorithms and acoustic/controls models for turbofan engines were considered. Specific goals for this research phase included: (1) implementation of a MIMO adaptive minimum variance active noise controller; and (2) turbofan engine model development. A minimum variance control law for adaptive active noise control has been developed, simulated, and implemented for single-input/single-output (SISO) systems. Since acoustic systems tend to be distributed, multiple sensors, and actuators are more appropriate. As such, the SISO minimum variance controller was extended to the MIMO case. Simulation and experimental results are presented. A state-space model of a simplified gas turbine engine is developed using the bond graph technique. The model retains important system behavior, yet is of low enough order to be useful for controller design. Expansion of the model to include multiple stages and spools is also discussed.

  18. Active control of road booming noise in automotive interiors.

    Oh, Shi-Hwan; Kim, Hyoun-suk; Park, Youngjin


    An active feedforward control system has been developed to reduce the road booming noise that has strong nonlinear characteristics. Four acceleration transducers were attached to the suspension system to detect reference vibration and two loudspeakers were used to attenuate the noise near the headrests of two front seats. A leaky constraint multiple filtered-X LMS algorithm with an IIR-based filter that has fast convergence speed and frequency selective controllability was proposed to increase the control efficiency in computing power and memory usage. During the test drive on the rough asphalt and turtle-back road at a constant speed of 60 km/h, we were able to achieve a reduction of around 6 dB of A-weighted sound pressure level in the road booming noise range with the proposed algorithm, which could not be obtained with the conventional multiple filtered-X LMS algorithm. PMID:11831793

  19. Active Flow Effectors for Noise and Separation Control

    Turner, Travis L.


    New flow effector technology for separation control and enhanced mixing is based upon shape memory alloy hybrid composite (SMAHC) technology. The technology allows for variable shape control of aircraft structures through actively deformable surfaces. The flow effectors are made by embedding shape memory alloy actuator material in a composite structure. When thermally actuated, the flow effector def1ects into or out of the flow in a prescribed manner to enhance mixing or induce separation for a variety of applications, including aeroacoustic noise reduction, drag reduction, and f1ight control. The active flow effectors were developed for noise reduction as an alternative to fixed-configuration effectors, such as static chevrons, that cannot be optimized for airframe installation effects or variable operating conditions and cannot be retracted for off-design or fail-safe conditions. Benefits include: Increased vehicle control, overall efficiency, and reduced noise throughout all f1ight regimes, Reduced flow noise, Reduced drag, Simplicity of design and fabrication, Simplicity of control through direct current stimulation, autonomous re sponse to environmental heating, fast re sponse, and a high degree of geometric stability. The concept involves embedding prestrained SMA actuators on one side of the chevron neutral axis in order to generate a thermal moment and def1ect the structure out of plane when heated. The force developed in the host structure during def1ection and the aerodynamic load is used for returning the structure to the retracted position. The chevron design is highly scalable and versatile, and easily affords active and/or autonomous (environmental) control. The technology offers wide-ranging market applications, including aerospace, automotive, and any application that requires flow separation or noise control.

  20. The passive and active noise control strategy in the aircraft interior noise

    Paonessa, A.


    The stringent comfort requirements that the airliners are providing to the aircraft manufacturers, also for the small regional commuter are increasing the attention of the aircraft designer to the aircraft interior noise performance. The research on the design methodologies is very much improved in the last years providing new materials and new system like the active noise control usefull to get a more comfortable interior and achieve a large competition on the market. In this paper a general...

  1. Implementation Considerations for Active Noise Control in Ventilation Systems

    Asteborg, Marcus; Svanberg, Niklas


    The most common method to attenuate noise in ventilation systems today is passive silencers. For these to efficiently attenuate frequencies below 400 Hz such silencers need to be large and a more neat solution to attenuate low frequencies is to use active noise control (ANC). The usage of ANC in ventilation systems is well known and there are several commercial products available. ANC is not, however, used on a wide basis due to its often high price and poor performance. Since the price is an...

  2. Application of Adaptive Filters to Active Noise Control

    PEI Bingnan; LI Chuanguang


    A modified LMS algorithm for noise-control is suggested after a mathematical model ofsound-cancellation is established, on the basis of thesound wave interference principle and the physicalmodel of progressive waves in a duct. Its applicationin controlling noise with the frequency range from 100to 800 Hz can be implemented by using the adaptivedigital signal processing technique. The experimentson a pink noise, a broadband noise and a noise takenfrom a tank were made, which show that there existsan attenuation of 11 dB at the frequency of 500 Hzor so, and that the proposed adaptive noise controltechnique is very effective and valid.

  3. Sound quality of low-frequency and car engine noises after active noise control

    Gonzalez, A.; Ferrer, M.; de Diego, M.; Piñero, G.; Garcia-Bonito, J. J.


    The ability of active noise control (ANC) systems to achieve a more pleasant sound has been evaluated by means of sound quality analysis of a real multi-channel active noise controller. Recordings of real car engine noises had been carried out using a Head acoustics TM binaural head simulator seated in a typical car seat, and these signals together with synthesized noise have been actively controlled in an enclosed room. The sound quality study has focused on the estimation of noise quality changes through the evaluation of the sense of comfort. Two methods have been developed: firstly, a predictive method based on psychoacoustic parameters (loudness, roughness, tonality and sharpness); and secondly, a subjective method using a jury test. Both results have been related to the spectral characteristics of the sounds before and after active control. It can be concluded from both analyses that ANC positively affects acoustic comfort. The engine noise mathematical comfort predictor is based on loudness and roughness (two psychoacoustic parameters directly influenced by ANC), and has satisfactorily predicted the improvements in the pleasantness of the sounds. As far as the subjective evaluation method is concerned, the jury test has showed that acoustic comfort is, in most cases, directly related to the sense of quietness. However, ANC has also been assessed negatively by the jury in the cases that it was unable to reduce the loudness, perhaps because of the low amplitudes of the original sounds. Finally, from what has been shown, it can be said that the subjective improvements strongly depends on the attenuation level achieved by the ANC system operation, as well as the spectral characteristics of the sounds before and after control.

  4. Active noise control to reduce the blade tone noise of centrifugal fans

    Koopmann, G. H.; Neise, W.; Chen, W.


    An active noise control method for suppressing the blade tones of centrifugal fans is presented which uses two secondary sound sources mounted into the cutoff region of the fan casing. Experiments were conducted for centrifugal fans with impeller diameters between 280 and 710 mm using two different designs for the secondary sources. The results indicate that the sound field inside the casing is dominated by the rotor locked pressure field, and that the blade tone noise measured in the far-field is generated by the unsteady pressures at the cutoff, which in turn are produced by the flow leaving the impeller.

  5. Smart materials and active noise and vibration control in vehicles

    Doppenberg, E.J.J.; Berkhoff, A.P.; Overbeek, M. van [TNO Institute of Applied Physics, Delft (Netherlands)


    Results are presented for the reduction of sound radiated from a structure using different control methodologies. Two approaches for active structural acoustic control are mentioned to reduce sound radiated by the structure: the acoustic approach or the vibro-acoustic approach. In both cases integrated actuators in structure materials are necessary to realise feasible products. Furthermore the development of an efficient shaker for Active Isolation techniques is described. The prototype of TNO TPD can produce a force of 400 N up to 250 Hz at a good performance-volume ratio. To enhance the robustness of the active control applications, the use of the subspace identification based control methods are developed. The robustness property of subspace identification methods forms the basis of an accurate model updating mechanism, using small size data batches. The performed simulations reveal excellent robustness performance under very general noise conditions or during operation of the control system. Furthermore the development of the techniques can be exploited to realise sound comfort requirements to enhance audible communications of vehicle related applications. To anticipate to these developments in the automotive industry, TNO has set up a Sound and Vibrations Research Centre with Twente University and a research program on Smart Panels with the Delft University. To investigate the potential markets and applications for sound comfort in the means of transportation, TNO-TPD and the Institute of Sound and Vibration Research in England (ISVR) have agreed on a cooperative venture to develop and realise 'active control of electroacoustics' (ACE). (orig.)

  6. Active Control of Fan Noise-Feasibility Study. Volume 1; Flyover System Noise Studies

    Kraft, Robert E.; Janardan, B. A.; Kontos, G. C.; Gliebe, P. R.


    A study has been completed to examine the potential reduction of aircraft flyover noise by the method of active noise control (ANC). It is assumed that the ANC system will be designed such that it cancels discrete tones radiating from the engine fan inlet or fan exhaust duct. Thus, without considering the engineering details of the ANC system design, tone levels are arbitrarily removed from the engine component noise spectrum and the flyover noise EPNL levels are compared with and without the presence of tones. The study was conducted for a range of engine cycles, corresponding to fan pressure ratios from 1.3 to 1.75. The major conclusions that can be drawn are that, for a fan pressure ratio of 1.75, ANC of tones gives about the same suppression as acoustic treatment without ANC, and for a fan pressure ratio of 1.45, ANC appears to offer less effectiveness than passive treatment. Additionally, ANC appears to be more effective at sideline and cutback conditions than at approach. Overall EPNL suppressions due to tone removal range from about 1 to 3 dB at takeoff engine speeds and from 1 to 5 db at approach speeds. Studies of economic impact of the installation of an ANC system for the four engine cases indicate increases of DOC ranging from 1 to 2 percent, favoring the lower fan pressure ratio engines. Further study is needed to confirm the results by examining additional engine data, particularly at low fan pressure ratios, and studying the details of the current results to obtain a more complete understanding. Further studies should also include determining the effects of combining passive and active treatment.

  7. Application of High Order X-LMS Filter for Active Noise Control



    Full Text Available In this paper active noise is controlled by using higher order X-LMS (least mean square filter. This technique is based on X-NLMS (normalized least mean square, also known as traditional acoustic noise cancellation (ANC scheme. It cancels the wideband noise from the corrupted speech signal. The active noise reducing headphone is probably the most successful application of active control of sound – the technology of cancelling sound with sound i.e., by using anti-noise signal. This report presents an outlined technical review of noise cancellation in headphones. The principles of passive noise attenuation are presented after which active attenuation is introduced showing how the two complement the attenuation performance. In real-time environment, the number of different applications in which adaptive techniques are being successfully used that are echo cancellation, equalization of dispersive channels, system identification, signal enhancement, noise cancelling and control.

  8. A study on transient enhancement for fault diagnosis based on an active noise control system

    Tian, X.; Gu, Fengshou; Zhen, Dong; Tran, Tung; Ball, Andrew


    Active noise control (ANC) is a more effective technique used for acoustic noise cancelation in comparison with passive approaches which are difficult and expensive to implement, especially for cancelling the noise in the low frequency range. In the ANC system, an anti-noise signal is introduced to suppress the primary noise to produce a residual which is used for updating the adaptive filter coefficients. In this paper, a method of transient content enhancement for fault detection and diagno...

  9. Foundations of Active Control - Active Noise Reduction Helmets

    Elmkjær, Torsten Haaber Leth


    regularization. A simplification of this algorithm leads to the MC-αγΠ-NLMS algorithm that is an extended variant of the NLMS algorithm. Off-line simultaneous system identification capabilities of a complex system involving a total 4 secondary paths, 20 feedback paths and 4 control-performance paths is...... obvious input and output channel definition by a finite lumped-elements multi-channel system. Usually, no unique transfer function x exist as the system is not point-wise excited, but excited over an area as in the case of diffuse sound field illumination. A new method for acoustical signal processing...

  10. Study of active noise control system for a commercial HVAC unit

    Devineni, Naga

    Acoustic noise is a common problem in everyday life. If the appliances that are present in the work and living areas generate noise then it's a serious problem. One such appliance is the Heating, Ventilation and Air-conditioning system (HVAC) in which blower fan and compressor units are housed together. Operation of a HVAC system creates two kinds of noise. One is the noise due to the air flow and the other is the result of the compressor. Both of them exhibit different signal properties and need different strategies to control them. There has been previous efforts in designing noise control systems that can control noise from the HVAC system. These include passive methods which use sound absorption materials to attenuate noise and active methods which cancel noise by generating anti-noise. Passive methods are effective in limiting the high frequency noise, but are inefficient in controlling low frequency noise from the compressor. Compressor noise is one of the strong low frequency components that propagate through the walls, therefore there is need for deploying active signal processing methods that consider the signal properties into consideration to cancel the noise acoustically. The quasi periodic nature of the compressor noise is exploited in noise modeling which aids in implementing an adaptive linear prediction filter in estimating the anti noise [12]. In this thesis, a multi channel architecture has been studied for a specific HVAC system in order to improve noise cancellation by creating larger quiet zone. In addition to the multi-channel architecture, a real time narrow band Active Noise Control (ANC) was employed to cancel noise under practical conditions.

  11. Application of High Order X-LMS Filter for Active Noise Control

    N.V.K.Mahalakshmi; Sindhu, D; B. Ranjith Kumar; N.Santhisri; G. Sowjanya Rao


    In this paper active noise is controlled by using higher order X-LMS (least mean square) filter. This technique is based on X-NLMS (normalized least mean square), also known as traditional acoustic noise cancellation (ANC) scheme. It cancels the wideband noise from the corrupted speech signal. The active noise reducing headphone is probably the most successful application of active control of sound – the technology of cancelling sound with sound i.e., by using anti-noise signal. This report p...

  12. Reduction of helicopter blade-vortex interaction noise by active rotor control technology

    Yu, Yung H.; Gmelin, Bernd; Splettstoesser, Wolf; Philippe, Jean J.; Prieur, Jean; Brooks, Thomas F.

    Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor blade-vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations.

  13. Reduction of Helicopter Blade-Vortex Interaction Noise by Active Rotor Control Technology

    Yu, Yung H.; Gmelin, Bernd; Splettstoesser, Wolf; Brooks, Thomas F.; Philippe, Jean J.; Prieur, Jean


    Helicopter blade-vortex interaction noise is one of the most severe noise sources and is very important both in community annoyance and military detection. Research over the decades has substantially improved basic physical understanding of the mechanisms generating rotor blade-vortex interaction noise and also of controlling techniques, particularly using active rotor control technology. This paper reviews active rotor control techniques currently available for rotor blade vortex interaction noise reduction, including higher harmonic pitch control, individual blade control, and on-blade control technologies. Basic physical mechanisms of each active control technique are reviewed in terms of noise reduction mechanism and controlling aerodynamic or structural parameters of a blade. Active rotor control techniques using smart structures/materials are discussed, including distributed smart actuators to induce local torsional or flapping deformations, Published by Elsevier Science Ltd.

  14. Active Control of Fan Noise: Feasibility Study. Volume 4; Flyover System Noise Studies

    Kraft, R. E.; Janardan, B. A.; Gliebe, P. R.; Kontos, G. C.


    An extension of a prior study has been completed to examine the potential reduction of aircraft flyover noise by the method of active noise control (ANC). It is assumed that the ANC system will be designed such that it cancels discrete tones radiating from the engine fan inlet or fan exhaust duct, at least to the extent that they no longer protrude above the surrounding broadband noise levels. Thus, without considering the engineering details of the ANC system design, tone levels am arbitrarily removed from the engine component noise spectrum and the flyover noise EPNL levels are compared with and without the presence of tones. The study was conducted for a range of engine cycles, corresponding to fan pressure ratios of 1.3, 1.45, 1.6, and 1.75. This report is an extension of an effort reported previously. The major conclusions drawn from the prior study, which was restricted to fan pressure ratios of 1.45 and 1.75, are that, for a fan pressure ratio of 1.75, ANC of tones gives about the same suppression as acoustic treatment without ANC. For a fan pressure ratio of 1.45, ANC appears to offer less effectiveness from passive treatment. In the present study, the other two fan pressure ratios are included in a more detailed examination of the benefits of the ANC suppression levels. The key results of this extended study are the following observations: (1) The maximum overall benefit obtained from suppression of BPF alone was 2.5 EPNdB at high fan speeds. The suppression benefit increases with increase in fan pressure ratio (FPR), (2) The maximum overall benefit obtained from suppression of the first three harmonics was 3 EPNdB at high speeds. Suppression benefit increases with increase in FPR, (3) At low FPR, only about 1.0 EPNdB maximum reduction was obtained. Suppression is primarily from reduction of BPF at high FPR values and from the combination of tones at low FPR, (4) The benefit from ANC is about the same as the benefit from passive treatment at fan pressure

  15. Time-domain versus frequency-domain effort weighting in active noise control

    Friot, Emmanuel


    Although Active Noise Control aims at reducing the noise at a set of error sensors, it is often designed by minimizing an error index that includes a weightedpenalty on the actuator inputs. In this way, the control tends to be more robust and the effort-weighting parameter allows the maximum voltages applied to the control sources to be monitored. Two similar effort-weighting techniques have been widely implemented in active control studies: optimal control can be computed using Tikhonov regu...

  16. Sequentially Adapted Parallel Feedforward Active Noise Control of Noisy Sinusoidal Signals

    Govind Kannan


    Full Text Available A large class of acoustic noise sources has an underlying periodic process that generates a periodic noise component, and thus their acoustic noise can in general be modeled as the sum of a periodic signal and a randomly fluctuating signal (usually a broadband background noise. Active control of periodic noise (i.e., for a mixture of sinusoids is more effective than that of random noise. For mixtures of sinusoids in a background broadband random noise, conventional FXLMS-based single filter method does not reach the maximum achievable Noise Attenuation Level (NALmax⁡. In this paper, an alternative approach is taken and the idea of a parallel active noise control (ANC architecture for cancelling mixtures of periodic and random signals is presented. The proposed ANC system separates the noise into periodic and random components and generates corresponding antinoises via separate noise cancelling filters, and tends to reach NALmax⁡ consistently. The derivation of NALmax⁡ is presented. Both the separation and noise cancellation are based on adaptive filtering. Experimental results verify the analytical development by showing superior performance of the proposed method, over the single-filter approach, for several cases of sinusoids in white noise.

  17. Active control of noise radiation from vibrating structures

    Mørkholt, Jakob

    The thesis is concerned with the active control of randomly vibrating structures by means of feedback control, with particular emphasis on reducing the sound radiation from such structures. A time domain model of the structural and radiation dynamics of an actively controlled plate has been...... developed, based on the theory of radiation filters for estimating the sound radiation from multimodal vibrations. This model has then been used in simulations of optimal feedback control, with special emphasis of the stability margins of the optimal control scheme. Two different methods of designing...

  18. A new approach to control noise from entertainment facilities: Active control and measurement of amplified community noise

    Peppin, Richard J.; Casamajó, Joan


    While traffic noise is perhaps the most pervasive of community noises, much of the contribution now comes from amplified sound: live music, discos, theme parks, and exercise studios. Those producing the sound or music want it loud and those not interested want to be protected against noise. Noise limits at the receiving or producing property line must be met for the minimum community acceptance. However the time-, and perhaps the spatially-, varying sound in entertainment facilities is often constantly modified (and maybe monitored) near the source of the sound. Hence it is hard to relate and to control the sound at the property line. This paper presents a unique noise control device. It is based on the octave band ``transfer function'' between the sound produced in the entertainment area and the noise received at the property line. The overall insulation can be measured and is input to the instrument. When a noise level limit is exceeded at the receiver, due to the amplified interior noise at the facility, the sound output of the device is automatically controlled to reduce the noise. The paper provides details of the design and possible abatement scenarios with examples.

  19. Smart Materials and Active Noise and Vibration Control in Vehicles

    Doppenberg, E.J.J.; Berkhoff, A.P.; Overbeek, van M.


    The paper presents the results for the reduction of sound radiated from a structure using different control methodologies, and discusses two approaches for active structural acoustic control: the acoustic approach or the vibro-acoustic approach. Integrated actuators in structure material are necessa

  20. Integration of Bass Enhancement and Active Noise Control System in Automobile Cabin

    Liang Wang


    Full Text Available With the advancement of digital signal processing technologies, consumers are more concerned with the quality of multimedia entertainment in automobiles. In order to meet this demand, an audio enhancement system is needed to improve bass reproduction and cancel engine noise in the cabins. This paper presents an integrated active noise control system that is based on frequency-sampling filters to track and extract the bass information from the audio signal, and a multifrequency active noise equalizer to tune the low-frequency engine harmonics to enhance the bass reproduction. In the noise cancellation mode, a maximum of 3 dB bass enhancement can be achieved with significant noise suppression, while higher bass enhancement can be achieved in the bass enhance mode. The results show that the proposed system is effective for solving both the bass audio reproduction and the noise control problems in automobile cabins.

  1. Active noise cancellation algorithms for impulsive noise

    Li, Peng; Yu, Xun


    Impulsive noise is an important challenge for the practical implementation of active noise control (ANC) systems. The advantages and disadvantages of popular filtered-X least mean square (FXLMS) ANC algorithm and nonlinear filtered-X least mean M-estimate (FXLMM) algorithm are discussed in this paper. A new modified FXLMM algorithm is also proposed to achieve better performance in controlling impulsive noise. Computer simulations and experiments are carried out for all three algorithms and th...

  2. The effect of structural-acoustic coupling on the active control of noise in vehicles

    Cheer, Jordan; Elliott, Stephen J.


    Active noise control systems offer a potential method of reducing the weight of passive acoustic treatment and, therefore, increasing vehicles’ fuel ef?ciency. These can be particularly cost-ef?cient if integrated with the entertainment system. A combined system is presented employing feedforward control of engine noise and feedback control of road noise, using a‘modal’ error signal. Due to the dependence of the feedback system on the modal response of the vehicle cabin, and the in?uence of s...

  3. Controlled Noise Seismology

    Hanafy, Sherif M.


    We use controlled noise seismology (CNS) to generate surface waves, where we continuously record seismic data while generating artificial noise along the profile line. To generate the CNS data we drove a vehicle around the geophone line and continuously recorded the generated noise. The recorded data set is then correlated over different time windows and the correlograms are stacked together to generate the surface waves. The virtual shot gathers reveal surface waves with moveout velocities that closely approximate those from active source shot gathers.

  4. Noise-driven activation in human intermittent control: a double-well potential model

    Zgonnikov, Arkady


    In controlling unstable systems humans switch intermittently between the passive and active behavior instead of controlling the system in a continuous manner. The notion of noise-driven control activation provides a richer alternative to the conventional threshold-based models of intermittent motor control. The present study represents the control activation as a random walk in a continuously changing double-well potential. The match between the proposed model and the previous data on human balancing of virtual stick prompts that the double-well approach can aid in explaining complex dynamics of human behavior in control processes.

  5. Source localization for active control of turbofan rotor-stator broadband noise

    Walker, Bruce E.


    In order to identify a reference signal source for an active noise cancellation system, cross-correlation techniques were used to localize broadband noise source regions on exit guide vanes of the NASA Glenn Research Center Advance Noise Control Fan (ANCF). Arrays of surface pressure sensors were imbedded in one guide vane and in the wall of the fan. Synchronous sampling was used with a multichannel data acquisition system to allow removal of periodic components from the signals. The signals were then cross-correlated to assess radiation directivity and the relationship between vane surface pressure and in-duct acoustic noise. The results of these measurements indicated that broadband unsteady pressures near the leading edge tip of the guide vane were well enough correlated with acoustic radiation that 2-3 dB active noise cancellation could be achieved using a simple gain-delay control algorithm and actuator array. After successful simulation in a wind tunnel environment the concept was incorporated on 15 guide vanes and tested in ANCF. Cross-correlation measurements were further used to evaluate system performance and to identify competing noises from rotating and stationary sources within the fan.

  6. Robust active noise control in the loadmaster area of a military transport aircraft.

    Kochan, Kay; Sachau, Delf; Breitbach, Harald


    The active noise control (ANC) method is based on the superposition of a disturbance noise field with a second anti-noise field using loudspeakers and error microphones. This method can be used to reduce the noise level inside the cabin of a propeller aircraft. However, during the design process of the ANC system, extensive measurements of transfer functions are necessary to optimize the loudspeaker and microphone positions. Sometimes, the transducer positions have to be tailored according to the optimization results to achieve a sufficient noise reduction. The purpose of this paper is to introduce a controller design method for such narrow band ANC systems. The method can be seen as an extension of common transducer placement optimization procedures. In the presented method, individual weighting parameters for the loudspeakers and microphones are used. With this procedure, the tailoring of the transducer positions is replaced by adjustment of controller parameters. Moreover, the ANC system will be robust because of the fact that the uncertainties are considered during the optimization of the controller parameters. The paper describes the necessary theoretic background for the method and demonstrates the efficiency in an acoustical mock-up of a military transport aircraft. PMID:21568404

  7. Active control of noise on the source side of a partition to increase its sound isolation

    Tarabini, Marco; Roure, Alain; Pinhede, Cedric


    This paper describes a local active noise control system that virtually increases the sound isolation of a dividing wall by means of a secondary source array. With the proposed method, sound pressure on the source side of the partition is reduced using an array of loudspeakers that generates destructive interference on the wall surface, where an array of error microphones is placed. The reduction of sound pressure on the incident side of the wall is expected to decrease the sound radiated into the contiguous room. The method efficiency was experimentally verified by checking the insertion loss of the active noise control system; in order to investigate the possibility of using a large number of actuators, a decentralized FXLMS control algorithm was used. Active control performances and stability were tested with different array configurations, loudspeaker directivities and enclosure characteristics (sound source position and absorption coefficient). The influence of all these parameters was investigated with the factorial design of experiments. The main outcome of the experimental campaign was that the insertion loss produced by the secondary source array, in the 50-300 Hz frequency range, was close to 10 dB. In addition, the analysis of variance showed that the active noise control performance can be optimized with a proper choice of the directional characteristics of the secondary source and the distance between loudspeakers and error microphones.

  8. Numerical Comparison of Active Acoustic and Structural Noise Control in a Stiffened Double Wall Cylinder

    Grosveld, Ferdinand W.


    The active acoustic and structural noise control characteristics of a double wall cylinder with and without ring stiffeners were numerically evaluated. An exterior monopole was assumed to acoustically excite the outside of the double wall cylinder at an acoustic cavity resonance frequency. Structural modal vibration properties of the inner and outer shells were analyzed by post-processing the results from a finite element analysis. A boundary element approach was used to calculate the acoustic cavity response and the coupled structural-acoustic interaction. In the frequency region of interest, below 500 Hz, all structural resonant modes were found to be acoustically slow and the nonresonant modal response to be dominant. Active sound transmission control was achieved by control forces applied to the inner or outer shell, or acoustic control monopoles placed just outside the inner or outer shell. A least mean square technique was used to minimize the interior sound pressures at the nodes of a data recovery mesh. Results showed that single acoustic control monopoles placed just outside the inner or outer shells resulted in better sound transmission control than six distributed point forces applied to either one of the shells. Adding stiffeners to the double wall structure constrained the modal vibrations of the shells, making the double wall stiffer with associated higher modal frequencies. Active noise control obtained for the stiffened double wall configurations was less than for the unstiffened cylinder. In all cases, the acoustic control monopoles controlled the sound transmission into the interior better than the structural control forces.

  9. Active Control of Fan Noise: Feasibility Study. Volume 6; Theoretical Analysis for Coupling of Active Noise Control Actuator Ring Sources to an Annular Duct with Flow

    Kraft, R. E.


    The objective of this effort is to develop an analytical model for the coupling of active noise control (ANC) piston-type actuators that are mounted flush to the inner and outer walls of an annular duct to the modes in the duct generated by the actuator motion. The analysis will be used to couple the ANC actuators to the modal analysis propagation computer program for the annular duct, to predict the effects of active suppression of fan-generated engine noise sources. This combined program will then be available to assist in the design or evaluation of ANC systems in fan engine annular exhaust ducts. An analysis has been developed to predict the modes generated in an annular duct due to the coupling of flush-mounted ring actuators on the inner and outer walls of the duct. The analysis has been combined with a previous analysis for the coupling of modes to a cylindrical duct in a FORTRAN computer program to perform the computations. The method includes the effects of uniform mean flow in the duct. The program can be used for design or evaluation purposes for active noise control hardware for turbofan engines. Predictions for some sample cases modeled after the geometry of the NASA Lewis ANC Fan indicate very efficient coupling in both the inlet and exhaust ducts for the m = 6 spinning mode at frequencies where only a single radial mode is cut-on. Radial mode content in higher order cut-off modes at the source plane and the required actuator displacement amplitude to achieve 110 dB SPL levels in the desired mode were predicted. Equivalent cases with and without flow were examined for the cylindrical and annular geometry, and little difference was found for a duct flow Mach number of 0.1. The actuator ring coupling program will be adapted as a subroutine to the cylindrical duct modal analysis and the exhaust duct modal analysis. This will allow the fan source to be defined in terms of characteristic modes at the fan source plane and predict the propagation to the

  10. Active Vibration Control for Helicopter Interior Noise Reduction Using Power Minimization

    Mendoza, J.; Chevva, K.; Sun, F.; Blanc, A.; Kim, S. B.


    This report describes work performed by United Technologies Research Center (UTRC) for NASA Langley Research Center (LaRC) under Contract NNL11AA06C. The objective of this program is to develop technology to reduce helicopter interior noise resulting from multiple gear meshing frequencies. A novel active vibration control approach called Minimum Actuation Power (MAP) is developed. MAP is an optimal control strategy that minimizes the total input power into a structure by monitoring and varying the input power of controlling sources. MAP control was implemented without explicit knowledge of the phasing and magnitude of the excitation sources by driving the real part of the input power from the controlling sources to zero. It is shown that this occurs when the total mechanical input power from the excitation and controlling sources is a minimum. MAP theory is developed for multiple excitation sources with arbitrary relative phasing for single or multiple discrete frequencies and controlled by a single or multiple controlling sources. Simulations and experimental results demonstrate the feasibility of MAP for structural vibration reduction of a realistic rotorcraft interior structure. MAP control resulted in significant average global vibration reduction of a single frequency and multiple frequency excitations with one controlling actuator. Simulations also demonstrate the potential effectiveness of the observed vibration reductions on interior radiated noise.

  11. An active structural acoustic control approach for the reduction of the structure-borne road noise

    Douville, Hugo; Berry, Alain; Masson, Patrice


    The reduction of the structure-borne road noise generated inside the cabin of an automobile is investigated using an Active Structural Acoustic Control (ASAC) approach. First, a laboratory test bench consisting of a wheel/suspension/lower suspension A-arm assembly has been developed in order to identify the vibroacoustic transfer paths (up to 250 Hz) for realistic road noise excitation of the wheel. Frequency Response Function (FRF) measurements between the excitation/control actuators and each suspension/chassis linkage are used to characterize the different transfer paths that transmit energy through the chassis of the car. Second, a FE/BE model (Finite/Boundary Elements) was developed to simulate the acoustic field of an automobile cab interior. This model is used to predict the acoustic field inside the cabin as a response to the measured forces applied on the suspension/chassis linkages. Finally, an experimental implementation of ASAC is presented. The control approach relies on the use of inertial actuators to modify the vibration behavior of the suspension and the automotive chassis such that its noise radiation efficiency is decreased. The implemented algorithm consists of a MIMO (Multiple-Input-Multiple-Output) feedforward configuration with a filtered-X LMS algorithm using an advanced reference signal (width FIR filters) using the Simulink/Dspace environment for control prototyping.

  12. Active control of multi-modal propagation of tonal noise in

    Laugesen, Søren


    The active control of tonal noise propagating in ducts at frequencies where many modes are able to propagate is considered. The final objective of the work reported is to cancel the prominent 450-500 Hz blade passing frequency of the rotary suction fans found in chimney stacks of power stations...... laboratory. The study of the full control system, which comprises thirty secondary sources and thirty-two error sensors, has revealed a number of new results, in particular with respect to the positioning of the sources and sensors along the length of the duct. Eventually, a reduction of the radiated power...

  13. Active3 noise reduction

    Noise reduction is a problem being encountered in a variety of applications, such as environmental noise cancellation, signal recovery and separation. Passive noise reduction is done with the help of absorbers. Active noise reduction includes the transmission of phase inverted signals for the cancellation. This paper is about a threefold active approach to noise reduction. It includes the separation of a combined source, which consists of both a noise and a signal part. With the help of interaction with the source by scanning it and recording its response, modeling as a nonlinear dynamical system is achieved. The analysis includes phase space analysis and global radial basis functions as tools for the prediction used in a subsequent cancellation procedure. Examples are given which include noise reduction of speech. copyright 1996 American Institute of Physics

  14. Novel Algorithm for Active Noise Control Systems Based on Frequency Selective Filters

    Hong-liang ZHAO


    A novel algorithm for active noise control systems based on frequency selective filters (FSFANC)is presented in the paper.The FSFANC aims at the m lti-tonal noise attenuation problem.One FSFANC system copes with one of the tonal components,and several FSFANC systems can nun independently in parallel to cancel the selected multiple tones.The proposed algorithm adopts a simple structrue with only two coefficients that can be explained as the real and imaginary parts of the structure to modelthesecondary path,and estimates the secondary path by injecting sinusoidal identification signals.Theoretical analysis and laboratory experiments show that the proposed algorithm possesses some advantages,such as simpler stricture,less computational burden,greater stability,and fast canverging speed.

  15. Active Structural Acoustic Control of Interior Noise on a Raytheon 1900D

    Palumbo, Dan; Cabell, Ran; Sullivan, Brenda; Cline, John


    An active structural acoustic control system has been demonstrated on a Raytheon Aircraft Company 1900D turboprop airliner. Both single frequency and multi-frequency control of the blade passage frequency and its harmonics was accomplished. The control algorithm was a variant of the popular filtered-x LMS implemented in the principal component domain. The control system consisted of 21 inertial actuators and 32 microphones. The actuators were mounted to the aircraft's ring frames. The microphones were distributed uniformly throughout the interior at head height, both seated and standing. Actuator locations were selected using a combinatorial search optimization algorithm. The control system achieved a 14 dB noise reduction of the blade passage frequency during single frequency tests. Multi-frequency control of the first 1st, 2nd and 3rd harmonics resulted in 10.2 dB, 3.3 dB and 1.6 dB noise reductions respectively. These results fall short of the predictions which were produced by the optimization algorithm (13.5 dB, 8.6 dB and 6.3 dB). The optimization was based on actuator transfer functions taken on the ground and it is postulated that cabin pressurization at flight altitude was a factor in this discrepancy.

  16. Characterization of electro-acoustics impedance and its application to active noise control

    HOU Hong; YANG Jianhua


    Characteristics of radiation impedance and its inducing variation of electrical impedance for a controllable source have been investigated. An impedance-based error criterion has been proposed and its application to Active Noise Control is demonstrated through a coil driven loudspeaker. A general formula of radiation impedance is derived for two control strategies, according to the criterion of total acoustic power output. The radiation impedances of some commonly used sound sources are calculated. We discuss in detail the relation between variation of the input electrical impedance and radiation impedance for the two control strategies. The measured data of the input electrical impedance from a loudspeaker agree fairly well with theoretical analysis. An AC- bridge circuit is designed in order to measure the weak variation of electrical impedance resulted from radiation impedance. The bridge relative output is unique for a certain control strategy, from which an impedance-based error criterion is then proposed and the implementation of its application to an active control system is analyzed.Numerical results of such criterion are presented. An analogue control system is set up and experiments are carried out in a semi-anechoic chamber to verify the new control approach.

  17. Structural Acoustic Characteristics of Aircraft and Active Control of Interior Noise

    Fuller, C. R.


    The reduction of aircraft cabin sound levels to acceptable values still remains a topic of much research. The use of conventional passive approaches has been extensively studied and implemented. However performance limits of these techniques have been reached. In this project, new techniques for understanding the structural acoustic behavior of aircraft fuselages and the use of this knowledge in developing advanced new control approaches are investigated. A central feature of the project is the Aircraft Fuselage Test Facility at Va Tech which is based around a full scale Cessna Citation III fuselage. The work is divided into two main parts; the first part investigates the use of an inverse technique for identifying dominant fuselage vibrations. The second part studies the development and implementation of active and active-passive techniques for controlling aircraft interior noise.

  18. Filtered-X Affine Projection Algorithms for Active Noise Control Using Volterra Filters

    Sicuranza Giovanni L


    Full Text Available We consider the use of adaptive Volterra filters, implemented in the form of multichannel filter banks, as nonlinear active noise controllers. In particular, we discuss the derivation of filtered-X affine projection algorithms for homogeneous quadratic filters. According to the multichannel approach, it is then easy to pass from these algorithms to those of a generic Volterra filter. It is shown in the paper that the AP technique offers better convergence and tracking capabilities than the classical LMS and NLMS algorithms usually applied in nonlinear active noise controllers, with a limited complexity increase. This paper extends in two ways the content of a previous contribution published in Proc. IEEE-EURASIP Workshop on Nonlinear Signal and Image Processing (NSIP '03, Grado, Italy, June 2003. First of all, a general adaptation algorithm valid for any order of affine projections is presented. Secondly, a more complete set of experiments is reported. In particular, the effects of using multichannel filter banks with a reduced number of channels are investigated and relevant results are shown.

  19. Active vibration control on a quarter-car for cancellation of road noise disturbance

    Belgacem, Walid; Berry, Alain; Masson, Patrice


    In this paper, a methodology is presented for the cancellation of road noise, from the analysis of vibration transmission paths for an automotive suspension to the design of an active control system using inertial actuators on a suspension to reduce the vibrations transmitted to the chassis. First, experiments were conducted on a Chevrolet Epica LS automobile on a concrete test track to measure accelerations induced on the suspension by the road. These measurements were combined with experimental Frequency Response Functions (FRFs) measured on a quarter-car test bench to reconstruct an equivalent three dimensional force applied on the wheel hub. Second, FRFs measured on the test bench between the three-dimensional driving force and forces at each suspension/chassis linkage were used to characterize the different transmission paths of vibration energy to the chassis. Third, an experimental model of the suspension was constructed to simulate the configuration of the active control system, using the primary (disturbance) FRFs and secondary (control) FRFs also measured on the test bench. This model was used to optimize the configuration of the control actuators and to evaluate the required forces. Finally, a prototype of an active suspension was implemented and measurements were performed in order to assess the performance of the control approach. A 4.6 dB attenuation on transmitted forces was obtained in the 50-250 Hz range.

  20. Active control of counter-rotating open rotor interior noise in a Dornier 728 experimental aircraft

    Haase, Thomas; Unruh, Oliver; Algermissen, Stephan; Pohl, Martin


    The fuel consumption of future civil aircraft needs to be reduced because of the CO2 restrictions declared by the European Union. A consequent lightweight design and a new engine concept called counter-rotating open rotor are seen as key technologies in the attempt to reach this ambitious goals. Bearing in mind that counter-rotating open rotor engines emit very high sound pressures at low frequencies and that lightweight structures have a poor transmission loss in the lower frequency range, these key technologies raise new questions in regard to acoustic passenger comfort. One of the promising solutions for the reduction of sound pressure levels inside the aircraft cabin are active sound and vibration systems. So far, active concepts have rarely been investigated for a counter-rotating open rotor pressure excitation on complex airframe structures. Hence, the state of the art is augmented by the preliminary study presented in this paper. The study shows how an active vibration control system can influence the sound transmission of counter-rotating open rotor noise through a complex airframe structure into the cabin. Furthermore, open questions on the way towards the realisation of an active control system are addressed. In this phase, an active feedforward control system is investigated in a fully equipped Dornier 728 experimental prototype aircraft. In particular, the sound transmission through the airframe, the coupling of classical actuators (inertial and piezoelectric patch actuators) into the structure and the performance of the active vibration control system with different error sensors are investigated. It can be shown that the active control system achieves a reduction up to 5 dB at several counter-rotating open rotor frequencies but also that a better performance could be achieved through further optimisations.

  1. A study of the performance of an Olson type active noise controller and the possibility of the reduction of cabin noise

    Keith, S. E.; Scholaert, H. S. B.


    Designed to reduce sound levels by means of an electronic transducing system, the active noise controller is a basic feedback control system composed of a speaker, microphone, amplifier and control unit. Because the scheme can be effective in reducing low frequency noise, it is of particular interest to aircraft manufacturers since attenuation of low frequency noise to increase passenger comfort can be at once costly and cumbersome when conventional sound absorption methods are employed. Olson and May's pioneering work in the 1950's in developing an electronic sound absorber which appeared to be successful over small volumes in a unidirectional sound field is re-examined as well as more recent developments in an effort to test their suitability to the aircraft industry. The results suggest only limited possible use for all systems studied.

  2. Chain reconfiguration in active noise

    Samanta, Nairhita; Chakrabarti, Rajarshi


    In a typical single molecule experiment, the dynamics of an unfolded protein is studied by determining the reconfiguration time using long-range Förster resonance energy transfer, where the reconfiguration time is the characteristic decay time of the position correlation between two residues of the protein. In this paper we theoretically calculate the reconfiguration time for a single flexible polymer in the presence of active noise. The study suggests that though the mean square displacement grows faster, the chain reconfiguration is always slower in the presence of long-lived active noise with exponential temporal correlation. Similar behavior is observed for a worm-like semi-flexible chain and a Zimm chain. However it is primarily the characteristic correlation time of the active noise and not the strength that controls the increase in the reconfiguration time. In brief, such active noise makes the polymer move faster but the correlation loss between the monomers becomes slow.

  3. Chain reconfiguration in active noise

    In a typical single molecule experiment, the dynamics of an unfolded protein is studied by determining the reconfiguration time using long-range Förster resonance energy transfer, where the reconfiguration time is the characteristic decay time of the position correlation between two residues of the protein. In this paper we theoretically calculate the reconfiguration time for a single flexible polymer in the presence of active noise. The study suggests that though the mean square displacement grows faster, the chain reconfiguration is always slower in the presence of long-lived active noise with exponential temporal correlation. Similar behavior is observed for a worm-like semi-flexible chain and a Zimm chain. However it is primarily the characteristic correlation time of the active noise and not the strength that controls the increase in the reconfiguration time. In brief, such active noise makes the polymer move faster but the correlation loss between the monomers becomes slow. (paper)

  4. Active road noise reduction

    Vraničar, Primož


    Theoretical principle of noise cancellation can be realized in the ideal studio conditions, but when the experiment is put into actual space and realized, we can see that the sound only partly cancels itself, on some frequencies more and on some less. However, in construction engineering we are not only dealing with certain frequencies but with frequency spectrums, if not with the whole frequency field. It is relatively hard to control the noise in traffic. We are dealing with a larger freque...

  5. Development of adaptive IIR filtered-e LMS algorithm for active noise control

    SUN Xu; MENG Guang; TENG Pengxiao; CHEN Duanshi


    Compared to finite impulse response (FIR) filters, infinite impulse response (IIR)filters can match the system better with much fewer coefficients, and hence the computationload is saved and the performance improves. Therefore, it is attractive to use IIR filters insteadof FIR filters in active noise control (ANC). However, filtered-U LMS (FULMS) algorithm, theIIR filter-based algorithm commonly used so far cannot ensure global convergence. A new IIRfilter based adaptive algorithm, which can ensure global convergence with computation loadonly slightly increasing, is proposed in this paper. The new algorithm is called as filtered-eLMS algorithm since the error signal of which need to be filtered. Simulation results show thatthe FELMS algorithm presents better performance than the FULMS algorithm.

  6. Simultaneous BVI noise and vibration reduction in rotorcraft using actively-controlled flaps and including performance considerations

    Patt, Daniel A.

    This work presents the development and application of an active control approach for reduction of both vibration and noise induced by helicopter rotor blade vortex interaction (BVI). Control is implemented through single or dual actively controlled flaps (ACFs) on each blade. Low-speed helicopter flight is prone to severe BVI, resulting in elevated vibration and noise levels. Existing research has suggested that when some form of active control is used to reduce vibration, noise will increase and vice versa. The present research achieves simultaneous reduction of noise and vibration, and also investigates the physical sources of the observed reduction. The initial portion of this work focused on developing a tool for simulating helicopter noise and vibrations in the BVI flight regime. A method for predicting compressible unsteady blade surface pressure distribution on rotor blades was developed and combined with an enhanced free-wake model and an acoustic prediction tool with provisions for blade flexibility. These elements were incorporated within an aeroelastic analysis featuring fully coupled flap-lag-torsional blade dynamics. Subsequently, control algorithms were developed that were effective for reducing noise and vibration even in the nonlinear BVI flight regime; saturation limits were incorporated constraining flap deflections to specified limits. The resulting simulation was also validated with a wide range of experimental data, achieving excellent correlation. Finally, a number of active control studies were performed. Multi-component vibration reductions of 40--80% could be achieved, while incurring a small noise penalty. Noise was reduced using an onboard feedback microphone; reductions of 4--10 dB on the advancing side were observed on a plane beneath the rotor when using dual flaps. Finally, simultaneous noise and vibration reduction was studied. A reduction of about 5 dB in noise on the advancing side combined with a 60% reduction in vibration was

  7. Noise control mechanisms of inside aircraft

    Zverev, A. Ya.


    World trends in the development of methods and approaches to noise reduction in aircraft cabins are reviewed. The paper discusses the mechanisms of passive and active noise and vibration control, application of "smart" and innovative materials, new approaches to creating all fuselage-design elements, and other promising directions of noise control inside aircraft.

  8. A Control Source Structure of Single Loudspeaker and Rear Sound Interference for Inexpensive Active Noise Control

    Yasuhide Kobayashi


    phase-lag is imposed by the Swinbanks' source and the rear sound interference. Thirdly, effects on control performances of control source structures are examined by control experiments with robust controllers.

  9. Low noise control valve

    Noise is one of the problems associated with the use of any type of control valve in systems involving the flow of fluids. The advent of OSHA standards has prompted control valve manufacturers to design valves with special trim to lower the sound pressure level to meet these standards. However, these levels are in some cases too high, particularly when a valve must be located in or near an area where people are working at tasks requiring a high degree of concentration. Such locations are found around and near research devices and in laboratory-office areas. This paper describes a type of fluid control device presently being used at PPL as a bypass control valve in deionized water systems and designed to reduce sound pressure levels considerably below OSHA standards. Details of the design and construction of this constant pressure drop variable flow control valve are contained in the text and are shown in photographs and drawings. Test data taken are included

  10. The use of active vibration control for the reduction of ICE interior noise

    Schirmacher, R. [Mueller-BBM GmbH - Beratende Ingenieure fuer Akustik, Planegg (Germany)


    First generation ICE high speed trains show a disturbing low frequency noise of about 100 Hz audible inside the coaches. It is excited by unround wheels, propagates via the bogie to the body of the coach and is finally radiated as airborne sound. A mixed concept of active suspension at the bogie in connection with adaptive residual noise minimisation inside the passenger compartment is successfully applied to the problem. A prototype system utilizing piezo ceramic actuators was installed and tested on the rolling rig of Deutsche Bahn in Munich. The noise level reductions at single harmonics were more than 12 dB averaged over the whole compartment and more than 20 dB at single seats. Measurement results and practical experiences with the system are reported. (orig.)

  11. Control strategies for aircraft airframe noise reduction

    Li Yong; Wang Xunnian; Zhang Dejiu


    With the development of low-noise aircraft engine,airframe noise now represents a major noise source during the commercial aircraft's approach to landing phase.Noise control efforts have therefore been extensively focused on the airframe noise problems in order to further reduce aircraft overall noise.In this review,various control methods explored in the last decades for noise reduction on airframe components including high-lift devices and landing gears are summarized.We introduce recent major achievements in airframe noise reduction with passive control methods such as fairings,deceleration plates,splitter plates,acoustic liners,slat cove cover and side-edge replacements,and then discuss the potential and control mechanism of some promising active flow control strategies for airframe noise reduction,such as plasma technique and air blowing/suction devices.Based on the knowledge gained throughout the extensively noise control testing,a few design concepts on the landing gear,high-lift devices and whole aircraft are provided for advanced aircraft low-noise design.Finally,discussions and suggestions are given for future research on airframe noise reduction.

  12. Adjusting phenotypes by noise control.

    Kyung H Kim


    Full Text Available Genetically identical cells can show phenotypic variability. This is often caused by stochastic events that originate from randomness in biochemical processes involving in gene expression and other extrinsic cellular processes. From an engineering perspective, there have been efforts focused on theory and experiments to control noise levels by perturbing and replacing gene network components. However, systematic methods for noise control are lacking mainly due to the intractable mathematical structure of noise propagation through reaction networks. Here, we provide a numerical analysis method by quantifying the parametric sensitivity of noise characteristics at the level of the linear noise approximation. Our analysis is readily applicable to various types of noise control and to different types of system; for example, we can orthogonally control the mean and noise levels and can control system dynamics such as noisy oscillations. As an illustration we applied our method to HIV and yeast gene expression systems and metabolic networks. The oscillatory signal control was applied to p53 oscillations from DNA damage. Furthermore, we showed that the efficiency of orthogonal control can be enhanced by applying extrinsic noise and feedback. Our noise control analysis can be applied to any stochastic model belonging to continuous time Markovian systems such as biological and chemical reaction systems, and even computer and social networks. We anticipate the proposed analysis to be a useful tool for designing and controlling synthetic gene networks.

  13. A multi-resolution filtered-x LMS algorithm based on discrete wavelet transform for active noise control

    Qiu, Z.; Lee, C.-M.; Xu, Z. H.; Sui, L. N.


    We have developed a new active control algorithm based on discrete wavelet transform (DWT) for both stationary and non-stationary noise control. First, the Mallat pyramidal algorithm is introduced to implement the DWT, which can decompose the reference signal into several sub-bands with multi-resolution and provides a perfect reconstruction (PR) procedure. To reduce the extra computational complexity introduced by DWT, an efficient strategy is proposed that updates the adaptive filter coefficients in the frequency domainDeepthi B.B using a fast Fourier transform (FFT). Based on the reference noise source, a 'Haar' wavelet is employed and by decomposing the noise signal into two sub-band (3-band), the proposed DWT-FFT-based FXLMS (DWT-FFT-FXLMS) algorithm has greatly reduced complexity and a better convergence performance compared to a time domain filtered-x least mean square (TD-FXLMS) algorithm. As a result of the outstanding time-frequency characteristics of wavelet analysis, the proposed DWT-FFT-FXLMS algorithm can effectively cancel both stationary and non-stationary noise, whereas the frequency domain FXLMS (FD-FXLMS) algorithm cannot approach this point.

  14. Development of Adjustable Absorption Acoustic Liner for Active Fan Noise Control

    小林, 紘; Kobayashi, Hiroshi


    Due to strong demands from communities adjacent to airports for the suppression aircraft noise, a new aircraft noise certification standard as set out in ICAO Chapter 4 was formulated and will come into effect in 2006 for new subsonic aircrafts. Currently, not only aircraft noise affecting communities surrounding airports but also aircraft noise at night, during climb and while cruising have become serious issues. In order to solve these issues, at NAL, new techniques and systems have been de...

  15. Adaptive Volterra filter with continuous lp-norm using a logarithmic cost for nonlinear active noise control

    Lu, Lu; Zhao, Haiquan


    The filtered-x least mean lp-norm (FxLMP) algorithm is proven to be useful for nonlinear active noise control (NANC) systems. However, its performance deteriorates when the impulsive noises are presented in NANC systems. To surmount this shortcoming, a new nonlinear adaptive algorithm based on Volterra expansion model (VFxlogLMP) is developed in this paper, which is derived by minimizing the lp-norm of logarithmic cost. It is found that the FxLMP and VFxlogLMP require to select an appropriate value of p according to the prior information on noise characteristics, which prohibit their practical applications. Based on VFxlogLMP algorithm, we proposed a continuous lp-norm algorithm with logarithmic cost (VFxlogCLMP), which does not need the parameter selection and thresholds estimation. Benefiting from the various error norms for 1≤p≤2, it remains the robustness of VFxlogLMP. Moreover, the convergence behavior of VFxlogCLMP for moving average secondary paths and stochastic input signals is performed. Compared to the existing algorithms, two versions of the proposed algorithms have much better convergence and stability in impulsive noise environments.

  16. Escape conditioning and low-frequency whole-body vibration - The effects of frequency, amplitude, and controls for noise and activation.

    Wike, E. L.; Wike, S. S.


    Seven experiments are reported on low-frequency whole-body vibration and rats' escape conditioning in a modified Skinner box. In the first three studies, conditioning was observed but was independent of frequency. In experiment four, the number of escape responses was directly related to vibration amplitude. Experiment five was a control for vibration noise and noise termination; experiments six and seven studied vibration-induced activation. Noise termination did not produce conditioning. In experiment six, subjects made more responses when responding led to termination than when it did not. In experiment seven, subjects preferred a bar which terminated vibration to one which did not.

  17. Increased noise level of purkinje cell activities minimizes impact of their modulation during sensorimotor control.

    Hoebeek, F.E.; Stahl, J.S.; Alphen, A.M. van; Schonewille, M.; Luo, C.; Rutteman, M.; Maagdenberg, A.M.J.M. van den; Molenaar, P.C.; Goossens, H.H.L.M.; Frens, M.A.; Zeeuw, C.I. de


    While firing rate is well established as a relevant parameter for encoding information exchanged between neurons, the significance of other parameters is more conjectural. Here, we show that regularity of neuronal spike activities affects sensorimotor processing in tottering mutants, which suffer fr

  18. Noise in the Library: Effects and Control.

    Eagan, Ann


    Describes the physiological and psychological effects of noise in libraries and suggests methods of controlling noise from telephones, computers, printers, and photocopiers. Hearing loss and stress-related problems are discussed, the effects of noise on performance are described, and planning is emphasized as a method of avoiding noise problems.…

  19. Noise Control in Space Shuttle Orbiter

    Goodman, Jerry R.


    Acoustic limits in habitable space enclosures are required to ensure crew safety, comfort, and habitability. Noise control is implemented to ensure compliance with the acoustic requirements. The purpose of this paper is to describe problems with establishing acoustic requirements and noise control efforts, and present examples of noise control treatments and design applications used in the Space Shuttle Orbiter. Included is the need to implement the design discipline of acoustics early in the design process, and noise control throughout a program to ensure that limits are met. The use of dedicated personnel to provide expertise and oversight of acoustic requirements and noise control implementation has shown to be of value in the Space Shuttle Orbiter program. It is concluded that to achieve acceptable and safe noise levels in the crew habitable space, early resolution of acoustic requirements and implementation of effective noise control efforts are needed. Management support of established acoustic requirements and noise control efforts is essential.

  20. Controlled exposure to diesel exhaust and traffic noise - Effects on oxidative stress and activation in mononuclear blood cells

    Hemmingsen, Jette Gjerke; Møller, Peter; Jantzen, Kim;


    Particulate air pollution increases risk of cancer and cardiopulmonary disease, partly through oxidative stress. Traffic-related noise increases risk of cardiovascular disease and may cause oxidative stress. In this controlled random sequence study, 18 healthy subjects were exposed for 3h to diesel...... exhaust (DE) at 276μg/m(3) from a passenger car or filtered air, with co-exposure to traffic noise at 48 or 75dB(A). Gene expression markers of inflammation, (interleukin-8 and tumor necrosis factor), oxidative stress (heme oxygenase (decycling-1)) and DNA repair (8-oxoguanine DNA glycosylase (OGG1)) were...... unaltered in peripheral blood mononuclear cells (PBMCs). No significant differences in DNA damage levels, measured by the comet assay, were observed after DE exposure, whereas exposure to high noise levels was associated with significantly increased levels of hOGG1-sensitive sites in PBMCs. Urinary levels...

  1. Fuselage panel noise attenuation by piezoelectric switching control

    This paper describes a problem that we encountered in our noise attenuation project and our solution for it. We intend to attenuate low-frequency noise that transmits through aircraft fuselage panels. Our method of noise attenuation is implemented with a piezoelectric semi-active system having a selective switch instead of an active energy-supply system. The semi-active controller is based on the predicted sound pressure distribution obtained from acoustic emission analysis. Experiments and numerical simulations demonstrate that the semi-active method attenuates acoustic levels of not only the simple monochromatic noise but also of broadband noise. We reveal that tuning the electrical parameters in the circuit is the key to effective noise attenuation, to overcome the acoustic excitation problem due to sharp switching actions, as well as to control chattering problems. The results obtained from this investigation provide meaningful insights into designing noise attenuation systems for comfortable aircraft cabin environments

  2. Fuselage panel noise attenuation by piezoelectric switching control

    Makihara, Kanjuro; Miyakawa, Takeya; Onoda, Junjiro; Minesugi, Kenji


    This paper describes a problem that we encountered in our noise attenuation project and our solution for it. We intend to attenuate low-frequency noise that transmits through aircraft fuselage panels. Our method of noise attenuation is implemented with a piezoelectric semi-active system having a selective switch instead of an active energy-supply system. The semi-active controller is based on the predicted sound pressure distribution obtained from acoustic emission analysis. Experiments and numerical simulations demonstrate that the semi-active method attenuates acoustic levels of not only the simple monochromatic noise but also of broadband noise. We reveal that tuning the electrical parameters in the circuit is the key to effective noise attenuation, to overcome the acoustic excitation problem due to sharp switching actions, as well as to control chattering problems. The results obtained from this investigation provide meaningful insights into designing noise attenuation systems for comfortable aircraft cabin environments.

  3. Estimation and global control of noise reflections

    Friot, Emmanuel


    In theory, active control could be used to reduce the unwanted noise reflections from surfaces such as a submarine hull or the walls of an anechoic room. In the recent years, a real-time algorithm has been developed to this effect at the Laboratoire de M\\'ecanique et d'Acoustique: the noise scattered by the surface is estimated through linear filtering of acoustic pressure signals provided by ordinary microphones and an adaptive feedforward algorithm minimizes the resulting error signals. The paper summarizes the theory underlying the control algorithm, which stems from the integral representation of the scattered pressure, and presents the successive experiments which have been conducted with it: control of terminal reflections in a duct, control of the noise scattered by a parallelepiped in an anechoic room, estimation of the noise reflections on the walls of a small room. It appears that an accurate identification of the linear filters that account for the surface scattering leads to an effective estimatio...

  4. Noise and Vibration Control of Combustion Engine Vehicles

    Winberg, Mathias


    Noise and vibrations have over the last two decades been regarded as significant environmental health problems. Regulations regarding acoustic as well as vibration levels have therefore become more stringent. This thesis embraces two different techniques to reduce unwanted noise and vibrations, spectral subtraction and active noise and vibration control. The applications treated for noise and vibration problems are mainly means of transportation driven by combustion engines as for example, he...

  5. Genetic noise control via protein oligomerization

    Ghim, C; Almaas, E


    Gene expression in a cell entails random reaction events occurring over disparate time scales. Thus, molecular noise that often results in phenotypic and population-dynamic consequences sets a fundamental limit to biochemical signaling. While there have been numerous studies correlating the architecture of cellular reaction networks with noise tolerance, only a limited effort has been made to understand the dynamical role of protein-protein associations. We have developed a fully stochastic model for the positive feedback control of a single gene, as well as a pair of genes (toggle switch), integrating quantitative results from previous in vivo and in vitro studies. In particular, we explicitly account for the fast protein binding-unbinding kinetics, RNA polymerases, and the promoter/operator sequences of DNA. We find that the overall noise-level is reduced and the frequency content of the noise is dramatically shifted to the physiologically irrelevant high-frequency regime in the presence of protein dimerization. This is independent of the choice of monomer or dimer as transcription factor and persists throughout the multiple model topologies considered. For the toggle switch, we additionally find that the presence of a protein dimer, either homodimer or heterodimer, may significantly reduce its intrinsic switching rate. Hence, the dimer promotes the robust function of bistable switches by preventing the uninduced (induced) state from randomly being induced (uninduced). The specific binding between regulatory proteins provides a buffer that may prevent the propagation of fluctuations in genetic activity. The capacity of the buffer is a non-monotonic function of association-dissociation rates. Since the protein oligomerization per se does not require extra protein components to be expressed, it provides a basis for the rapid control of intrinsic or extrinsic noise. The stabilization of phenotypically important toggle switches, and nested positive feedback loops in

  6. Condominium Design: Good and Bad Noise Control.

    Hargens, C. W.; Schutz, Victor K.

    This paper discusses pitfalls in condominium design and the incorpoation of related noise control problems into classroom situations. Two case studies are provided, and a list of architectural noise problems found in many condominiums is included. (CP)

  7. Holistic control of ship noise emissions

    Borelli Davide; Gaggero Tomaso; Rizzuto Enrico; Schenone Corrado


    The sustainability of anthropogenic activities at sea is recently gaining more and more attention. As regards shipping, emissions from ships into the environment of various nature (engine exhaust gases, anti-fouling paints leaching, ballast exchange, releases at sea of oil and other noxious liquid or solid cargoes, of sewage and of garbage) have been recognized as sources of pollution and therefore controlled and limited since a long time. The subject of noise emission...

  8. Feedback Control for Noise Reduction Program

    Tucker, Jerry H.


    As part of Langley Research Center's continuing noise reduction program, an active noise control system (ANC) is being developed to suppress noise inside an aircraft cabin. This interior noise reduction system consists of the following major components: 1. Several accelerometers. 2. An input amplifier. 3. A digital signal processor (DSP) system that includes an analog to digital converter (ADC) and a digital to analog converter (DAC). 4. A high voltage power amplifier. 5. PZT actuators. 6. Power supply and distribution. The accelerometers detect interior panel vibrations. The accelerometer signals are fed to the input amplifier where they are conditioned prior to being sent to the ADC. The DSP receives the digitized signals form the ADC, processes these signals, and sends the result to the DAC. The DAC's analog output is used as input to the high voltage power amplifier. The power amplifier drives the PZT actuators to cancel noise form 50 to 1,300 Hz. The specific area of concern for this work was development of a DSP system that could be used for an actual flight demonstration. It was decided to base the system on a commercially available DSP board, the Spectrum Digital eZdsp. This was complicated by the fact that the ADC and DAC capabilities available on the eZdsp board were not sufficient to meet the system specification. Designing and fabricating a special ADC and DAC daughter card for the eZdsp circumvented this problem. The DSP system hardware has been successfully tested and is currently being integrated into the complete noise reduction system. This work has been completed in collaboration with another ASEE Fellow, Dr.William Edmonson from Hampton University and was conducted under the direction of the principle investigator, Dr. Qamar A. Shams of the Instrumentation Systems Development Branch, as part of a continuing noise reduction program.

  9. Universal control induced by noise

    Arenz, Christian; Burgarth, Daniel; Facchi, Paolo; Giovannetti, Vittorio; Nakazato, Hiromichi; Pascazio, Saverio; Yuasa, Kazuya


    On the basis of the quantum Zeno effect, it has been recently shown [D. K. Burgarth et al., Nat. Commun. 5, 5173 (2014), 10.1038/ncomms6173] that a strong-amplitude-damping process applied locally on a part of a quantum system can have a beneficial effect on the dynamics of the remaining part of the system. Quantum operations that cannot be implemented without the dissipation become achievable by the action of the strong dissipative process. Here we generalize this idea by identifying decoherence-free subspaces (DFSs) as the subspaces in which the dynamics becomes more complex. Applying methods from quantum control theory, we characterize the set of reachable operations within the DFSs. We provide three examples that become fully controllable within the DFSs while the control over the original Hilbert space in the absence of dissipation is trivial. In particular, we show that the (classical) Ising Hamiltonian is turned into a Heisenberg Hamiltonian by strong collective decoherence, which provides universal quantum computation within the DFSs. Moreover, we perform numerical gate optimization to study how the process fidelity scales with the noise strength. As a by-product, a subsystem fidelity that can be applied in other optimization problems for open quantum systems is developed.

  10. 单极子声源平面空间有源降噪的最短距离%The Shortest Distance of Monopole Noise Sources in Plat Space under Active Noise Control

    姚加飞; 郭爽


    以单极子噪声源与单极子抗噪声源组成的声场为研究对象,得出用单极子抗噪声源控制单极子噪声源,使两声源所在的平面空间内的总声功率最小时两声源本身的声强的关系。并计算空间内任意一点的径向平均有功声强。得出最小径向平均有功声强与声源的频率和两声源的距离有关,在一定频率下,两声源距离越近,控制后的径向平均有功声强越小,距离一定的情况下,频率越小,径向平均有功声强越小。通过仿真实验进行验证,并最终得到某些低频噪声达到全空间消声时噪声源与抗噪声源的最短距离。%This article studies the sound fields of the monopole noise source and monopole anti-noise source. The relationship between the sound intensity of the noise source and the sound intensity of the anti-noise source under the condition of the least sound power in the plat sound field is obtained. In addition, the radial average active sound intensity at any point in the sound field is calculated, which is found to be related to the frequency of the sound source and the distance between the two sources. For a fixed frequency, the radial average active sound intensity decreases with the distance between the two sources increasing after the control. For the fixed distance between the two sources, the radial average active sound intensity decreases with the frequency decreasing after the control. Through the MATLAB simulation, the shortest distance between the noise source and anti-noise source when the sound intensities of some low-frequency noises in the whole space vanish is obtained.

  11. Active Control of Fan Noise: Feasibility Study. Volume 5; Numerical Computation of Acoustic Mode Reflection Coefficients for an Unflanged Cylindrical Duct

    Kraft, R. E.


    A computational method to predict modal reflection coefficients in cylindrical ducts has been developed based on the work of Homicz, Lordi, and Rehm, which uses the Wiener-Hopf method to account for the boundary conditions at the termination of a thin cylindrical pipe. The purpose of this study is to develop a computational routine to predict the reflection coefficients of higher order acoustic modes impinging on the unflanged termination of a cylindrical duct. This effort was conducted wider Task Order 5 of the NASA Lewis LET Program, Active Noise Control of aircraft Engines: Feasibility Study, and will be used as part of the development of an integrated source noise, acoustic propagation, ANC actuator coupling, and control system algorithm simulation. The reflection coefficient prediction will be incorporated into an existing cylindrical duct modal analysis to account for the reflection of modes from the duct termination. This will provide a more accurate, rapid computation design tool for evaluating the effect of reflected waves on active noise control systems mounted in the duct, as well as providing a tool for the design of acoustic treatment in inlet ducts. As an active noise control system design tool, the method can be used preliminary to more accurate but more numerically intensive acoustic propagation models such as finite element methods. The resulting computer program has been shown to give reasonable results, some examples of which are presented. Reliable data to use for comparison is scarce, so complete checkout is difficult, and further checkout is needed over a wider range of system parameters. In future efforts the method will be adapted as a subroutine to the GEAE segmented cylindrical duct modal analysis program.

  12. Noise screen for attitude control system

    Rodden, John J. (Inventor); Stevens, Homer D. (Inventor); Hong, David P. (Inventor); Hirschberg, Philip C. (Inventor)


    An attitude control system comprising a controller and a noise screen device coupled to the controller. The controller is adapted to control an attitude of a vehicle carrying an actuator system that is adapted to pulse in metered bursts in order to generate a control torque to control the attitude of the vehicle in response to a control pulse. The noise screen device is adapted to generate a noise screen signal in response to the control pulse that is generated when an input attitude error signal exceeds a predetermined deadband attitude level. The noise screen signal comprises a decaying offset signal that when combined with the attitude error input signal results in a net attitude error input signal away from the predetermined deadband level to reduce further control pulse generation.

  13. Genetic noise control via protein oligomerization

    Almaas Eivind


    Full Text Available Abstract Background Gene expression in a cell entails random reaction events occurring over disparate time scales. Thus, molecular noise that often results in phenotypic and population-dynamic consequences sets a fundamental limit to biochemical signaling. While there have been numerous studies correlating the architecture of cellular reaction networks with noise tolerance, only a limited effort has been made to understand the dynamic role of protein-protein interactions. Results We have developed a fully stochastic model for the positive feedback control of a single gene, as well as a pair of genes (toggle switch, integrating quantitative results from previous in vivo and in vitro studies. In particular, we explicitly account for the fast binding-unbinding kinetics among proteins, RNA polymerases, and the promoter/operator sequences of DNA. We find that the overall noise-level is reduced and the frequency content of the noise is dramatically shifted to the physiologically irrelevant high-frequency regime in the presence of protein dimerization. This is independent of the choice of monomer or dimer as transcription factor and persists throughout the multiple model topologies considered. For the toggle switch, we additionally find that the presence of a protein dimer, either homodimer or heterodimer, may significantly reduce its random switching rate. Hence, the dimer promotes the robust function of bistable switches by preventing the uninduced (induced state from randomly being induced (uninduced. Conclusion The specific binding between regulatory proteins provides a buffer that may prevent the propagation of fluctuations in genetic activity. The capacity of the buffer is a non-monotonic function of association-dissociation rates. Since the protein oligomerization per se does not require extra protein components to be expressed, it provides a basis for the rapid control of intrinsic or extrinsic noise. The stabilization of regulatory circuits

  14. Traffic noise control of a city

    Long exposure to noise due to traffic affects our health and comfort. A noise level up to 45 dB is acceptable for the buildings in the city. A traffic noise study was conducted in Karachi at places of high traffic flow. The noise level was between 75-85 dB. Residential and commercial buildings had sound level up to 79 dB. Reducing vehicle noise by using proper muffler and acoustic treatment should first control traffic noise. Then noise can be reduced by 10-15 dB by constructing barriers of wood or concrete along roadside. Barrier height for sound attenuation can be found from Fresnel Number. The barrier reduces noise better if width at the top is increased and an inward bend of 60 degree is placed at the top. Where feasible a 4-5 meter high concrete barrier is recommended otherwise the nearby buildings from the road should be insulated and acoustically treated. (author)

  15. Retrofitting reciprocating compressors for noise control

    The Alberta Energy Resources Conservation Board recently enacted their noise control directive ID 88-1. The effects of this regulation on the operation of an oil and gas facility are discussed, and a specific case history is presented to provide a disciplined strategy for noise attenuation retrofits. An investigation was carried out into sound sources at a reciprocating compressor gas plant, revealing several sound sources: engine exhaust stacks, engine exhaust silencer shells, direct-drive fan cooler inlets, direct drive fan cooler outlets, aerial cooler inlets and aerial cooler outlets. Details are presented of the investigative techniques and order-ranking of sources by decibel level. When controlling engine exhaust noise, silencers or mufflers are the preferred treatment. Choice of type (reactive or absorptive) and specification of acoustical performance of a silencer are discussed. The gas plant achieved noise reductions of 6-13 dB, measured at affected residences, through the use of engine exhaust silencers. 4 figs., 2 tabs

  16. Noise control of radiological monitoring equipment

    Although vacuum pumps on continuous air monitors (CAMs) do not produce noise levels above regulatory limits, engineering controls were used to establish a safer work environment. Operations performed in areas where CAMs are located are highly specialized and require precision work when handling nuclear materials, heavy metals, and inert gases. Traditional methods for controlling noise such as enclosing or isolating the source and the use of personal protection equipment were evaluated. An innovative solution was found by retrofitting CAMs with air powered multistage ejectors pumps. By allowing the air to expand in several chambers to create a vacuum, one can eliminate the noise hazard altogether. In facilities with adequate pressurized air, use of these improved ejector pumps may be a cost-effective replacement for noisy vacuum pumps. A workplace designed or engineered with noise levels as low as possible or as close to background adds to increased concentration, attention to detail, and increased production

  17. Measurement and control of occupational noise

    High level of environmental and occupational noise remain a problem all over the world. As problems and complaints increased dramatically by the end of the 19th and beginning of the 20th centuries focusing on the problem was intensified. In this thesis occupational noise levels at different places were measured and compared with the international permissible levels using the integrating sound level meter (Quest 2800). The calibration of the instrument was carried out before and after each measurement using the acoustic calibrator (Quest CA-12B calibrator). The method which was followed was measuring the sound pressure level of the different noise sources over a broad frequency band covering the audible frequency range using the (octave band filter, model OB-100), disregrading variation with time. Since the human ear is most sensitive in the 2-5 khz range of frequencies and least sensitive at extremely high and low frequencies the instrument was adjusted on the A weighting net work which varies with frequencies in a very similar way as that of the human ear. From the obtained results, some noise levels which were recorded were within the permissible levels i.e. below 90 dba and some noise levels were higher than the permissible limit as in janzour textile factory (95 dba), The welding workshop (120 dba), Benghazi Macaroni factory (100 dba), and near the air blowers at Zletin cement factory, Benghazi cement factory (97-10-dba) in these cases suggestions were made to minimize the problem. Concerning the noise control, four methods of noise control were tested, these methods were: reducing noise by sound absorbing material at Sirt local broadcasting radio, reducing noise by keeping a distance from the noise source, at the Boilers hall at REWDC, reducing noise by enclosures, at the compressors room at Zletin cement factory, and finally reducing noise by performing regular maintenance at Garabolli photo development centre. The percentage of noise reduction was 21%, 12

  18. Residential Noise Control Requirements for Powerline Communications Channel

    Guillen, Edward; Lopez, Julian; Padilla, Daniel


    Noises on powerline communication channels such as coloured noise, narrow band noise, periodic impulsive noise and asynchronous impulsive noise affect PLC network throughput. However, these noises can be successfully controlled by band-pass and bandstop filters installed on strategic PLC network connection points. It's necessary to establish a model to probe if the noise measurements on this work can be applied on industrial environments and if the noise can affect PLC networks installed on n...

  19. A case study, noise control for a low frequency noise compliance situation

    Farquharson, James; Parent, Michel [CET FDI Acoustics Inc. (Canada)], email:, email:


    The current version of the energy resources conservation board (ERCB) Directive 038: noise control, has recently been modified to include assessment and regulation of low frequency noise. This has led to additional concerns and considerations in noise control measurement. This paper examines a specific example and introduces the low frequency noise assessment and consequent development of noise control measures. Prior to the new Directive 038 regulation, noise compliance in industrial facilities was determined by demonstrating that the sound level in residential areas was beneath a certain threshold, the permissible sound level, fixed by the ERCB. Noise mitigation measures aimed to reduce noise to a point where the overall sound level was below this threshold. With the introduction of low frequency noise considerations, industrials must take into account tonal noise in the low frequency spectrum, using A and C-weighted noise measurements, and third octave band frequency tones, resulting in a new approach for noise control development.

  20. Noise Control and Noise Evaluation in Aircraft Engines

    石井, 達哉; Ishii, Tatsuya


    Aircraft engine noise emitted for example by the jet exhaust, fan, compressor, turbine and combustor is the predominant factor in total aircraft noise during take-off and landing. As a result of enormous efforts to alleviate engine noise, noise levels have been improved by more than 20 dB compared to the first generation of airliners. However, the growing volume of air transport means that further noise reduction is still required. With this background, we decided to concentrate on two techni...

  1. Noise-control needs in the developing energy technologies

    Keast, D.N.


    The noise characteristics of existing energy conversion technologies, e.g., from obtaining and processing fossil fuels to power plants operations, and of developing energy technologies (wind, geothermal sources, solar energy or fusion systems) are discussed in terms of the effects of noise on humans, animals, structures, and equipment and methods for noise control. Regulations for noise control are described. Recommendations are made for further research on noise control and noise effects. (LCL)

  2. The Traffic Noise Index: A Method of Controlling Noise Nuisance.

    Langdon, F. J.; Scholes, W. E.

    This building research survey is an analysis of the social nuisance caused by urban motor ways and their noise. The Traffic Noise Index is used to indicate traffic noises and their effects on architectural designs and planning, while suggesting the need for more and better window insulation and acoustical barriers. Overall concern is for--(1)…

  3. Noise Pollution Control System in the Hospital Environment

    Figueroa Gallo, LM; Olivera, JM


    Problems related to environmental noise are not a new subject, but they became a major issue to solve because of the increasing, in complexity and intensity, of human activities due technological advances. Numerous international studies had dealt with the exposure of critical patients to noisy environment such as the Neonatal Intensive Care Units; their results show that there are difficulties in the organization in the developing brain, it can damage the delicate auditory structures and can cause biorhythm disorders, specially in preterm infants. The objective of this paper is to present the development and implementation of a control system that includes technical-management-training aspects to regulate the levels of specific noise sources in the neonatal hospitalization environment. For this purpose, there were applied different tools like: observations, surveys, procedures, an electronic control device and a training program for a Neonatal Service Unit. As a result, all noise sources were identified -some of them are eliminable-; all the service stable staff categories participated voluntarily; environmental noise measurements yielded values between 62.5 and 64.6 dBA and maximum were between 86.1 and 89.7 dBA; it was designed and installed a noise control device and the staff is being trained in noise reduction best practices.

  4. Structural Acoustic Prediction and Interior Noise Control Technology

    Mathur, G. P.; Chin, C. L.; Simpson, M. A.; Lee, J. T.; Palumbo, Daniel L. (Technical Monitor)


    This report documents the results of Task 14, "Structural Acoustic Prediction and Interior Noise Control Technology". The task was to evaluate the performance of tuned foam elements (termed Smart Foam) both analytically and experimentally. Results taken from a three-dimensional finite element model of an active, tuned foam element are presented. Measurements of sound absorption and sound transmission loss were taken using the model. These results agree well with published data. Experimental performance data were taken in Boeing's Interior Noise Test Facility where 12 smart foam elements were applied to a 757 sidewall. Several configurations were tested. Noise reductions of 5-10 dB were achieved over the 200-800 Hz bandwidth of the controller. Accelerometers mounted on the panel provided a good reference for the controller. Configurations with far-field error microphones outperformed near-field cases.

  5. Modern Approach in Management and Noise Control in Urban Areas

    Hadzi-Nikolova, Marija


    PhD thesis presents identification and analysis of noise sources in the city of Stip (as a representative for a small urban center with a dynamic development, whose noise dispersion model can be applied in other similar urban centers). Methodology for modern technologies application in management and noise control in urban areas is developed based on generated noise maps and conflicting noise maps. For this porpose, two-year noise level monitoring on strategic measurement points was performed...

  6. Noise transmission properties and control strategies for composite structures

    Silcox, Richard J.; Beyer, Todd B.; Lester, Harold C.


    A study of several component technologies required to apply active control techniques to reduce interior noise in composite aircraft structures is described. The mechanisms of noise transmission in an all composite, large-scale, fuselage model are studied in an experimental program and found similar to mechanisms found in conventional aircraft construction. Two primary conditions of structural acoustic response are found to account for the dominant interior acoustic response. A preliminary study of active noise control in cylinders used piezoceramic actuators as force inputs for a simple aluminum fuselage model. These actuators provided effective control for the same two conditions of noise transmission found in the composite fuselage structure. The use of piezoceramic actuators to apply force inputs overcomes the weight and structural requirements of conventional shaker actuators. Finally, in order to accurately simulate these types of actuators in a cylindrical shell, two analytical models are investigated that apply either in-plane forces or bending moments along the boundaries of a finite patch. It is shown that the bending model may not be as effective as the force model for exciting the low order azimuthal modes that typically dominate the structural acoustic response in these systems. This result will affect the arrangement and distribution of actuators required for effective active control systems.

  7. Noise control technology for generator sets in enclosures

    Nailong ZHANG; Wentong YANG; Renyuan FEI


    Currently, noise pollution is an environmental problem all over the world. The health and life of human beings are affected by loud noise from high power gen-erator sets. To reduce such noise, a sound-attenuated enclosure is widely used for its high performance and con-venient usage. By installing equipment in an enclosure, noise is controlled and prevented from radiating. In this paper, noise control techniques for enclosures are pre-sented. Enclosure development trends are predicted.

  8. Research on the application of active sound barriers for the transformer noise abatement

    Hu Sheng


    Full Text Available Sound barriers are a type of measure most commonly used in the noise abatement of transformers. In the noise abatement project of substations, the design of sound barriers is restrained by the portal frames which are used to hold up outgoing lines from the main transformers, which impacts the noise reduction effect. If active sound barriers are utilized in these places, the noise diffraction of sound barriers can be effectively reduced. At a 110kV Substation, an experiment using a 15-channel active sound barrier has been carried out. The result of the experiment shows that the mean noise reduction value (MNRV of the noise measuring points at the substation boundary are 1.5 dB (A. The effect of the active noise control system is impacted by the layout of the active noise control system, the acoustic environment on site and the spectral characteristic of the target area.

  9. Active noise cancellation in hearing devices


    Disclosed is a hearing device system comprising at least one hearing aid circuitry and at least one active noise cancellation unit, the at least one hearing aid circuitry comprises at least one input transducer adapted to convert a first audio signal to an electric audio signal; a signal processor...... connected to the at least one input transducer and adapted to process said electric audio signal by at least partially correcting for a hearing loss of a user; an output transducer adapted to generate from at least said processed electric audio signal a sound pressure in an ear canal of the user, whereby...... addition to said generated sound pressure, wherein the hearing device system further comprises a combiner unit adapted to combine the processed electric audio signal with the active noise cancellation signal, to obtain a combined signal and to provide the combined signal to the output transducer....

  10. Infinite non-causality in active cancellation of random noise

    Friot, E


    Active cancellation of broadband random noise requires the detection of the incoming noise with some time advance. In an duct for example this advance must be larger than the delays in the secondary path from the control source to the error sensor. In this paper it is shown that, in some cases, the advance required for perfect noise cancellation is theoretically infinite because the inverse of the secondary path, which is required for control, can include an infinite non-causal response. This is shown to be the result of two mechanisms: in the single-channel case (one control source and one error sensor), this can arise because of strong echoes in the control path. In the multi-channel case this can arise even in free field simply because of an unfortunate placing of sensors and actuators. In the present paper optimal feedforward control is derived through analytical and numerical computations, in the time and frequency domains. It is shown that, in practice, the advance required for significant noise attenua...

  11. The Feasibility of Noise Control in a Soft Drink Plant

    Fouladi Dehaghi


    Full Text Available Background “Noise” can be defined as any unwanted sound. Soft drink plants, which produce the raw materials used in most carbonated beverage factories, are sources of noise. Objectives This study investigated the noise pollution present in a soft drink CO2 gas injection plant, in order to present noise control measures. Materials and Methods The instructions specified by the canadian center for occupational health and safety (CCOHS were followed during the noise study, and a sound level meter, CEL.450 calibrated with CEL-110.2 based on ISO-9612 methods, was used to record the sound pressure level (SPL at each grid point. SPL was determined in weighting scales A and C. and a noise survey map of equivalent SPLs was drawn for each part. Each part of the floor area of the soft drink factory where SPL exceeded 85 dBA was identified from the noise survey map to determine the causes of high levels of noise. In order to reduce noise level in each part, the absorption coefficient, transmission loss, and noise reduction rate were calculated in the proposed control area. Results According to the study results, noise levels in a CO2 plant’s house and control room ranged from 88 to 102 dB and 79 to 82 dB (A, respectively. In order to reduce the amount of emitted noise in the CO2 plant house and control room, a noise control plan was implemented in each part of the facility; it was met with effective results. Conclusions The findings of this investigation have clearly revealed that plant workers are at risk of developing noise-induced hearing loss. However, after the implementation of a noise control plan in each part of the facility, the noise dose received by workers has significantly decreased. The need to implement a noise conservation program was established.

  12. Design and Simulation of Adaptive Active Noise Control System for Aircraft Helmet%飞行头盔主动噪声控制系统的设计及仿真研究

    唐红; 王明皓; 吴凤霞


    Aiming at solving low frequency noise existing in cockpit,a design for adaptive active noise control system of aircraft helmet is proposed. Based on it,the filtered-XLMS algoritbm is simulated and analysed using MATLAB.The result shows that the effect of reducing aircraft noise on low frequency is very satisfactory with the scheme.%针对飞机驾驶舱内存在着大量的低频噪声,提出一种应用于飞行员头盔的自适应有源噪声控制系统设计方案,并在此基础上,利用MATLAB对FXLMS算法进行了仿真和性能分析。结果表明,此方案对飞机噪声低频段具有很好的降噪效果。

  13. Active compressor engine silencer reduces exhaust noise

    An active industrial silencer on a compressor engine at a Tenneco Gas station has reduced low-frequency 'rumbling' noise by 8 dB during trials while lowering backpressure about 90$. This 8 dB reduction of the piston firing frequency corresponds to a more than 80% decrease in emitted acoustic power. The silencing unit, installed on one of six engines at the station near Eden, N.Y., continues in operation. Based on the results, the manufacturer is identifying additional compressor sites for further tests. This paper reviews this project

  14. Research on Noise Control for Ventilators with Resonance


    A study was carried out to control the noise produced by the ventilators at the Luling coalmine, which had caused serious noise pollution to the residents living around the mine for a long time. The main noise source was found to be the dynamic noise at the outlet of the diffuser. The frequency of its peak value was 250 Hz. A special brick with a resonant frequency of 250 Hz was designed to eliminate this noise. The diffusion of a lower frequency noise has been successfully controlled by the installation of a noise-eliminating tower above the diffuser outlet. The detection results show that the noise in the nearby residential area has been lowered to an average 55.3dB(A) in the daytime from 69.8dB(A) and to 48.4dB(A) at night from 65.8dB(A).

  15. A Calculation of hydrodynamic noise of control valve on instrumentation and control system using smart plant

    It has been calculated characteristics of the control valve Instrumentation and Control Systems using Smart Plant software. This calculation is done in order to control the valve that will be installed as part of the instrumentation and control systems to provide the performance according to the design. The characteristics that have been calculated are Reynolds number factors which are related to the flow regime in the valve. Critical pressure factor, Valve Hydrodynamic cavitation and noise index. In this paper the discussion will be limited to matters relating to Hydrodynamic noise generation process using model of the instrumentation and control system in the plant design in yellow cake PIPKPP activities in 2012. The results of the calculation of the noise on the valves design are in the range between 9.58~70.1 dBA. (author)

  16. Compressor noise control begins with design--Part 1

    This paper describes the typical methods used by oil and gas pipeline companies to reduce the noise level associated with their pump and compressor stations. The common method is for the design engineer to specify an acceptable noise level at a specified distance. Unfortunately, the results by this method are rarely acceptable because vendors have not considered the effects of sound propagation outside the station, the owners have not considered the cumulative effect of various machinery, and there is little methodology available to distinguish the individual components which might be contributing the acoustically unacceptable noise levels in a multi-component system. This article stresses balanced noise control designs using noise control engineering

  17. Air injection vacuum blower noise control

    Mose, Tyler L.A.; Faszer, Andrew C. [Noise Solutions Inc. (Canada)], email:, email:


    Air injection vacuum blowers, with applications in waste removal, central vacuum systems, and aeration systems, are widely used when high vacuum levels are required. Noise generated by those blowers must be addressed for operator health and residential disturbance. This paper describes a project led by Noise Solutions Inc., to identify noise sources in a blower, and design and test a noise mitigation system. First the predominant noise sources in the blower must be determined, this is done with a sound level meter used to quantify the contribution of each individual noise source and the dominant tonal noise from the blower. Design of a noise abatement system must take into account constraints arising from blower mobile use, blower optimal performance, and the resulting overall vibration of the structure. The design was based on calculations from the sound attenuation of a reactive expansion chamber and two prototypes of custom silencers were then tested, showing a significant noise reduction both in total sound levels and tonal noise.

  18. Perforated fairings for landing gear noise control

    Boorsma, K.; Zhang, X; Molin, N.


    Landing gears of commercial aircraft make an important contribution to total aircraft noise in the approach configuration. Using fairings to shield components from high speed impingement reduces noise. Furthermore, perforating these fairings has been confirmed by flight tests to further enable noise reduction. Following a more fundamental study on the application of perforated fairings, a study has been performed to investigate and optimize the benefits of bleeding air through landing gear fa...

  19. Noise and control decoupling of Advanced LIGO suspensions

    Ground-based interferometric gravitational wave observatories such as Advanced LIGO must isolate their optics from ground vibrations with suspension systems to meet their stringent noise requirements. These suspensions typically have very high quality-factor resonances that require active damping. The sensor noise associated with this damping is a potential significant contributor to the sensitivity of these interferometers. This paper introduces a novel scheme for suspension damping that isolates much of this noise and permits greater amounts of damping. It also decouples the damping feedback design from the interferometer control. The scheme works by invoking a change from a local coordinate frame associated with each suspension, to a coordinate frame aligned with the interferometric readout. In this way, degrees of freedom invisible to the readout can employ effective, but noisy damping. The degree of freedom measured by the readout is then damped using low noise interferometer signals, eliminating the need to use the usual noisy sensors. Simulated and experimental results validate the concepts presented in this paper. (paper)

  20. Control source development for reduction of noise transmitted through a double panel structure

    Ho, Jen-Hsuan


    A double panel structure, which consists of two panels with air in between, is widely adopted in many applications such as aerospace, automotive industries, and buildings due to its low sound transmission at high frequencies, low heat transmission, and low weight. Nevertheless, the resonance of the cavity and the poor sound transmission loss at low frequencies limit the double panel’s noise control performance. Applying active structural acoustic control to the panels or active noise control ...

  1. Quality control in digital mammography: the noise components

    Leyton, Fernando [Universidade de Tarapaca, Arica (Chile). Centro de Estudios en Ciencias Radiologicas; Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Nogueira, Maria do Socorro, E-mail: mnogue@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Duran, Maria Paz [Clinica Alemana, Santiago (Chile). Dept. de Radiologia; Dantas, Marcelino, E-mail: [Industrias Nucleares do Brasil (INB), Caldas, MG (Brazil). Unidade de Tratamento de Minerios; Ubeda, Carlos, E-mail: cubeda@uta.c [Universidade de Tarapaca, Arica (Chile). Fac. de Ciencias de la Salud


    To measure the linearity of the detector and determine the noise components (quantum, electronic and structural noise) that contributed to losing image quality and to determine the signal noise ratio (SNR) and contrast noise ratio (CNR). This paper describes the results of the implementation of a protocol for quality control in digital mammography performed in two direct digital mammography equipment (Hologic, Selenia) in Santiago of Chile. Shows the results of linearity and noise analysis of the images which establishes the main cause of noise in the image of the mammogram to ensure the quality and optimize procedures. The study evaluated two digital mammography's Selenia, Hologic (DR) from Santiago, Chile. We conducted the assessment of linearity of the detector, the signal noise ratio, contrast noise ratio and was determined the contribution of different noise components (quantum, electronics and structural noise). Used different thicknesses used in clinical practice according to the protocol for quality control in digital mammography of Spanish society of medical physics and NHSBSP Equipment Report 0604 Version 3. The Selenia mammography software was used for the analysis of images and Unfors Xi detector for measuring doses. The mammography detector has a linear performance, the CNR and SNR did not comply with the Protocol for the thicknesses of 60 and 70 mm. The main contribution of the noise corresponds to the quantum noise, therefore it is necessary to adjust and optimize the mammography system. (author)

  2. External noise control in inherently stochastic biological systems.

    Zheng, Likun; Chen, Meng; Nie, Qing


    Biological systems are often subject to external noise from signal stimuli and environmental perturbations, as well as noises in the intracellular signal transduction pathway. Can different stochastic fluctuations interact to give rise to new emerging behaviors? How can a system reduce noise effects while still being capable of detecting changes in the input signal? Here, we study analytically and computationally the role of nonlinear feedback systems in controlling external noise with the presence of large internal noise. In addition to noise attenuation, we analyze derivatives of Fano factor to study systems' capability of differentiating signal inputs. We find effects of internal noise and external noise may be separated in one slow positive feedback loop system; in particular, the slow loop can decrease external noise and increase robustness of signaling with respect to fluctuations in rate constants, while maintaining the signal output specific to the input. For two feedback loops, we demonstrate that the influence of external noise mainly depends on how the fast loop responds to fluctuations in the input and the slow loop plays a limited role in determining the signal precision. Furthermore, in a dual loop system of one positive feedback and one negative feedback, a slower positive feedback always leads to better noise attenuation; in contrast, a slower negative feedback may not be more beneficial. Our results reveal interesting stochastic effects for systems containing both extrinsic and intrinsic noises, suggesting novel noise filtering strategies in inherently stochastic systems. PMID:23213267

  3. Flow and Noise Control: Review and Assessment of Future Directions

    Thomas, Russell H.; Choudhari, Meelan M.; Joslin, Ronald D.


    Technologies for developing radically new aerovehicles that would combine quantum leaps in cost, safety, and performance benefits with environmental friendliness have appeared on the horizon. This report provides both an assessment of the current state-of-the-art in flow and noise control and a vision for the potential gains to be made, in terms of performance benefit for civil and military aircraft and a unique potential for noise reduction, via future advances in flow and noise technologies. This report outlines specific areas of research that will enable the breakthroughs necessary to bring this vision to reality. Recent developments in many topics within flow and noise control are reviewed. The flow control overview provides succinct summaries of various approaches for drag reduction and improved maneuvering. Both exterior and interior noise problems are examined, including dominant noise sources, physics of noise generation and propagation, and both established and proposed concepts for noise reduction. Synergy between flow and noise control is a focus and, more broadly, the need to pursue research in a more concurrent approach involving multiple disciplines. Also discussed are emerging technologies such as nanotechnology that may have a significant impact on the progress of flow and noise control.

  4. 螺桨飞机舱内噪声地面模拟及其主动控制%Ground-simulation of Propeller Induced Airplane Cabin Noise and Its Active Control

    吴亚锋; 李江红; 戴杏珍


    This paper presents the analogized methods and the active controlexperiments of the cabin noise for a propeller airplane.In a Y7 test airplane,the cabin noise is analogized by an exciter to structure-borne noise and by a loudspeaker to air-borne noise.A multi-channel adaptive control system is developed and used to attenuate the analogized noise field and satisfied results are obtained in the controlled area.%本文介绍螺桨飞机舱内噪声的地面模拟方法和主动控制实验。在一架运七试验机上,激振器和扬声器分别被用来模拟由螺桨旋转在舱内引起的结构和气动噪声。一个多通道自适应控制系统被应用于该模拟声场的主动控制实验,并在控制区域取得了满意的降噪效果。

  5. Danish activities concerning noise in the environment (A)

    Ingerslev, Fritz

    The paper describes the administrative activities and the distribution between federal and local authorities. The importance of having a federal agency with highly qualified employees who can establish a superior national noise abatement strategy is stressed. The federal authority should represent...... the country in international collaboration. It is claimed that noise abatement will be diffuse and weak, if it is not based on a national strategy. The discussion of noise in the environment covers: external industrial noise, road traffic noise, and air traffic noise. The principles on which the...

  6. Cost effective noise control in the oil and gas industry

    Meredith, Dave [Kinetics Noise Control Inc. (United States)], email:


    Infrastructures in the oil and gas industry are often sources of excessive noise and vibration. This paper focuses on the work of Kinetics Noise Control, Inc. (KNC), an independent consulting firm specialized in corrective noise and vibration control products, to ensure that their clients' operations meet government and industry regulations. Using examples of different projects that KNC has been involved with in the oil and gas industry, the author presents new designs and approaches for reducing noise pollution. Noise and vibration control strategy should be integral parts of the concept design phase and aim at meeting regulatory requirements without loss of overall efficiency. To do this, specific elements, such as an extensive analysis of noise and vibration sources, site environmental conditions, the acoustics of the infrastructures, and of the materials used must be taken into account.

  7. Hybrid Active/Passive Jet Engine Noise Suppression System

    Parente, C. A.; Arcas, N.; Walker, B. E.; Hersh, A. S.; Rice, E. J.


    A novel adaptive segmented liner concept has been developed that employs active control elements to modify the in-duct sound field to enhance the tone-suppressing performance of passive liner elements. This could potentially allow engine designs that inherently produce more tone noise but less broadband noise, or could allow passive liner designs to more optimally address high frequency broadband noise. A proof-of-concept validation program was undertaken, consisting of the development of an adaptive segmented liner that would maximize attenuation of two radial modes in a circular or annular duct. The liner consisted of a leading active segment with dual annuli of axially spaced active Helmholtz resonators, followed by an optimized passive liner and then an array of sensing microphones. Three successively complex versions of the adaptive liner were constructed and their performances tested relative to the performance of optimized uniform passive and segmented passive liners. The salient results of the tests were: The adaptive segmented liner performed well in a high flow speed model fan inlet environment, was successfully scaled to a high sound frequency and successfully attenuated three radial modes using sensor and active resonator arrays that were designed for a two mode, lower frequency environment.

  8. Stability of Controlled Hamilton Systems Excited by Gaussian White Noise

    SHANG Mei; GUO Yong-xin; MEI Feng-xiang


    A new method is introduced in this paper. This method can be used to study the stability of controlled holonomic Hamilton systems under disturbance of Gaussian white noise. At first, the motion equation of controlled holonomic Hamilton systems excited by Gaussian noise is formulated. A theory to stabilize the system is provided. Finally, one example is given to illustrate the application procedures.

  9. Adaptive Intelligent Ventilation Noise Control Project

    National Aeronautics and Space Administration — To address the NASA need for quiet on-orbit crew quarters (CQ), Physical Optics Corporation (POC) proposes to develop a new Adaptive Intelligent Ventilation Noise...

  10. Adaptive Intelligent Ventilation Noise Control Project

    National Aeronautics and Space Administration — To address NASA needs for quiet crew volumes in a space habitat, Physical Optics Corporation (POC) proposes to develop a new Adaptive Intelligent Ventilation Noise...

  11. Hybrid Feedforward-Feedback Noise Control Using Virtual Sensors

    Bean, Jacob; Fuller, Chris; Schiller, Noah


    Several approaches to active noise control using virtual sensors are evaluated for eventual use in an active headrest. Specifically, adaptive feedforward, feedback, and hybrid control structures are compared. Each controller incorporates the traditional filtered-x least mean squares algorithm. The feedback controller is arranged in an internal model configuration to draw comparisons with standard feedforward control theory results. Simulation and experimental results are presented that illustrate each controllers ability to minimize the pressure at both physical and virtual microphone locations. The remote microphone technique is used to obtain pressure estimates at the virtual locations. It is shown that a hybrid controller offers performance benefits over the traditional feedforward and feedback controllers. Stability issues associated with feedback and hybrid controllers are also addressed. Experimental results show that 15-20 dB reduction in broadband disturbances can be achieved by minimizing the measured pressure, whereas 10-15 dB reduction is obtained when minimizing the estimated pressure at a virtual location.

  12. Aeroacoustics of Flight Vehicles: Theory and Practice. Volume 2: Noise Control

    Hubbard, Harvey H. (Editor)


    Flight vehicles and the underlying concepts of noise generation, noise propagation, noise prediction, and noise control are studied. This volume includes those chapters that relate to flight vehicle noise control and operations: human response to aircraft noise; atmospheric propagation; theoretical models for duct acoustic propagation and radiation; design and performance of duct acoustic treatment; jet noise suppression; interior noise; flyover noise measurement and prediction; and quiet aircraft design and operational characteristics.

  13. Barkhausen noise sensor with direct field control

    Stupakov, Oleksandr


    Roč. 11, č. 1 (2013), s. 209-212. ISSN 1546-198X R&D Projects: GA ČR GP102/09/P108 Institutional research plan: CEZ:AV0Z10100520 Keywords : Barkhausen noise * field measurement * magnetic non-destructive testing Subject RIV: JB - Sensor s, Measurment, Regulation Impact factor: 0.558, year: 2013

  14. Application of an active device for helicopter noise reduction in JAXA

    Saito, Shigeru; Kobiki, Noboru; Tanabe, Yasutada [Japan Aerospace Exploration Agency (JAXA), 7-44-1 Jindaiji Higashi-machi, Chofu, Tokyo 182-8522 (Japan)], E-mail:


    Important issues in noise problems for current helicopters are described. An active tab (AT) was developed as a new active device for noise/vibration reduction under research cooperation between Japan Aerospace Exploration Agency (JAXA) and Kawada Industries, Inc. The wind tunnel test was conducted in order to investigate the effectiveness of the AT on the aeroacoustic characteristics of a helicopter. From the wind tunnel test, the capability of reducing blade vortex interaction (BVI) noise by an AT was verified. A new control law using instantaneous pressure change on a blade during BVI phenomena was introduced and applied to the wind tunnel testing. This new control law shows reasonable controllability for helicopter noise reduction. Furthermore, in order to analyze noise characteristics, the advanced computational fluid dynamics (CFD) code named JAXA{sub o}v3d was developed in JAXA and extended to include CFD-CSD (computational structure dynamics) coupling by using the beam theory for blade deformation. (invited paper)

  15. Application of an active device for helicopter noise reduction in JAXA

    Important issues in noise problems for current helicopters are described. An active tab (AT) was developed as a new active device for noise/vibration reduction under research cooperation between Japan Aerospace Exploration Agency (JAXA) and Kawada Industries, Inc. The wind tunnel test was conducted in order to investigate the effectiveness of the AT on the aeroacoustic characteristics of a helicopter. From the wind tunnel test, the capability of reducing blade vortex interaction (BVI) noise by an AT was verified. A new control law using instantaneous pressure change on a blade during BVI phenomena was introduced and applied to the wind tunnel testing. This new control law shows reasonable controllability for helicopter noise reduction. Furthermore, in order to analyze noise characteristics, the advanced computational fluid dynamics (CFD) code named JAXAov3d was developed in JAXA and extended to include CFD-CSD (computational structure dynamics) coupling by using the beam theory for blade deformation. (invited paper)

  16. INVITED PAPER: Application of an active device for helicopter noise reduction in JAXA

    Saito, Shigeru; Kobiki, Noboru; Tanabe, Yasutada


    Important issues in noise problems for current helicopters are described. An active tab (AT) was developed as a new active device for noise/vibration reduction under research cooperation between Japan Aerospace Exploration Agency (JAXA) and Kawada Industries, Inc. The wind tunnel test was conducted in order to investigate the effectiveness of the AT on the aeroacoustic characteristics of a helicopter. From the wind tunnel test, the capability of reducing blade vortex interaction (BVI) noise by an AT was verified. A new control law using instantaneous pressure change on a blade during BVI phenomena was introduced and applied to the wind tunnel testing. This new control law shows reasonable controllability for helicopter noise reduction. Furthermore, in order to analyze noise characteristics, the advanced computational fluid dynamics (CFD) code named JAXA_ov3d was developed in JAXA and extended to include CFD-CSD (computational structure dynamics) coupling by using the beam theory for blade deformation.

  17. Effect of individual blade control on noise radiation

    Swanson, S. M.; Jacklin, Stephen A.; Niesl, G.; Blaas, Achim; Kube, R.


    In a joint research program of NASA Ames Research Center, ZF Luftfahrttechnik, the German Aerospace Research Establishment (DLR), and EUROCOPTER Deutschland, a wind tunnel test was performed to evaluate the effects of Individual Blade Control (IBC) on rotor noise. This test was conducted in the 40x80 ft wind tunnel at NASA Ames Research Center, utilizing a full scale MBB-BO 105 four-bladed rotor system. Three microphones were installed for determination of the radiated noise, two of them on a moveable traverse below the advancing blade side and one in a fixed location below the retreating side. Acoustic results are presented for flight conditions with Blade-Vortex-Interaction (BVI) noise radiation. High noise level reductions were measured for single harmonic control inputs. In addition to the single harmonic inputs, multi-harmonic inputs were evaluated by superimposing 2/rev to 6/rev harmonics. For the first time the efficiency of sharp wavelets (60 deg and 90 deg width) on acoustic noise were measured. In order to achieve an adequate wavelet shape at the blade tip, corrections were made to account for the blade torsional behavior. In parallel with the acoustic measurements, vibratory loads were measured during the BVI flight condition to correlate the effects of IBC on noise and vibrations. It is shown how noise levels and vibrations are affected by specific IBC control inputs. In addition, correlations are made between noise levels and acoustic time histories with IBC phase and amplitude variations. For one IBC input mode with high noise reducing efficiency, a sweep of the moveable microphone traverse below the advancing side shows the effect on BVI noise directivity.

  18. Inter-noise 85; Proceedings of the Fourteenth International Conference on Noise Control Engineering, Munich, West Germany, September 18-20, 1985. Volumes 1 & 2

    Various papers on the problem of noise are presented. The general topics addressed include: sources of noise emission; physical phenomena associated with noise; noise control elements; and the generation, transmission, isolation, and reduction of vibrations. Individual subjects discussed include: regulation and technical standards of noise control; noise-induced health disturbances; principles of machine noise reduction; characteristics and prediction of factory sound propagation; reduction of structure-borne noise; noise prediction and planning; noise emission data of machines and equipment; noise emission from road vehicles; noise from general aviation aircraft; noise emission from jet aircraft during takeoff; damping and acoustical radiation efficiency of carbon fiber-reinforced carbon epoxy plates.

  19. Compressor noise control begins with design--Part 2

    Reduction of noise pollution at gas compressor stations associated with natural gas pipelines and distribution systems, has long been a complex problem. Specified noise levels of individual components tell nothing of the overall system when it is installed and placed in a site-specific setting. Further, testing for compliance performance guarantees is virtually impossible to conduct at a distant location because one cannot distinguish among various contributing noise sources. This paper develops a plan for calculating an estimate of sound generation from a compressor station and the methods for controlling and measuring sounds of individual components. It also classifies the types of noise and gives various methods of dealing with each noise type

  20. Control Quality of a Feedback Control System under Cyclostationary Noise in Power Line Communication

    Carrizo, Cesar; Kobayashi, Kentaro; Okada, Hiraku; Katayama, Masaaki

    This paper discusses a control system that employs a power line to transfer signals to control the motion of a single machine, and explores the influence of packet losses on the quality of the control. As an example of a controlled system, a controller with a rotary inverted pendulum as a controlled object, is considered. The feedback loop in between is the power line. The control performance is evaluated in the power line cyclostationary noise environment and compared against the performance in a stationary noise environment. As a result, it is confirmed that the power line and its cyclostationary noise features present an advantage against transmission in a channel with stationary noise.

  1. Environmental noise alters gastric myoelectrical activity: Effect of age

    James S Castle; Jin-Hong Xing; Mark R Warner; Mark A Korsten


    AIM: To evaluate the effect of age and acoustic stress on gastric myoelectrical activity (GMA) and autonomic nervous system function,METHODS: Twenty-one male subjects (age range 22-71years, mean 44 years) were recruited and exposed, in random order, to three auditory stimuli (Hospital noise,conversation babble and traffic noise) after a 20-min baseline. All periods lasted 20 min and were interspersed with a 10 min of recovery. GMA was obtained using a Synectics Microdigitrapper. Autonomic nerve function was assessed by monitoring blood pressure and heart rate using an automatic recording device.RESULTS: Dominant power tended to decrease with increase of age (P<0.05). The overall percentage of three cycle per minute (CPM) activity decreased during exposure to hospital noise (12.0%, P < 0.05), traffic noise (13.9%, P < 0.05), and conversation babble(7.1%). The subjects in the younger group (< 50 years)showed a consistent reduction in the percentage of 3CPM activity during hospital noise (22.9%, P < 0.05),traffic noise (19.0%, P < 0.05), and conversation babble(15.5%). These observations were accompanied by a significant increase in bradygastria: hospital noise (P< 0.05) and traffic noise (P < 0.05). In contrast, the subjects over 50 years of age did not exhibit a significant decrease in 3 CPM activity. Regardless of age, noise did not alter blood pressure or heart rate.CONCLUSION: GMA changes with age. Loud noise can alter GMA, especially in younger individuals. Our data indicate that even short-term exposure to noise may alter the contractility of the stomach.

  2. Legal and planning framework for the control of noise emissions

    An examination of the statutory basis for the control of noise emissions is presented. Principal pieces of United Kingdom legislation and some advisory notes have been produced within 6 extensive appendices. The paper briefly examines the controls in other EC countries before discussing the way in which planning controls in the United Kingdom relate to the jurisdiction of the court. (author)

  3. Legal and planning framework for the control of noise emissions

    An examination is offered of the statutory basis for the control of noise emissions. Principal pieces of legislation and some advisory notes have been produced within appendices. The paper briefly examines the controls in other EC countries before discussing the way in which planning controls relate to the jurisdiction of the court. (author)

  4. Noise, Worker Perception, and Worker Concentration in Timber Harvesting Activity

    Efi Yuliati Yovi


    Full Text Available Timber harvesting activities are unquestionably related with high risk of work accidents and health disorders.Such activities were not only burdened the workers with heavy physical workloads due to uneasy workingenvironment, and massive work materials and tools, but also physiopsychologically burdened workers as theywere imposed with both mechanical and acoustic vibrations (noise produced by the chainsaw. However,  it is acommon practice that most of the workers still ignored the importance of the use of noise reduction devices suchas earmuff or ear plug.  This study was aimed to reveal the factual effects of noise on work concentration of theworkers to provide a scientific basis in supporting efforts in improving workers’ attitude.  The results confirmedthat chainsaw might produce noise during operation.  Noise intensities received by both right and left ears werenot significantly different, indicating that left-handed and normal workers received similar degree of noise inboth side of ears. Further, results also showed that there was a significant difference on the perception and workconcentration of chainsaw operators versus sedentary people to the noise.  These findings proved that hearingability of chainsaw operators had declined due to frequent noise exposure.Keywords: timber harvesting, physio-psychological disorder, noise, chainsaw

  5. Inter-noise 89 - Engineering for environmental noise control; Proceedings of the International Conference on Noise Control Engineering, Newport Beach, CA, Dec. 4-6, 1989. Vols. 1 & 2

    Maling, George C., Jr.

    Recent advances in noise analysis and control theory and technology are discussed in reviews and reports. Topics addressed include noise generation; sound-wave propagation; noise control by external treatments; vibration and shock generation, transmission, isolation, and reduction; multiple sources and paths of environmental noise; noise perception and the physiological and psychological effects of noise; instrumentation, signal processing, and analysis techniques; and noise standards and legal aspects. Diagrams, drawings, graphs, photographs, and tables of numerical data are provided.

  6. Performance Analysis of Transfer function Based Active Noise Cancellation Method Using Evolutionary Algorithm

    Prof. Vikas Gupta


    Full Text Available Due to the exponential increase of noise pollution, the demand for noise controlling system is also increases. Basically two types of techniques are used for noise cancellation active and passive. But passive techniques are inactive for low frequency noise, hence there is an increasing demand of research and developmental work on active noise cancellation techniques. In this paper we introduce a new method in the active noise cancellation system. This new method is the transfer function based method which used Genetic and Particle swarm optimization (PSO algorithm for noise cancellation. This method is very simple and efficient for low frequency noise cancellation. Here we analysis the performance of this method in the presence of white Gaussian noise and compare the results of Particle swarm optimization (PSO and Genetic algorithm. Both algorithms are suitable for different environment, so we observe their performance in different fields. In this paper a comparative study of Genetic and Particle swarm optimization (PSO is described with proper results. It will go in depth what exactly transfer function method, how it work and advantages over neural network based method

  7. Control of noise - systems for compact HVAC units

    Pedersen, Steffen; Møller, Henrik


    This paper discusses noise control systems for implementation in compact HVAC units. The control of low-frequency noise presents different problems than at higher frequencies. This is mainly related to the long wavelength, which means that passive solutions require a significant volume of space...... systems affect the performance of implementations. The source pressure and the impedance of a centrifugal fan were measured, and a number of configurations for noise control were investigated. The performance of a simple analogue feedback control was tested in a physical prototype. An adaptive digital...... controller (feedback and feedforward using FXLMS with cancellation of feedback to reference) was simulated and implemented on a low-cost TI C55XX DSP platform....

  8. Noise controlled synchronization in potassium coupled neural models

    Postnov, Dmitry E; Ryazanova, Ludmila S; Zhirin, Roman A;


    The paper applies biologically plausible models to investigate how noise input to small ensembles of neurons, coupled via the extracellular potassium concentration, can influence their firing patterns. Using the noise intensity and the volume of the extracellular space as control parameters, we...... show that potassium induced depolarization underlies the formation of noise-induced patterns such as delayed firing and synchronization. These phenomena are associated with the appearance of new time scales in the distribution of interspike intervals that may be significant for the spatio...

  9. Design and control of noise-induced synchronization patterns

    Kurebayashi, Wataru; Hasegawa, Mikio; Nakao, Hiroya


    We propose a method for controlling synchronization patterns of limit-cycle oscillators by common noisy inputs, i.e., by utilizing noise-induced synchronization. Various synchronization patterns, including fully synchronized and clustered states, can be realized by using linear filters that generate appropriate common noisy signals from given noise. The optimal linear filter can be determined from the linear phase response property of the oscillators and the power spectrum of the given noise. The validity of the proposed method is confirmed by numerical simulations.

  10. Studying the Noise Control Engineering Protocols in Industry

    Hamid Golshah


    Full Text Available Today, sound is one of the detrimental factors in the workplace and its harmful impact has been so important that scientists have named it “Noise Pollutions”. Hearing is one of the five senses of human being which is also a medium for communicating with other s and enjoying the pleasant feeling of listening to a piece of music. In spite of this, changes in the intensity and frequency of sound can make it annoying. Using Sound Level Meter to measure the dB of noise in the workplace and noise control principles will be discussed here.

  11. Process controlled data acquisition in the measurement of noise

    For the calibration of noise standards the output signal of a standard measuring system has to be recorded and averaged over large time intervals. The output signal is a low-frequency noise signal, which is recorded with a fast data acquisition system, using a Siemens on-line computer. This system is also used for data processing and for the evaluation of parameters to control the standard measuring system. (orig./RW)

  12. Tunable Interior Rotorcraft Noise Control Project

    National Aeronautics and Space Administration — CRG has recently developed a new class of shape memory polymers (SMP) that are electrically activated, as opposed to the more mature thermally activated SMPs....

  13. Adjoint-based sensitivity and feedback control of noise emission

    Airiau, Christophe


    A LQR control is performed on a reduce order model built from Direct Numerical Simulation of an open cavity flow, for a 2D geometry, and in the aim of controlling noise emission. A -10 dB achievement is demonstrated

  14. Effects of Noise on Asymmetric Bidirectional Controlled Teleportation

    Nie, Yi-you; Sang, Ming-huang


    We present a scheme for asymmetric bidirectional controlled teleportation via a six-qubit cluster state in noisy environments, which includes the phase-damping and amplitude-damping channels. We analytically derive the fidelities of the asymmetric bidirectional controlled teleportation process in these two noise channels. We show that the fidelities only depend on the initial state and the noisy rate.

  15. Updating working memory in aircraft noise and speech noise causes different fMRI activations.

    Saetrevik, Bjørn; Sörqvist, Patrik


    The present study used fMRI/BOLD neuroimaging to investigate how visual-verbal working memory is updated when exposed to three different background-noise conditions: speech noise, aircraft noise and silence. The number-updating task that was used can distinguish between "substitution processes," which involve adding new items to the working memory representation and suppressing old items, and "exclusion processes," which involve rejecting new items and maintaining an intact memory set. The current findings supported the findings of a previous study by showing that substitution activated the dorsolateral prefrontal cortex, the posterior medial frontal cortex and the parietal lobes, whereas exclusion activated the anterior medial frontal cortex. Moreover, the prefrontal cortex was activated more by substitution processes when exposed to background speech than when exposed to aircraft noise. These results indicate that (a) the prefrontal cortex plays a special role when task-irrelevant materials should be denied access to working memory and (b) that, when compensating for different types of noise, either different cognitive mechanisms are involved or those cognitive mechanisms that are involved are involved to different degrees. PMID:25352319

  16. Comparison of speech intelligibility in cockpit noise using SPH-4 flight helmet with and without active noise reduction

    Chan, Jeffrey W.; Simpson, Carol A.


    Active Noise Reduction (ANR) is a new technology which can reduce the level of aircraft cockpit noise that reaches the pilot's ear while simultaneously improving the signal to noise ratio for voice communications and other information bearing sound signals in the cockpit. A miniature, ear-cup mounted ANR system was tested to determine whether speech intelligibility is better for helicopter pilots using ANR compared to a control condition of ANR turned off. Two signal to noise ratios (S/N), representative of actual cockpit conditions, were used for the ratio of the speech to cockpit noise sound pressure levels. Speech intelligibility was significantly better with ANR compared to no ANR for both S/N conditions. Variability of speech intelligibility among pilots was also significantly less with ANR. When the stock helmet was used with ANR turned off, the average PB Word speech intelligibility score was below the Normally Acceptable level. In comparison, it was above that level with ANR on in both S/N levels.

  17. Voice communications in the cockpit noise environment: The role of active noise reduction

    Wheeler, Peter David

    The topic of voice communications in the cockpit noise environment of modern fast-jet aircraft and helicopters is addressed, and in particular, research undertaken in support of the development of a system for reducing the noise level at the operators' ear is described by acoustic cancellation within the ear defender, known as active noise reduction (ANR). The internal noise spectra of today's high performance fast-jet aircraft and military helicopters is described, and the complex interaction of acoustic noise transmission, speech, and microphone noise pick-up, which produces the total acoustic environment at the aircrews' ears, is discussed. Means of mathematically modelling the audio channel, quantifying the components identified above, and identifying areas of shortfall in performance are derived, leading to a procedure for the development of attenuation requirements, described as the communications audit. A model of the electroacoustic characteristics of the ANR ear defender assembly is presented and the sound field distribution within the ear defender/ear cavity, and its effect upon cancellation performance, is discussed. The extensive laboratory and flight testing of the ANR system that was undertaken is reviewed, paying particular attention to the measurement and analysis techniques employed in such testing. Finally, the performance characteristics of ANR are discussed and compared with the requirements previously established. Design limitations placed upon the system by the constraints of its area of application are described, and the scope for future improvements is considered.

  18. Controlling low frequency noise using a passive silencer

    DeGagne, D.C.; Faszer, A.C. [Noise Solutions Inc., Calgary, AB (Canada)


    Nearly 85 per cent of all the oil and natural gas recovered in Canada comes from Alberta where noise emissions from energy facilities are regulated by the Energy Resources Conservation Board (ERCB) and the Alberta Utilities Commission (AUC) through Noise Control Directive D-038. Operators of energy facilities in Alberta must meet the Permissible Sound Level (PSL) established for industrial facilities that are established for receptor locations such as nearby residences. Despite efforts to manage noise, complaints from nearby residents continue to occur even if the facility is in compliance. This is because high and mid frequency components can decay or be absorbed by air and ground conditions leaving mostly low frequency noise (LFN) at the residence. This paper explored the significance of LFN and how some facility operators are dealing with this problem. The impacts of LFN can range from creating a sensation of pressure in the ear, disturbing normal conversation, to creating secondary vibrating effects within homes. If severe enough, it can also result in potential behavioural dysfunction such as task performance deterioration, sleep disturbance and headaches. In 2006, Noise Solutions Inc. was approached by Hunt Oil Company regarding the installation of a new compressor at their Caroline site. The proposal posed a serious noise problem for the community which requested that the new compressor unit be developed without any additional noise impact on the area. Noise Solutions Inc. used a multi-phased approach to develop the most effective LFN silencer using best practical technology and materials. In an effort to fully attenuate both the high frequency noise (dBA) and the low frequency noise (dBC) of the new compressor unit, Noise Solutions and Hunt Oil agreed that a significant level of sound-suppression would be necessary. The entire noise-suppression unit was specially designed to compensate for the sheer size of the compressor building. The first step to

  19. Noise

    Noise is all around you, from televisions and radios to lawn mowers and washing machines. Normally, you ... sensitive structures of the inner ear and cause noise-induced hearing loss. More than 30 million Americans ...

  20. Noise Control in Gene Regulatory Networks with Negative Feedback.

    Hinczewski, Michael; Thirumalai, D


    Genes and proteins regulate cellular functions through complex circuits of biochemical reactions. Fluctuations in the components of these regulatory networks result in noise that invariably corrupts the signal, possibly compromising function. Here, we create a practical formalism based on ideas introduced by Wiener and Kolmogorov (WK) for filtering noise in engineered communications systems to quantitatively assess the extent to which noise can be controlled in biological processes involving negative feedback. Application of the theory, which reproduces the previously proven scaling of the lower bound for noise suppression in terms of the number of signaling events, shows that a tetracycline repressor-based negative-regulatory gene circuit behaves as a WK filter. For the class of Hill-like nonlinear regulatory functions, this type of filter provides the optimal reduction in noise. Our theoretical approach can be readily combined with experimental measurements of response functions in a wide variety of genetic circuits, to elucidate the general principles by which biological networks minimize noise. PMID:27095600

  1. Control of ground-borne noise and vibration

    Wilson, G. P.; Saurenman, H. J.; Nelson, J. T.


    Ground-borne noise and vibration created by train operations is one of the major environmental problems faced by rail transit systems. In the past 10-20 years there have been a number of developments in the control and prediction of ground-borne noise and vibration although it is evident that further research is needed. In this paper the focus is on two methods of controlling the vibration radiated by the transit structure. First is the use of floating slab trackbeds, a method that has proven to be very effective at reducing vibration at frequencies above the resonance frequency of the floating slab system. Second is to modify the design of transit car bogies such that the wheel/rail forces are reduced. Although this method is still in the exploratory phase it has been shown that proper design of the bogie suspension can significantly reduce the levels of ground-borne noise and vibration.

  2. Neural control of helicopter blade-vortex interaction noise

    Glaessel, Holger; Kloeppel, Valentin; Rudolph, Stephan


    Significant reduction of helicopter blade-vortex interaction (BVI) noise is currently one of the most advanced research topics in the helicopter industry. This is due to the complex flow, the close aerodynamic and structural coupling, and the interaction of the blades with the trailing edge vortices. Analytical and numerical modeling techniques are therefore currently still far from a sufficient degree of accuracy to obtain satisfactory results using classical model based control concepts. Neural networks with a proven potential to learn nonlinear relationships implicitly encoded in a training data set are therefore an appropriate and complementary technique for the alternative design of a nonlinear controller for BVI noise reduction. For nonlinear and adaptive control different neural control strategies have been proposed. Two possible approaches, a direct and an indirect neural controller are described. In indirect neural control, the plant has to be identified first by training a network with measured data. The plant network is then used to train the controller network. On the other hand the direct control approach does not rely on an explicit plant model, instead a specific training algorithm (like reinforcement learning) uses the information gathered from interactions with the environment. In the investigation of the BVI noise phenomena, helicopter developers have undertaken substantial efforts in full scale flight tests and wind tunnel experiments. Data obtained in these experiments have been adequately preprocessed using wavelet analysis and filtering techniques and are then used in the design of a neural controller. Neural open-loop control and neural closed-loop control concepts for the BVI noise reduction problem are conceived, simulated and compared against each other in this work in the above mentioned framework.

  3. White noise improves learning by modulating activity in dopaminergic midbrain regions and right superior temporal sulcus.

    Rausch, Vanessa H; Bauch, Eva M; Bunzeck, Nico


    In neural systems, information processing can be facilitated by adding an optimal level of white noise. Although this phenomenon, the so-called stochastic resonance, has traditionally been linked with perception, recent evidence indicates that white noise may also exert positive effects on cognitive functions, such as learning and memory. The underlying neural mechanisms, however, remain unclear. Here, on the basis of recent theories, we tested the hypothesis that auditory white noise, when presented during the encoding of scene images, enhances subsequent recognition memory performance and modulates activity within the dopaminergic midbrain (i.e., substantia nigra/ventral tegmental area, SN/VTA). Indeed, in a behavioral experiment, we can show in healthy humans that auditory white noise-but not control sounds, such as a sinus tone-slightly improves recognition memory. In an fMRI experiment, white noise selectively enhances stimulus-driven phasic activity in the SN/VTA and auditory cortex. Moreover, it induces stronger connectivity between SN/VTA and right STS, which, in addition, exhibited a positive correlation with subsequent memory improvement by white noise. Our results suggest that the beneficial effects of auditory white noise on learning depend on dopaminergic neuromodulation and enhanced connectivity between midbrain regions and the STS-a key player in attention modulation. Moreover, they indicate that white noise could be particularly useful to facilitate learning in conditions where changes of the mesolimbic system are causally related to memory deficits including healthy and pathological aging. PMID:24345178

  4. Adaptive Feed-Forward Control of Low Frequency Interior Noise

    Kletschkowski, Thomas


    This book presents a mechatronic approach to Active Noise Control (ANC). It describes the required elements of system theory, engineering acoustics, electroacoustics and adaptive signal processing in a comprehensive, consistent and systematic manner using a unified notation. Furthermore, it includes a design methodology for ANC-systems, explains its application and describes tools to be used for ANC-system design. From the research point of view, the book presents new approaches to sound source localization in weakly damped interiors. One is based on the inverse finite element method, the other is based on a sound intensity probe with an active free field. Furthermore, a prototype of an ANC-system able to reach the physical limits of local (feed-forward) ANC is described. This is one example for applied research in ANC-system design. Other examples are given for (i) local ANC in a semi-enclosed subspace of an aircraft cargo hold and (ii) for the combination of audio entertainment with ANC.

  5. Noise and Sound Control in Open Plan Schools.

    Schellenberg, Ben

    This annotated bibliography includes summaries of 19 articles and reports dealing with noise control and acoustical design in school buildings. A brief introduction discusses the need for careful attention to acoustics in any school construction or remodeling project, with particular emphasis on the need for special acoustical measures in an open…

  6. The Effect of fMRI (Noise) on Cognitive Control

    Hommel, Bernhard; Fischer, Rico; Colzato, Lorenza S.; van den Wildenberg, Wery P. M.; Cellini, Cristiano


    Stressful situations, the aversiveness of events, or increases in task difficulty (e.g., conflict) have repeatedly been shown to be capable of triggering attentional control adjustments. In the present study we tested whether the particularity of an fMRI testing environment (i.e., EPI noise) might result in such increases of the cognitive control…

  7. Collisional activation with random noise in ion trap mass spectrometry

    McLuckey, S.A.; Goeringer, D.E.; Glish, G.L. [Oak Ridge National Lab., TN (United States)


    Random noise applied to the end caps of a quadrupole ion trap is shown to be an effective means for the collisional activation of trapped ions independent of mass/charge ratio and number of ions. This technique is compared and contrasted with conventional single-frequency collisional activation for the molecular ion of N,N-dimethylaniline, protonated cocaine, the molecular anion of 2,4,6-trinitrotoluene, and doubly protonated neuromedin U-8. Collisional activation with noise tends to produce more extensive fragmentation than the conventional approach due to the fact that product ions are also kinetically excited in the noise experiment. The efficiency of the noise experiment in producing detectable product ions relative to the conventional approach ranges from being equivalent to being a factor of 3 less efficient. Furthermore, discrimination against low mass/charge product ions is apparent in the data from multiply charged biomolecules. Nevertheless, collisional activation with random noise provides a very simple means for overcoming problems associated with the dependence of single-frequency collisional activation on mass/charge ratio and the number of ions in the ion trap. 45 refs., 7 figs.

  8. Transparent sound screens. [and their noise control efficiency in buildings

    Bizo, F.; Draghici, R.


    Transparent sound screens consisting of glass (organic glass) plates placed at fixed angles with respect to the floor are considered. Noise levels in the screened area depend on the cumulative effect of direct, reverberated and refracted components of sound energy radiated by the source. This effect is analyzed on the analogy of the summation of electrical impedances. Inasmuch as under given circumstances sufficient noise control can be obtained, transparent screens seem to solve the problem of unimpeded supervision of installations in noisy workshops and power plants; in administrative buildings, computing centers, design bureaus, etc., they ensure acoustic comfort without space losses and without inspiring claustrophobia.

  9. Exoemissive noise activity of different metallic materials

    Bichevin, V.; Käämbre, H.; Sammelselg, V.; Kelle, H.; Asari, E.; Saks, O.


    A method is proposed for testing the exoemission activity of different metals, used as materials in high sensitivity electrometry (attoammetry). The presented test results allow us to select materials with weaker exoelectron spurious currents.

  10. Assuring robustness to noise in optimal quantum control experiments

    Closed-loop optimal quantum control experiments operate in the inherent presence of laser noise. In many applications, attaining high quality results [i.e., a high signal-to-noise (S/N) ratio for the optimized objective] is as important as producing a high control yield. Enhancement of the S/N ratio will typically be in competition with the mean signal, however, the latter competition can be balanced by biasing the optimization experiments towards higher mean yields while retaining a good S/N ratio. Other strategies can also direct the optimization to reduce the standard deviation of the statistical signal distribution. The ability to enhance the S/N ratio through an optimized choice of the control is demonstrated for two condensed phase model systems: second harmonic generation in a nonlinear optical crystal and stimulated emission pumping in a dye solution

  11. Thermally activated switching in the presence of non-Gaussian noise

    Billings, Lora; Dykman, Mark I.; Schwartz, Ira B.


    We study the effect of a non-Gaussian noise on interstate switching activated primarily by Gaussian noise. Even weak non-Gaussian noise can strongly change the switching rate. The effect is determined by all moments of the noise distribution. The explicit analytical results are compared with the results of simulations for an overdamped system driven by white Gaussian noise and a Poisson noise. Switching induced by a purely Poisson noise is also discussed.

  12. Region-based active contour with noise and shape priors

    Lecellier, François; Fadili, Jalal; Aubert, Gilles; Revenu, Marinette; Saloux, Eric


    In this paper, we propose to combine formally noise and shape priors in region-based active contours. On the one hand, we use the general framework of exponential family as a prior model for noise. On the other hand, translation and scale invariant Legendre moments are considered to incorporate the shape prior (e.g. fidelity to a reference shape). The combination of the two prior terms in the active contour functional yields the final evolution equation whose evolution speed is rigorously derived using shape derivative tools. Experimental results on both synthetic images and real life cardiac echography data clearly demonstrate the robustness to initialization and noise, flexibility and large potential applicability of our segmentation algorithm.

  13. Effects of time delay and noise correlation on noise enhanced stability and resonant activation in a periodically modulated bistable system

    This work analyzes numerically the effects of delay time τ and cross-correlation strength between noises λ on the phenomena of noise enhanced stability (NES) and resonant activation (RA) in a periodically modulated bistable system. The simulation results indicate that: (i) multiplicative noise can produce the NES effect only for the larger λ, while additive noise always induces the NES effect; (ii) for the NES phenomenon induced by additive noise, there is a characteristic value of τ, below which the increasing of τ enhances it and above which the effect of τ reverses; however, the increasing of τ can only enhance the NES effect induced by multiplicative noise; (iii) increasing λ weakens the NES effect induced by additive noise and strengthens that induced by multiplicative noise; and (iv) the RA effect becomes more and more pronounced while the RA minimum of the mean first-passage time increases with the increase of λ or τ. (paper)

  14. Design of Low Noise 16-bit CMOS Digitally Controlled Oscillator

    Nitin Kumar


    Full Text Available In this paper, a new differential delay cell is proposed and 16-bit Digital Controlled Oscillator (DCO based on proposed delay cell is designed. The 16-bit DCO consist of 4-stages differential delay cell in ring structure and a digital control scheme has been used to improved noise characteristics. The structure of the DCO utilizes dual delay path techniques to achieve high oscillation frequency and awide tuning range. The DCO circuit has been simulated in SPICE with 0.5μm technology operating with supply voltage of 5V. DCO achieved a controllable frequency range of [1.7324-4.8649] GHz with a tuningrange of 3.1325GHz (≈64%. The measured output noise is -161.2dB/Hz and the total harmonic distortion have been found 75.4865dB with 6666H control word. The phase noise in proposed DCO design is -179.4dB/Hz at a frequency of 1.7324GHz.

  15. BVI induced vibration and noise alleviation by active and passive approaches

    Liu, Li

    This dissertation describes the development of a comprehensive aeroelastic/aeroacoustic simulation capability for the modeling of vibration and noise in rotorcraft induced by blade-vortex interaction (BVI). Subsequently this capability is applied to study vibration and noise reduction, using active and passive control approaches. The active approach employed is the actively controlled partial span trailing edge flaps (ACF), implemented in single and dual, servo and plain flap configurations. The passive approach is based on varying the sweep and anhedral on the tip of the rotor. Two different modern helicopters are chosen as the baseline for the implementation of ACF approach, one resembling a four-bladed MBB BO-105 hingeless rotor and the other similar to a five-bladed MD-900 bearingless rotor. The structural model is based on a finite element approach capable of simulating composite helicopter blades with swept tips, and representing multiple load paths at the blade root which is a characteristic of bearingless rotors. An unsteady compressible aerodynamic model based on a rational function approximation (RFA) approach is combined with a free wake analysis which has been enhanced by improving the wake analysis resolution and modeling a dual vortex structure. These enhancements are important for capturing BVI effects. A method for predicting compressible unsteady blade surface pressure distribution on rotor blades has been developed, which is required by the acoustic analysis. A modified version of helicopter noise code WOPWOP with provisions for blade flexibility has been combined with the aeroelastic analysis to predict the BVI noise. Several variants of the higher harmonic control (HHC) algorithm have been applied for the active noise control, as well as the simultaneous vibration and noise control. Active control of BVI noise is accomplished using feedback from an onboard microphone. The simulation has been extensively validated against experimental data and

  16. Aeroacoustic control of landing gear noise using perforated fairings

    Boorsma, Koen


    A study was performed to investigate and optimize the application of perforated fairings for landing gear noise control. The sparse knowledge about this new subject has necessitated a more fundamental study involving a basic fairing-strut configuration, followed by wind tunnel tests on a simplified landing gear configuration incorporating perforated fairings. For the basic configuration, various exchangeable perforated half-cylindrical shells shrouding a circular cylinder we...

  17. Diffusion of Active Particles Subject both to Additive and Multiplicative Noises

    WANG Shao-Hua; YANG Ming; WU Da-Jin


    We consider a Langevin equation of active Brownian motion which contains a multiplicative as well as an additive noise term.We study the dependences of the effective diffusion coefficient Deff on both the additive and multiplicative noises.It is found that for fixed small additive noise intensity Deff varies non-monotonously with multiplicative noise intensity, with a minimum at a moderate value of multiplicative noise, and Deff increases monotonously, however, with the multiplicative noise intensity for relatively strong additive noise; for fixed multiplicative noise intensity Deff decreases with growing additive noise intensity until it approaches a constant.An explanation is also given of the different behavior of Deff as additive and multiplicative noises approach infinity,respectively.%@@ We consider a Langevin equation of active Brownian motion which contains a multiplicative as well as an additive noise term.We study the dependences of the effective diffusion coefficient Deff on both the additive and multiplicative noises.It is found that for fixed small additive noise intensity Deff varies non-monotonously with multiplicative noise intensity, with a minimum at a moderate value of multiplicative noise, and Deff increases monotonously, however, with the multiplicative noise intensity for relatively strong additive noise; for fixed multiplicative noise intensity Deff decreases with growing additive noise intensity until it approaches a constant.An explanation is also given of the different behavior of Deff as additive and multiplicative noises approach infinity, respectively.

  18. Scope for active noise abatement in vehicle diesel engines

    Summerauer, I.; Boesch, N.


    Noise reduction measures must be directed to the engine, the exhaust system, and the cooling system (fan) all of which contribute approximately 90% of the sound energy emitted from commercial diesel trucks. The noise generation processes were visualized and limiting conditions fixed by law were considered in establishing criteria for active solar noise abatement measures. A more effective silencer and better vibration damping on the surface of the silencer and exhaust pipes can reduce noise from the exhaust system. Acoustic emission generated by the fan and air flow can be reduced by decreasing flow velocity or by turning on the fan only when a full cooling output is required (10% of the time). Active measures are needed on the engine itself either at the point of the solid-borne sound transmission or at the point of the solid-borne vibrations. The predominant effect is on the engine casing; oil sump; air suction pipe or air charge line; the flywheel casing; and the clutch housing.

  19. Advance Noise Control Fan II: Test Rig Fan Risk Management Study

    Lucero, John


    Since 1995 the Advanced Noise Control Fan (ANCF) has significantly contributed to the advancement of the understanding of the physics of fan tonal noise generation. The 9'x15' WT has successfully tested multiple high speed fan designs over the last several decades. This advanced several tone noise reduction concepts to higher TRL and the validation of fan tone noise prediction codes.

  20. Noise influence on spike activation in a Hindmarsh–Rose small-world neural network

    Zhe, Sun; Micheletto, Ruggero


    We studied the role of noise in neural networks, especially focusing on its relation to the propagation of spike activity in a small sized system. We set up a source of information using a single neuron that is constantly spiking. This element called initiator x o feeds spikes to the rest of the network that is initially quiescent and subsequently reacts with vigorous spiking after a transitional period of time. We found that noise quickly suppresses the initiator’s influence and favors spontaneous spike activity and, using a decibel representation of noise intensity, we established a linear relationship between noise amplitude and the interval from the initiator’s first spike and the rest of the network activation. We studied the same process with networks of different sizes (number of neurons) and found that the initiator x o has a measurable influence on small networks, but as the network grows in size, spontaneous spiking emerges disrupting its effects on networks of more than about N = 100 neurons. This suggests that the mechanism of internal noise generation allows information transmission within a small neural neighborhood, but decays for bigger network domains. We also analyzed the Fourier spectrum of the whole network membrane potential and verified that noise provokes the reduction of main θ and α peaks before transitioning into chaotic spiking. However, network size does not reproduce a similar phenomena; instead we recorded a reduction in peaks’ amplitude, a better sharpness and definition of Fourier peaks, but not the evident degeneration to chaos observed with increasing external noise. This work aims to contribute to the understanding of the fundamental mechanisms of propagation of spontaneous spiking in neural networks and gives a quantitative assessment of how noise can be used to control and modulate this phenomenon in Hindmarsh‑Rose (H‑R) neural networks.

  1. Performance of PRD Welled Surfaces in T Shape Noise Barriers for Controlling Environmental Noise

    S Momen Bellah


    Full Text Available "n "n "nBackgrounds and Objectives: There is a considerable notice in the use of noise barriers in recent years. Noise barriers as a control noise solution can increase the insertion loss to protect receivers. This paper presents the results of an investigation about the acoustic efficiency of primitive root sequence diffuser (PRD on environmental single T-shape barrier."nMaterials and Methods: A 2D boundary element method (BEM is used to predict the insertion loss of the tested barriers. The results of rigid and with quadratic residue diffuser (QRD coverage are also predicted for comparison."nResults: It is found that decreasing the design frequency of PRD shifts the frequency effects towards lower frequencies, and therefore the overall A-weighted insertion loss is improved. It is also found that using wire mesh with reasonably efficient resistivity on the top surface of PRD improves the efficiency of the reactive barriers; however utilizing wire meshes with flow resistivity higher than specific acoustic impedance of air on the PRD top of a diffuser barrier significantly reduces the performance of the barrier within the frequency bandwidth of the diffuser. The performance of PRD covered T-shape barrier at 200 Hz was found to be higher than that of its equivalent QRD barriers in both the far field and areas close to the ground. The amount of improvement compared made by PRD barrier compared with its equivalent rigid barrier at far field is about 2 to 3 dB, while this improvement relative to barrier model .QR4. can reach up to 4- 6 dB."nConclusion: Employing PRD on the top surface of T-shape barrier is found to improve the performance of barriers compared with using rigid and QRD coverage at the examined receiver locations.

  2. Active noise compensation for multichannel magnetocardiography in an unshielded environment

    Aarnink, W.A.M.; Bosch, van den, G.; Roelofs, T.-M.; Verbiesen, M.; Holland, H.J.; Brake, ter, H.J.M.; Rogalla, H.


    A multichannel high-T/sub c/-SQUID-based heart scanner for unshielded environments is under development, Outside a magnetically shielded room, sensitive SQUID measurements are possible using gradiometers. However, it is difficult to realize large-baseline gradiometers in high-T/sub c/ materials, Therefore, the authors developed two active noise compensation techniques. In the Total Field Compensation technique, a Helmholtz type coil set is placed around the sensors. One magnetometer is used a...

  3. Control of noise and structural vibration a MATLAB-based approach

    Mao, Qibo


    Control of Noise and Structural Vibration presents a MATLAB®-based approach to solving the problems of undesirable noise generation and transmission by structures and of undesirable vibration within structures in response to environmental or operational forces. The fundamentals of acoustics, vibration and coupling between vibrating structures and the sound fields they generate are introduced including a discussion of the finite element method for vibration analysis. Following this, the treatment of sound and vibration control begins, illustrated by example systems such as beams, plates and double plate structures. Sensor and actuator placement is explained as is the idea of modal sensor–actuators. The design of appropriate feedback systems includes consideration of basic stability criteria and robust active structural acoustic control. Single and multi-mode positive position feedback (PPF) control systems are also described in the context of loudspeaker–duct model with non-collocated loudspeaker–microp...

  4. Analysis of noise characteristics for the active pixels in CMOS image sensors for X-ray imaging

    Kim, Young Soo; Cho, Gyuseong; Bae, Jun-Hyung


    CMOS image sensors have poorer performance compared to conventional charge coupled devices (CCDs). Since CMOS Active Pixel Sensors (APSs) in general have higher temporal noise, higher dark current, smaller full well charge capacitance, and lower spectral response, they cannot provide the same wide dynamic range and superior signal to noise ratio as CCDs. In view of electronic noise, the main source for the CMOS APS is the pixel, along with other signal processing blocks such as row and column decoder, analog signal processor (ASP), analog-to-digital converter (ADC), and timing and control logic circuitry. Therefore, it is important and necessary to characterize noise of the active pixels in CMOS APSs, and we performed experimental measurements and comparisons with theoretical estimations. To derive noise source of the pixels, we designed and fabricated four types of CMOS active pixels, and each pixel is composed of a photodiode and three MOS transistors. The size of these pixels is 100 μm×100 μm. The test chip was fabricated using ETRI 0.8 μm (2P/2M) standard CMOS process. It was found that the dominant noise in CMOS active pixels is shot noise during integration under normal operating conditions. And, it was also seen that epitaxial type pixels have similar noise level compared to non-epitaxial type, and the noise of diffusion type pixel is larger than for a well type pixel on the same substrate type.

  5. Analysis of noise characteristics for the active pixels in CMOS image sensors for X-ray imaging

    CMOS image sensors have poorer performance compared to conventional charge coupled devices (CCDs). Since CMOS Active Pixel Sensors (APSs) in general have higher temporal noise, higher dark current, smaller full well charge capacitance, and lower spectral response, they cannot provide the same wide dynamic range and superior signal to noise ratio as CCDs. In view of electronic noise, the main source for the CMOS APS is the pixel, along with other signal processing blocks such as row and column decoder, analog signal processor (ASP), analog-to-digital converter (ADC), and timing and control logic circuitry. Therefore, it is important and necessary to characterize noise of the active pixels in CMOS APSs, and we performed experimental measurements and comparisons with theoretical estimations. To derive noise source of the pixels, we designed and fabricated four types of CMOS active pixels, and each pixel is composed of a photodiode and three MOS transistors. The size of these pixels is 100 μmx100 μm. The test chip was fabricated using ETRI 0.8 μm (2P/2M) standard CMOS process. It was found that the dominant noise in CMOS active pixels is shot noise during integration under normal operating conditions. And, it was also seen that epitaxial type pixels have similar noise level compared to non-epitaxial type, and the noise of diffusion type pixel is larger than for a well type pixel on the same substrate type

  6. Comparison of various decentralised structural and cavity feedback control strategies for transmitted noise reduction through a double panel structure

    Ho, Jen-Hsuan; Berkhoff, Arthur


    This paper compares various decentralised control strategies, including structural and acoustic actuator-sensor configuration designs, to reduce noise transmission through a double panel structure. The comparison is based on identical control stability indexes. The double panel structure consists of two panels with air in between and offers the advantages of low sound transmission at high frequencies, low heat transmission, and low weight. The double panel structure is widely used, such as in the aerospace and automotive industries. Nevertheless, the resonance of the cavity and the poor sound transmission loss at low frequencies limit the double panel's noise control performance. Applying active structural acoustic control to the panels or active noise control to the cavity has been discussed in many papers. In this paper, the resonances of the panels and the cavity are considered simultaneously to further reduce the transmitted noise through an existing double panel structure. A structural-acoustic coupled model is developed to investigate and compare various structural control and cavity control methods. Numerical analysis and real-time control results show that structural control should be applied to both panels. Three types of cavity control sources are presented and compared. The results indicate that the largest noise reduction is obtained with cavity control by loudspeakers modified to operate as incident pressure sources.

  7. Noise-controlled bistability in an excitable system with positive feedback

    Kromer, Justus A.; Pinto, Reynaldo D.; Lindner, Benjamin; Schimansky-Geier, Lutz


    We study the interplay between noise and a positive feedback mechanism in an excitable system that generates events. We show that such a system can exhibit a bistability in the dynamics of the event generation (states of low and high activity). The stability of the two states is determined by the strength of the noise such that a change of noise intensity permits complete control over the probabilities with which the two states are occupied. The bistability also has strong implications for the regularity of the event generation. While the irregularity of the interevent interval (short-time variability) and the asymptotic Fano factor of the event count (long-time variability) are limited if the system is only in one of the two states, we show that both measures of variability display giant values if both states are equally likely. The long-time variability is additionally amplified by long-range positive correlations of the interevent intervals.

  8. The effect of human activity noise on the acoustic quality in open plan office

    Dehlbæk, Tania Stenholt; Jeong, Cheol-Ho; Brunskog, Jonas;


    A disadvantage of open plan offices is the noise annoyance. Noise problems in open plan offices have been dealt with in several studies, and standards have been set up. Still, what has not been taken into account is the effect of human activity noise on acoustic conditions. In this study......, measurements of the general office noise levels and the room acoustic conditions according to ISO 3382-3 have been carried out in five open plan offices. Probability density functions of the sound pressure level have been obtained, and the human activity noise has been identified. Results showed a decrease in...... D2,S have an impact on the variation in the activity noise. At 1 kHz, the technical background noise influences human activity noise positively. In both octave bands, the human activity noise level varies significantly with the office type, from a call center to a lawyer’s office....

  9. Cooperating or Fighting with Control Noise in the Optimal Manipulation of Quantum Dynamics

    Shuang, F; Shuang, Feng; Rabitz, Herschel


    This paper investigates the impact of control field noise on the optimal manipulation of quantum dynamics. Simulations are performed on several multilevel quantum systems with the goal of population transfer in the presence of significant control noise. The noise enters as run-to-run variations in the control amplitude and phase with the observation being an ensemble average over many runs as is commonly done in the laboratory. A genetic algorithm with an improved elitism operator is used to find the optimal field that either fights against or cooperates with control field noise. When seeking a high control yield it is possible to find fields that successfully fight with the noise while attaining good quality stable results. When seeking modest control yields, fields can be found which are optimally shaped to cooperate with the noise and thereby drive the dynamics more efficiently. In general, noise reduces the coherence of the dynamics, but the results indicate that population transfer objectives can be met ...

  10. Amplitude noise in passively and actively operated masers

    A calculation of the power spectral density of amplitude fluctuations in masers is presented, which gives results in close agreement with others. The maximum of this power spectral density, which appears in specified conditions, for a Fourier frequency related to the Rabi frequency of atoms is observed for the first time both in a hydrogen and a rubidium maser. The given model is completed to include a coherent excitation, as required in passively operated masers. Two methods for the interrogation of the atoms are considered. In the first one, the maximum of the atomic emission line is probed and in the second one, the null of the atomic dispersion line is observed. The power spectral density of fractional frequency fluctuations of the slaved frequency generator is calculated in both cases, including the effect of thermal noise in the microwave cavity and of noise added by the microwave receiver. Optimum operating conditions are specified. The cavity pulling factor is specified for both methods of interrogation and the effect of noise in the control of the microwave cavity resonant frequency is considered. Finally a useful design criterion is given for passively operated masers

  11. Noise Reduction in Double‐Panel Structures by Cavity and Panel Resonance Control

    Ho, Jen-Hsuan; Berkhoff, Arthur


    This paper presents an investigation of the cavity and the panel resonance control in a double‐panel structure. The double‐panel structure, which consists of two panels with air in the gap, is widely adopted in many applications such as aerospace due to its light weight and effective transmission‐loss at high frequency. However, the resonance of the cavity and the poor transmission‐loss at low frequency limit its noise control performance. Applying active control forces on the panels or utili...

  12. Distinct noise-controlling roles of multiple negative feedback mechanisms in a prokaryotic operon system.

    Nguyen, L K; Kulasiri, D


    Molecular fluctuations are known to affect dynamics of cellular systems in important ways. Studies aimed at understanding how molecular systems of certain regulatory architectures control noise therefore become essential. The interplay between feedback regulation and noise has been previously explored for cellular networks governed by a single negative feedback loop. However, similar issues within networks consisting of more complex regulatory structures remain elusive. The authors investigate how negative feedback loops manage noise within a biochemical cascade concurrently governed by multiple negative feedback loops, using the prokaryotic tryptophan (trp) operon system in Escherechia coli as the model system. To the authors knowledge, this is the first study of noise in the trp operon system. They show that the loops in the trp operon system possess distinct, even opposing, noise-controlling effects despite their seemingly analogous feedback structures. The enzyme inhibition loop, although controlling the last reaction of the cascade, was found to suppress noise not only for the tryptophan output but also for other upstream components. In contrast, the Repression (Rep) loop enhances noise for all systems components. Attenuation (Att) poses intermediate effects by attenuating noise for the upstream components but promoting noise for components downstream of its target. Regarding noise at the output tryptophan, Rep and Att can be categorised as noise-enhancing loops whereas Enzyme Inhibition as a noise-reducing loop. These findings suggest novel implications in how cellular systems with multiple feedback mechanisms control noise. [Includes supplementary material]. PMID:21405203


    Nikolic, Aleksandar; Nikolic, Emilija


    Environmental and occupational noise is common nuisance that affects the health of employees. Performed health checks of employees engaged by Company “Pomorski Saobraćaj” showed that 5% of examined sailors had hearing loss. The results were a trigger for starting experiment on noise risk assessment with objective to discover possibilities of noise pollution presence, precise significant noise sources and describe solutions for eliminating negative effects. Several measurements on five posi...

  14. Active Vibration Control of Axial Piston Machine using Higher Harmonic Least Mean Square Control of Swash Plate

    Kim, Taeho; Ivantysynova, Monika


    Noise emission is a major drawback of the positive displacement machine. The noise source can be divided into structure borne noise source (SBNS) and fluid borne noise source (FBNS). Passive techniques such as valve plate optimization have been used for noise reduction of axial piston machines. However, passive techniques are only effective for limited operating conditions or at least need compromises in design. In this paper, active vibration control of swash plate is investigated for vibrat...

  15. Optimizing noise control strategy in a forging workshop.

    Razavi, Hamideh; Ramazanifar, Ehsan; Bagherzadeh, Jalal


    In this paper, a computer program based on a genetic algorithm is developed to find an economic solution for noise control in a forging workshop. Initially, input data, including characteristics of sound sources, human exposure, abatement techniques, and production plans are inserted into the model. Using sound pressure levels at working locations, the operators who are at higher risk are identified and picked out for the next step. The program is devised in MATLAB such that the parameters can be easily defined and changed for comparison. The final results are structured into 4 sections that specify an appropriate abatement method for each operator and machine, minimum allowance time for high-risk operators, required damping material for enclosures, and minimum total cost of these treatments. The validity of input data in addition to proper settings in the optimization model ensures the final solution is practical and economically reasonable. PMID:24934422

  16. The Effect of Non-Harmonic Active Twist Actuation on BVI Noise

    Fogarty, David E.; Wilbur, Matthew L.; Sekula, Martin K.


    The results of a computational study examining the effects of non-harmonic active-twist control on blade-vortex interaction (BVI) noise for the Apache Active Twist Rotor are presented. Rotor aeroelastic behavior was modeled using the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics code and the rotor noise was predicted using the acoustics code PSU-WOPWOP. The application of non-harmonic active-twist inputs to the main rotor blade system comprised three parameters: azimuthal location to start actuation, azimuthal duration of actuation, and magnitude of actuation. The acoustic analysis was conducted for a single low-speed flight condition of advance ratio mu=0.14 and shaft angle-of-attack, a(sub s)=+6deg. BVI noise levels were predicted on a flat plane of observers located 1.1 rotor diameters beneath the rotor. The results indicate significant reductions of up to 10dB in BVI noise using a starting azimuthal location for actuation of 90?, an azimuthal duration of actuation of 90deg, and an actuation magnitude of +1.5 ft-lb.

  17. Optimal control of a linear system with multiplicative noise at control parameter

    Smirnov, I. P.


    We investigate a control process described by a linear system of ordinary differential equations with a noise of special type acting to the control parameter. As the cost functional the probability of the final state vector to enter to a given set in the phase space is considered. Necessary conditions of optimality (of the Pontryagin maximum principle form) and existence theorems are developed. The initial control problem was trasformed to an auxiliary deterministic problem, the differentiabi...

  18. Subjective annoyance caused by indoor low-level and low frequency noise and control method

    DI Guo-qing; ZHANG Bang-jun; SHANG Qi


    The influence of low-level noise has not been widely noticed. This paper discovered that low-level and low frequency noise(Aweighted equivalent level Leq < 45 dB) causes higher probability of subjective annoyance. The fuzzy mathematic principle was applied to deal with the threshold level of subjective annoyance from noise in this study; there is preferable relationship between the indoor noise and noise annoyance at low frequency noise level. Study indicated at the same centered noise level, the change of annoyance probability is mainly caused by the change of the frequency spectrum characteristic of the indoor noise. Under low noise level environment, without change of the medium-low frequency noise, the slight increase of medium-high frequency noise level with the help of noise sheltering effect can significantly reduce the noise annoyance. This discovery brings a new resolution on how to improve the environmental quality of working or living places. A noise control model is given in this study according to the acoustic analysis.

  19. Three-Party Controlled Quantum Teleportation with Six-Photon Entangled States via Collective Noise Channel

    Two three-party controlled quantum teleportation protocols using six-photon entangled states are proposed for circumventing collective noise. It can be performed in collective-dephasing noise or collective-rotation noise with unitary successful probability. Due to the symmetry of the quantum channel, each participant can act as a sender, a receiver or a controller. Moreover, it can be generalized to multiparty controlled teleportation protocols. (authors)

  20. What kind of noise is brain noise? Anomalous scaling behavior of the resting brain activity fluctuations.

    Daniel eFraiman


    Full Text Available The study of spontaneous fluctuations of brain activity, often referred as brain noise, is getting increasing attention in functional magnetic resonance imaging (fMRI studies. Despite important efforts, much of the statistical properties of such fluctuations remain largely unknown. This work scrutinize these fluctuations looking at specific statistical properties which are relevant to clarify its dynamical origins. Here, three statistical features which clearly differentiate brain data from naive expectations for random processes are uncovered: First, the variance of the fMRI mean signal as a function of the number of averaged voxels remains constant across a wide range of observed clusters sizes. Second, the anomalous behavior of the variance is originated by bursts of synchronized activity across regions, regardless of their widely different sizes. Finally, the correlation length (i.e., the length at which the correlation strength between two regions vanishes as well as mutual information diverges with the cluster's size considered, such that arbitrarily large clusters exhibit the same collective dynamics than smaller ones. These three properties are known to be exclusive of complex systems exhibiting critical dynamics, where the spatio-temporal dynamics show these peculiar type of fluctuations. Thus, these findings are fully consistent with previous reports of brain critical dynamics, and are relevant for the interpretation of the role of fluctuations and variability in brain function in health and disease.

  1. Acoustic noise radiated by PWM-controlled induction machine drives

    Lo, W.C.; Chan, C.C.; Zhu, Z Q; Xu, L.; Howe, D.; Chau, K. T.


    This paper investigates the acoustic noise radiated from two nominally identical induction motors when fed from sinusoidal, and asymmetric regular sampling subharmonic and space-vector pulsewidth modulation (PWM) converters. The theory for analyzing the noise spectrum is developed further to account for the interaction between the motor and the drive. It is shown that manufacturing tolerances can result in significant differences in the noise level emitted from nominally identical motors, and...

  2. A noise control package for vibrating screens1),2)

    Lowe, M. Jenae; Yantek, David S.; Yang, Junyi; Schuster, Kevin C.; Mechling, Jessie J.


    Hearing loss was the second-most common illness reported to the Mine Safety and Health Administration (MSHA) in 2009. Furthermore, between 2000 and 2010, 30% of all noise-related injury complaints reported to MSHA were for coal preparation plant employees. Previous National Institute for Occupational Safety and Health (NIOSH) studies have shown that vibrating screens are key noise sources to address in order to reduce coal preparation plant noise. In response, NIOSH researchers have developed...

  3. Noise Control And Speech Intelligibility Improvement Of A Toll Plaza

    Mongeau, Luc; Bernhard, Robert J.; Feist, Jeffery P.


    Vehicular toll roads are one component of many municipal transportation systems. Open communication windows, often used in tollbooths, facilitate essential communication and monetary transactions. However, the vehicle noise generated outside the booth is easily transmitted into the booth via the open window. Personnel working at toll collection plazas are exposed to extended, continuous traffic noise. Sustained noise levels of this nature may cause hearing loss, induce fatigue or stress, and ...

  4. 'NASA Invention of the Year' Controls Noise and Vibration


    Developed at NASA's Langley Research Center, the Macro-Fiber Composite (MFC) is designed to control vibration, noise, and deflections in composite structural beams and panels. Smart Material Corporation specializes in the development of piezocomposite components, and licensed the MFC technology from Langley in 2002. To date, Smart Material Corporation has sold MFCs to over 120 customers, including such industry giants as Volkswagen, Toyota, Honda, BMW, General Electric, and the tennis company, HEAD. The company estimates that its customers have filed at least 100 patents for their various unique uses of the technology. In addition, the company's product portfolio has grown to include piezoceramic fibers and fiber composites, piezoceramic actuators and sensors, and test equipment for these products. It also offers a compact, lightweight power system for MFC testing and validation. Consumer applications already on the market include piezoelectric systems as part of audio speakers, phonograph cartridges and microphones, and recreational products requiring vibration control, such as skis, snowboards, baseball bats, hockey sticks, and tennis racquets.

  5. Improper activation of D1 and D2 receptors leads to excess noise in prefrontal cortex

    Michael eAvery


    Full Text Available The dopaminergic system has been shown to control the amount of noise in the prefrontal cortex (PFC and likely plays an important role in working memory and the pathophysiology of schizophrenia. We developed a model that takes into account the known receptor distributions of D1 and D2 receptors, the changes these receptors have on neuron response properties, as well as identified circuitry involved in working memory. Our model suggests that D1 receptor under-stimulation in supragranular layers gates internal noise into the PFC leading to cognitive symptoms as has been proposed in attention disorders, while D2 over-stimulation gates noise into the PFC by over-activation of cortico-striatal projecting neurons in infragranular layers. We apply this model in the context of a memory-guided saccade paradigm and show deficits similar to those observed in schizophrenic patients. We also show set-shifting impairments similar to those observed in rodents with D1 and D2 receptor manipulations. We discuss how the introduction of noise through changes in D1 and D2 receptor activation may account for many of the symptoms of schizophrenia depending on where this dysfunction occurs in the PFC.

  6. Active noise canceling system for mechanically cooled germanium radiation detectors

    Nelson, Karl Einar; Burks, Morgan T


    A microphonics noise cancellation system and method for improving the energy resolution for mechanically cooled high-purity Germanium (HPGe) detector systems. A classical adaptive noise canceling digital processing system using an adaptive predictor is used in an MCA to attenuate the microphonics noise source making the system more deployable.

  7. Automotive applications of rapid prototyping for active vibration control

    Bohn, C.; Svaricek, F. [Continental Gummi-Werke AG, Hannover (Germany); Karkosch, H.J.; Marienfeld, P.M. [ContiTech Vibration Control GmbH, Hannover (Germany)


    This paper presents some recent results of Continental's research and development activities in the area of active vibration control. First, a brief overview of different approaches to active noise and vibration control is given. This is followed by a discussion of the rapid controller prototyping process that is currently being introduced. Finally, some experimental results obtained in cooperation with an automobile manufacturer are presented. These results demonstrate that major noise and vibration attenuation can be achieved through active vibration control in automobiles. (orig.)

  8. Noise focusing and the emergence of coherent activity in neuronal cultures

    Orlandi, Javier G.; Soriano, Jordi; Alvarez-Lacalle, Enrique; Teller, Sara; Casademunt, Jaume


    At early stages of development, neuronal cultures in vitro spontaneously reach a coherent state of collective firing in a pattern of nearly periodic global bursts. Although understanding the spontaneous activity of neuronal networks is of chief importance in neuroscience, the origin and nature of that pulsation has remained elusive. By combining high-resolution calcium imaging with modelling in silico, we show that this behaviour is controlled by the propagation of waves that nucleate randomly in a set of points that is specific to each culture and is selected by a non-trivial interplay between dynamics and topology. The phenomenon is explained by the noise focusing effect--a strong spatio-temporal localization of the noise dynamics that originates in the complex structure of avalanches of spontaneous activity. Results are relevant to neuronal tissues and to complex networks with integrate-and-fire dynamics and metric correlations, for instance, in rumour spreading on social networks.

  9. Active control of transmitted sound in buildings

    Thompsett, Russell Harvey George

    The problem of noise from neighbours has increased dramatically over the last few years. Many of the noise complaints are due to the high level, low frequency noise from modern stereo equipment, and are often described in terms of the low frequency characteristics of the music; the repetitive, booming, bass beat. The objective of this research was to establish the feasibility of applying active noise control to alleviate this problem. The initial approach was to evaluate the possibility of exploiting the dominance of individual modes in the response of rooms at low frequency to effect global control. However, initial investigations using a modal model of the sound field revealed that this would be difficult due to the contribution of many acoustic modes excited off resonance. This conclusion was supported by measurements of acoustic room responses in typical buildings, illustrating a non-resonant characteristic. Consequently, attention was turned to the feasibility of using local active control systems to create zones of quiet by concentrating control at a specific location near the observers ears, for example in a seat headrest, or near the pillows of a bed. The lack of a reference signal in either approach requires the use of a feedback control strategy. With a typically non-resonant system, the predictability in the disturbance necessary for successful feedback control must be contained in the primary excitation, namely the music. Examples of different music styles were investigated and of those with the potential to be a nuisance surprisingly few were significantly more predictable than a random disturbance. As expected the most encouraging control performance simulations were found for modern dance music, with a strong repetitive beat. A real-time, local controller was demonstrated in the laboratory with such a disturbance signal and the properties of the quiet zone were measured. The subjective response when hearing the controller in operation was found to be

  10. Updating working memory in aircraft noise and speech noise causes different fMRI activations

    Sætrevik, Bjørn; Sörqvist, Patrik


    The present study used fMRI/BOLD neuroimaging to investigate how visual-verbal working memory is updated when exposed to three different background-noise conditions: speech noise, aircraft noise and silence. The number-updating task that was used can distinguish between “substitution processes,” which involve adding new items to the working memory representation and suppressing old items, and “exclusion processes,” which involve rejecting new items and maintaining an intact memory set. The cu...

  11. Industrial Noise Pollution and the Need for Applying Protocols for its Control and Decrease

    Parvin Nasiri


    Full Text Available Industrialization has had many complications for human beings and has been a threat to social mental and physical health. Vibration induced noises in the workplace is one of the main devastating factor in producing hearing loss in workers. Recently, several investigations on the issue of noise pollution and noise dosimetry and also Noise induced hearing loss have been developed. In the current article we will have a look and sometimes reconsideration on the results and of these studies and will discuss the findings in regard to noise control and management in details.

  12. Dopamine Activation Preserves Visual Motion Perception Despite Noise Interference of Human V5/MT

    Yousif, Nada; Fu, Richard Z.; Abou-El-Ela Bourquin, Bilal; Bhrugubanda, Vamsee; Schultz, Simon R.


    When processing sensory signals, the brain must account for noise, both noise in the stimulus and that arising from within its own neuronal circuitry. Dopamine receptor activation is known to enhance both visual cortical signal-to-noise-ratio (SNR) and visual perceptual performance; however, it is unknown whether these two dopamine-mediated phenomena are linked. To assess this, we used single-pulse transcranial magnetic stimulation (TMS) applied to visual cortical area V5/MT to reduce the SNR focally and thus disrupt visual motion discrimination performance to visual targets located in the same retinotopic space. The hypothesis that dopamine receptor activation enhances perceptual performance by improving cortical SNR predicts that dopamine activation should antagonize TMS disruption of visual perception. We assessed this hypothesis via a double-blinded, placebo-controlled study with the dopamine receptor agonists cabergoline (a D2 agonist) and pergolide (a D1/D2 agonist) administered in separate sessions (separated by 2 weeks) in 12 healthy volunteers in a William's balance-order design. TMS degraded visual motion perception when the evoked phosphene and the visual stimulus overlapped in time and space in the placebo and cabergoline conditions, but not in the pergolide condition. This suggests that dopamine D1 or combined D1 and D2 receptor activation enhances cortical SNR to boost perceptual performance. That local visual cortical excitability was unchanged across drug conditions suggests the involvement of long-range intracortical interactions in this D1 effect. Because increased internal noise (and thus lower SNR) can impair visual perceptual learning, improving visual cortical SNR via D1/D2 agonist therapy may be useful in boosting rehabilitation programs involving visual perceptual training. SIGNIFICANCE STATEMENT In this study, we address the issue of whether dopamine activation improves visual perception despite increasing sensory noise in the visual cortex

  13. FIACH: A biophysical model for automatic retrospective noise control in fMRI.

    Tierney, Tim M; Weiss-Croft, Louise J; Centeno, Maria; Shamshiri, Elhum A; Perani, Suejen; Baldeweg, Torsten; Clark, Christopher A; Carmichael, David W


    Different noise sources in fMRI acquisition can lead to spurious false positives and reduced sensitivity. We have developed a biophysically-based model (named FIACH: Functional Image Artefact Correction Heuristic) which extends current retrospective noise control methods in fMRI. FIACH can be applied to both General Linear Model (GLM) and resting state functional connectivity MRI (rs-fcMRI) studies. FIACH is a two-step procedure involving the identification and correction of non-physiological large amplitude temporal signal changes and spatial regions of high temporal instability. We have demonstrated its efficacy in a sample of 42 healthy children while performing language tasks that include overt speech with known activations. We demonstrate large improvements in sensitivity when FIACH is compared with current methods of retrospective correction. FIACH reduces the confounding effects of noise and increases the study's power by explaining significant variance that is not contained within the commonly used motion parameters. The method is particularly useful in detecting activations in inferior temporal regions which have proven problematic for fMRI. We have shown greater reproducibility and robustness of fMRI responses using FIACH in the context of task induced motion. In a clinical setting this will translate to increasing the reliability and sensitivity of fMRI used for the identification of language lateralisation and eloquent cortex. FIACH can benefit studies of cognitive development in young children, patient populations and older adults. PMID:26416652

  14. Noise Temperature Characteristics and Gain-control of Avalanche Photodiodes for Laser Radar

    CAI Xi-ping; SHANG Hong-Bo; BAI Ji-yuan; YANG Shuang; WANG Li-na


    Avalanche photodiodes(APDs) are promising light sensors with high quantum efficiency and low noise. It has been extensively used in radiation detection, laser radar and other weak signal detection fields. Unlike other photodiodes, APD is a very sensitive light detector with very high internal gain. The basic theory shows that the gain of APD is related to the temperature. The internal gain fluctuates with the variation of temperature. Investigated was the influence of the variation of the gain induced by the fluctuation of temperature on the output from APD for a very weak laser pulse input in laser radar. An active reverse-biased voltage compensation method is used to stabilize the gain of APD. An APD model is setup to simulate the detection of light pulse signal. The avalanche process, various noises and temperature's effect are all included in the model. Our results show that for the detection of weak light signal such as in laser radar, even a very small fluctuation of temperature could cause a great effect on APD's gain. The results show that the signal-to-noise ratio of the APD's output could be improved effectively with the active gain-control system.

  15. Inertia Wheel on Low-Noise Active Magnetic Suspension

    Carabelli, S.; Genta, G.; Silvagni, M.; Tonoli, A.


    Magnetic bearings are particularly suited for space applications for a number of reasons: - they are ideally suited for vacuum applications; - the lack of lubrication and wear enhances the reliability and guaranties a long maintenance-free operation - the low drag torque decreases power consumption and reduces the torque exerted on the stator of the machine. - the possibility of insulating actively the spacecraft from the excitation due to unbalance of the rotating system In the case of reaction wheels, a well designed magnetic suspension allows high speed operation with a very low power consumption and vibration level. Conversely, microgravity (and possibly vacuum) operation is an advantage for magnetic bearings. The absence of static forces allows to operate with low current levels, thus reducing electrical noise and allowing to reach even lower vibration levels than in Earth applications of magnetic bearings. Active magnetic bearings (AMB) allow to adapt the working characteristics of the system to the operating needs: it is possible to use the actuators to lock the system during launch (absence of grabbers) and to stiffen the suspension when the spacecraft is accelerated (impulsive phases), while working in conditions optimised for microgravity when this is needed. Magnetic suspension systems designed for microgravity environment cannot be correctly tested on the ground. Testing in ground conditions results in the need of grossly overdesigning the levitation device; furthermore, in some cases ground testing is completely impossible, if not by introducing devices which compensate for the Earth gravitational field. If the compensation for the gravitational force is supplied by the same actuators used for microgravity operation, the actuators and the power amplifiers must be overdesigned and in some cases the suspension can be altogether impossible. They work in conditions which are much different from nominal ones and, above all, it is impossible to reach the

  16. Improving postural control by applying mechanical noise to ankle muscle tendons.

    Borel, Liliane; Ribot-Ciscar, Edith


    The application of subthreshold mechanical vibrations with random frequencies (white mechanical noise) to ankle muscle tendons is known to increase muscle proprioceptive information and to improve the detection of ankle movements. The aim of the present study was to analyze the effect of this mechanical noise on postural control, its possible modulation according to the sensory strategies used for postural control, and the consequences of increasing postural difficulty. The upright stance of 20 healthy young participants tested with their eyes closed was analyzed during the application of four different levels of noise and compared to that in the absence of noise (control) in three conditions: static, static on foam, and dynamic (sinusoidal translation). The quiet standing condition was conducted with the eyes open and closed to determine the subjects' visual dependency to maintain postural stability. Postural performance was assessed using posturographic and motion analysis evaluations. The results in the static condition showed that the spectral power density of body sway significantly decreased with an optimal level of noise and that the higher the spectral power density without noise, the greater the noise effect, irrespective of visual dependency. Finally, noise application was ineffective in the foam and dynamic conditions. We conclude that the application of mechanical noise to ankle muscle tendons is a means to improve quiet standing only. These results suggest that mechanical noise stimulation may be more effective in more impaired populations. PMID:27021075

  17. Control of linear accelerator noise in the Los Alamos free-electron laser (FEL)

    The Los Alamos FEL requires tight control of the amplitudes and phases of the fields in two linear accelerator tanks to obtain stable lasing. The accelerator control loops must establish constant, stable, repeatable amplitudes and phases of the rf fields and must have excellent bandwidth to control high-frequency noise components. A model of the feedback loops has been developed that agrees well with measurements and allows easy substitution of components and circuits, thus reducing breadboarding requirements. The model permits both frequency and time-domain analysis. This paper describes the accelerator control scheme and our model and discusses the control of noise in feedback loops, showing how low-frequency-noise components (errors) can be corrected, but high-frequency-noise components (errors) are actually amplified by the feedback circuit. Measurements of noise in both open- and closed-loop modes are shown and comparison is made with results from the model calculations

  18. Jet Engine Noise Generation, Prediction and Control. Chapter 86

    Huff, Dennis L.; Envia, Edmane


    Aircraft noise has been a problem near airports for many years. It is a quality of life issue that impacts millions of people around the world. Solving this problem has been the principal goal of noise reduction research that began when commercial jet travel became a reality. While progress has been made in reducing both airframe and engine noise, historically, most of the aircraft noise reduction efforts have concentrated on the engines. This was most evident during the 1950 s and 1960 s when turbojet engines were in wide use. This type of engine produces high velocity hot exhaust jets during takeoff generating a great deal of noise. While there are fewer commercial aircraft flying today with turbojet engines, supersonic aircraft including high performance military aircraft use engines with similar exhaust flow characteristics. The Pratt & Whitney F100-PW-229, pictured in Figure la, is an example of an engine that powers the F-15 and F-16 fighter jets. The turbofan engine was developed for subsonic transports, which in addition to better fuel efficiency also helped mitigate engine noise by reducing the jet exhaust velocity. These engines were introduced in the late 1960 s and power most of the commercial fleet today. Over the years, the bypass ratio (that is the ratio of the mass flow through the fan bypass duct to the mass flow through the engine core) has increased to values approaching 9 for modern turbofans such as the General Electric s GE-90 engine (Figure lb). The benefits to noise reduction for high bypass ratio (HPBR) engines are derived from lowering the core jet velocity and temperature, and lowering the tip speed and pressure ratio of the fan, both of which are the consequences of the increase in bypass ratio. The HBPR engines are typically very large in diameter and can produce over 100,000 pounds of thrust for the largest engines. A third type of engine flying today is the turbo-shaft which is mainly used to power turboprop aircraft and helicopters

  19. Distinct promoter activation mechanisms modulate noise-driven HIV gene expression

    Chavali, Arvind K.; Wong, Victor C.; Miller-Jensen, Kathryn


    Latent human immunodeficiency virus (HIV) infections occur when the virus occupies a transcriptionally silent but reversible state, presenting a major obstacle to cure. There is experimental evidence that random fluctuations in gene expression, when coupled to the strong positive feedback encoded by the HIV genetic circuit, act as a ‘molecular switch’ controlling cell fate, i.e., viral replication versus latency. Here, we implemented a stochastic computational modeling approach to explore how different promoter activation mechanisms in the presence of positive feedback would affect noise-driven activation from latency. We modeled the HIV promoter as existing in one, two, or three states that are representative of increasingly complex mechanisms of promoter repression underlying latency. We demonstrate that two-state and three-state models are associated with greater variability in noisy activation behaviors, and we find that Fano factor (defined as variance over mean) proves to be a useful noise metric to compare variability across model structures and parameter values. Finally, we show how three-state promoter models can be used to qualitatively describe complex reactivation phenotypes in response to therapeutic perturbations that we observe experimentally. Ultimately, our analysis suggests that multi-state models more accurately reflect observed heterogeneous reactivation and may be better suited to evaluate how noise affects viral clearance.

  20. Contemporary theories of 1/f noise in motor control.

    Diniz, Ana; Wijnants, Maarten L; Torre, Kjerstin; Barreiros, João; Crato, Nuno; Bosman, Anna M T; Hasselman, Fred; Cox, Ralf F A; Van Orden, Guy C; Delignières, Didier


    1/f noise has been discovered in a number of time series collected in psychological and behavioral experiments. This ubiquitous phenomenon has been ignored for a long time and classical models were not designed for accounting for these long-range correlations. The aim of this paper is to present and discuss contrasted theoretical perspectives on 1/f noise, in order to provide a comprehensive overview of current debates in this domain. In a first part, we propose a formal definition of the phenomenon of 1/f noise, and we present some commonly used methods for measuring long-range correlations in time series. In a second part, we develop a theoretical position that considers 1/f noise as the hallmark of system complexity. From this point of view, 1/f noise emerges from the coordination of the many elements that compose the system. In a third part, we present a theoretical counterpoint suggesting that 1/f noise could emerge from localized sources within the system. In conclusion, we try to draw some lines of reasoning for going beyond the opposition between these two approaches. PMID:21196059

  1. Quantum control with noisy fields: computational complexity versus sensitivity to noise

    A closed quantum system is defined as completely controllable if an arbitrary unitary transformation can be executed using the available controls. In practice, control fields are a source of unavoidable noise, which has to be suppressed to retain controllability. Can one design control fields such that the effect of noise is negligible on the time-scale of the transformation? This question is intimately related to the fundamental problem of a connection between the computational complexity of the control problem and the sensitivity of the controlled system to noise. The present study considers a paradigm of control, where the Lie-algebraic structure of the control Hamiltonian is fixed, while the size of the system increases with the dimension of the Hilbert space representation of the algebra. We find two types of control tasks, easy and hard. Easy tasks are characterized by a small variance of the evolving state with respect to the operators of the control operators. They are relatively immune to noise and the control field is easy to find. Hard tasks have a large variance, are sensitive to noise and the control field is hard to find. The influence of noise increases with the size of the system, which is measured by the scaling factor N of the largest weight of the representation. For fixed time and control field the ability to control degrades as O(N) for easy tasks and as O(N2) for hard tasks. As a consequence, even in the most favorable estimate, for large quantum systems, generic noise in the controls dominates for a typical class of target transformations, i.e. complete controllability is destroyed by noise. (paper)

  2. Active control of smart structures : an overall approach

    Nestorović Tamara; Trajkov Miroslav


    The paper presents active control of smart structures within a focused frame of piezoelectric applications in active vibration and noise attenuation with potentials for the use in mechanical and civil engineering. An overall approach to active control of piezoelectric structures involves subsequent steps of modeling, control, simulation, experimental verification and implementation. Each of these steps is regarded in details. Different application examples showing the feasibility of the activ...

  3. Delayed feedback as a means of control of noise-induced motion

    Janson, N. B.; A. G. Balanov; Schoell, E.


    Time--delayed feedback is exploited for controlling noise--induced motion in coherence resonance oscillators. Namely, under the proper choice of time delay, one can either increase or decrease the regularity of motion. It is shown that in an excitable system, delayed feedback can stabilize the frequency of oscillations against variation of noise strength. Also, for fixed noise intensity, the phenomenon of entrainment of the basic oscillation period by the delayed feedback occurs. This allows ...

  4. Noise control, sound, and the vehicle design process

    Donavan, Paul


    For many products, noise and sound are viewed as necessary evils that need to be dealt with in order to bring the product successfully to market. They are generally not product ``exciters'' although some vehicle manufacturers do tune and advertise specific sounds to enhance the perception of their products. In this paper, influencing the design process for the ``evils,'' such as wind noise and road noise, are considered in more detail. There are three ingredients to successfully dealing with the evils in the design process. The first of these is knowing how excesses in noise effects the end customer in a tangible manner and how that effects customer satisfaction and ultimately sells. The second is having and delivering the knowledge of what is required of the design to achieve a satisfactory or even better level of noise performance. The third ingredient is having the commitment of the designers to incorporate the knowledge into their part, subsystem or system. In this paper, the elements of each of these ingredients are discussed in some detail and the attributes of a successful design process are enumerated.

  5. Control of noise in magnetic multilayers by spin torque

    Rebei, Adnan


    In this work we show that the stability of magnetic nanostructures can be enhanced by time-dependent spin momentum transfer. Building reliable magnetic devices at smaller scales need to address the issue of thermal noise. Using two commonly studied magnetic systems with multiple stable states at zero temperature as examples, we show that periodic spin torques can enhance the stability of the system and hence suppress the noise due to interwell transitions. In the case of weak periodic spin torques, stochastic resonance which is usually associated with ac magnetic fields is also manifested for non-conservative torques. In more complex systems with a relatively low energy barrier, it is shown that high frequency spin torques can inhibit interwell transitions and in effect suppress the telegraph noise due to the switching between neigboring states.

  6. Noise shielding using active acoustic metamaterials with electronically tunable acoustic impedance

    Mokrý, P.; Steiger, Kateřina; Václavík, J.; Psota, Pavel; Doleček, Roman; Márton, P.; Kodejška, M.; Černík, M.

    Toowong DC QLD 4066: The Australian Acoustical Society, 2014 - (Davy, J.; Don, C.; McMinn, T.; Dowsett, L.; Broner, N.; Burgess, M.), s. 1-9 ISBN 978-0-909882-04-4. [Internoise 2014 Conference. Melbourne (AU), 16.11.2014-19.11.2014] R&D Projects: GA MŠk(CZ) LO1206; GA ČR GA13-10365S Institutional support: RVO:61389021 Keywords : Active Acoustic Metamaterial * Noise Shielding * Electronic Control of Acoustic Impedance Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  7. Effect of Unpleasant Loud Noise on Hippocampal Activities during Picture Encoding: An fMRI Study

    Hirano, Yoshiyuki; Fujita, Masafumi; Watanabe, Kazuko; Niwa, Masami; Takahashi, Toru; Kanematsu, Masayuki; Ido, Yasushi; Tomida, Mihoko; Onozuka, Minoru


    The functional link between the amygdala and hippocampus in humans has not been well documented. We examined the effect of unpleasant loud noise on hippocampal and amygdaloid activities during picture encoding by means of fMRI, and on the correct response in humans. The noise reduced activity in the hippocampus during picture encoding, decreased…

  8. Contemporary theories of 1/f noise in motor control

    Diniz, A.; Wijnants, M.L.; Torre, K.; Barreiros, J.; Crato, N.; Bosman, A.M.T.; Hasselman, F.; Cox, R.F.A.; Orden, G.C. van; Delignieres, D.


    1/f noise has been discovered in a number of time series collected in psychological and behavioral experiments. This ubiquitous phenomenon has been ignored for a long time and classical models were not designed for accounting for these long-range correlations. The aim of this paper is to present and

  9. Active Fluid Borne Noise Reduction for Aviation Hydraulic Pumps

    Waitschat, Arne; Thielecke, Frank; Behr, Robert M.; Heise, Ulrich


    The aviation environment holds challenging application constraints for efficient hydraulic system noise reduction devices. Besides strong limits on component weight and size, high safety and reliability standards demand simple solutions. Hence, basic silencers like inline expansion chambers and Helmholtz-Resonators are state-of-the-art aboard commercial aircrafts. Unfortunately, they do not meet today’s noise attenuation aims regarding passenger comfort and equipment durability. Significant a...

  10. Industrial Noise

    Mehran zolfaghari


    Various risk factors in industrial environments can affect hearing status and healthy in today’s modern society. Noise control and hearing conservation program is very crucial in preventing workers exposed to high levels of noise in the work places. In the current article we are going to discuss issues such as industrial noise control, noise characteristics and standards and techniques for noise control. Then the methods for individual hearing conservation and medical care will be described i...

  11. Noise-enhanced stability and double stochastic resonance of active Brownian motion

    Zeng, Chunhua; Zhang, Chun; Zeng, Jiakui; Liu, Ruifen; Wang, Hua


    In this paper, we study the transient and resonant properties of active Brownian particles (ABPs) in the Rayleigh-Helmholtz (RH) and Schweitzer-Ebeling-Tilch (SET) models, which is driven by the simultaneous action of multiplicative and additive noise and periodic forcing. It is shown that the cross-correlation between two noises (λ) can break the symmetry of the potential to generate motion of the ABPs. In case of no correlation between two noises, the mean first passage time (MFPT) is a monotonic decrease depending on the multiplicative noise, however in case of correlation between two noises, the MFPT exhibits a maximum, depending on the multiplicative noise for both models, this maximum for MFPT identifies the noise-enhanced stability (NES) effect of the ABPs. By comparing with case of no correlation (λ =0.0 ), we find two maxima in the signal-to-noise ratio (SNR) depending on the cross-correlation intensity, i.e. the double stochastic resonance is shown in both models. For the RH model, the SNR exhibits two maxima depending on the multiplicative noise for small cross-correlation intensity, while in the SET model, it exhibits only a maximum depending on the multiplicative noise. Whether λ =0.0 or not, the MFPT is a monotonic decrease, and the SNR exhibits a maximum, depending on the additive noise in both models.

  12. Inexact fuzzy integer chance constraint programming approach for noise control within an urban environment

    Huang, Kai; Huang, Gordon; Dai, Liming; Fan, Yurui


    This article introduces an inexact fuzzy integer chance constraint programming (IFICCP) approach for identifying noise reduction strategy under uncertainty. The IFICCP method integrates the interval programming and fuzzy chance constraint programming approaches into a framework, which is able to deal with uncertainties expressed as intervals and fuzziness. The proposed IFICCP model can be converted into two deterministic submodels corresponding to the optimistic and pessimistic conditions. The modelling approach is applied to a hypothetical control measure selection problem for noise reduction. Results of the case study indicate that useful solutions for noise control practices can be acquired. Three acceptable noise levels for two communities are considered. For each acceptable noise level, several decision alternatives have been obtained and analysed under different fuzzy confidence levels, which reflect the trade-offs between environmental and economic considerations.

  13. Visual signal detection in structured backgrounds. II. Effects of contrast gain control, background variations, and white noise

    Eckstein, M. P.; Ahumada, A. J. Jr; Watson, A. B.


    Studies of visual detection of a signal superimposed on one of two identical backgrounds show performance degradation when the background has high contrast and is similar in spatial frequency and/or orientation to the signal. To account for this finding, models include a contrast gain control mechanism that pools activity across spatial frequency, orientation and space to inhibit (divisively) the response of the receptor sensitive to the signal. In tasks in which the observer has to detect a known signal added to one of M different backgrounds grounds due to added visual noise, the main sources of degradation are the stochastic noise in the image and the suboptimal visual processing. We investigate how these two sources of degradation (contrast gain control and variations in the background) interact in a task in which the signal is embedded in one of M locations in a complex spatially varying background (structured background). We use backgrounds extracted from patient digital medical images. To isolate effects of the fixed deterministic background (the contrast gain control) from the effects of the background variations, we conduct detection experiments with three different background conditions: (1) uniform background, (2) a repeated sample of structured background, and (3) different samples of structured background. Results show that human visual detection degrades from the uniform background condition to the repeated background condition and degrades even further in the different backgrounds condition. These results suggest that both the contrast gain control mechanism and the background random variations degrade human performance in detection of a signal in a complex, spatially varying background. A filter model and added white noise are used to generate estimates of sampling efficiencies, an equivalent internal noise, an equivalent contrast-gain-control-induced noise, and an equivalent noise due to the variations in the structured background.

  14. Multichannel control systems for the attenuation of interior road noise in vehicles

    Cheer, Jordan; Elliott, Stephen J.


    This paper considers the active control of road noise in vehicles, using either multichannel feedback control, with both headrest and floor positioned microphones providing feedback error signals, or multichannel feedforward control, in which reference signals are provided by the microphones on the vehicle floor and error signals are provided by the microphones mounted on the headrests. The formulation of these control problems is shown to be similar if the constraints of robust stability, limited disturbance enhancement and open-loop stability are imposed. A novel formulation is presented for disturbance enhancement in multichannel systems, which limits the maximum enhancement of each individual error signal. The performance of these two systems is predicted using plant responses and disturbance signals measured in a small city car. The reduction in the sum of the squared pressure signals at the four error microphones for both systems is found to be up to 8 dB at low frequencies and 3 dB on average, where the sound level is particularly high from 80 to 180 Hz. The performance of both systems is found to be robust to measured variations in the plant responses. The enhancements in the disturbance at higher frequencies are smaller for the feedback controller than for the feedforward controller, although the performance of the feedback controller is more significantly reduced by the introduction of additional delay in the plant response.

  15. A Kalman filter for feedback control of rotating external kink instabilities in the presence of noise

    The simulation and experimental optimization of a Kalman filter feedback control algorithm for n=1 tokamak external kink modes are reported. In order to achieve the highest plasma pressure limits in ITER, resistive wall mode stabilization is required [T. C. Hender et al., Nucl. Fusion 47, S128 (2007)] and feedback algorithms will need to distinguish the mode from noise due to other magnetohydrodynamic activity. The Kalman filter contains an internal model that captures the dynamics of a rotating, growing n=1 mode. This model is actively compared with real-time measurements to produce an optimal estimate for the mode's amplitude and phase. On the High Beta Tokamak-Extended Pulse experiment [T. H. Ivers et al., Phys. Plasmas 3, 1926 (1996)], the Kalman filter algorithm is implemented using a set of digital, field-programmable gate array controllers with 10 μs latencies. Signals from an array of 20 poloidal sensor coils are used to measure the n=1 mode, and the feedback control is applied using 40 poloidally and toroidally localized control coils. The feedback system with the Kalman filter is able to suppress the external kink mode over a broad range of phase angles between the sensed mode and applied control field. Scans of filter parameters show good agreement between simulation and experiment, and feedback suppression and excitation of the kink mode are enhanced in experiments when a filter made using optimal parameters from the scans is used.

  16. Electrical Maxwell Demon and Szilard Engine Utilizing Johnson Noise, Measurement, Logic and Control

    Kish, Laszlo Bela; Granqvist, Claes-Göran


    We introduce a purely electrical version of Maxwell's demon which does not involve mechanically moving parts such as trapdoors, etc. It consists of a capacitor, resistors, amplifiers, logic circuitry and electronically controlled switches and uses thermal noise in resistors (Johnson noise) to pump heat. The only types of energy of importance in this demon are electrical energy and heat. We also demonstrate an entirely electrical version of Szilard's engine, i.e., an information-controlled dev...

  17. Active absorber for damping audio-frequency noise emissions at wind power plants. Active vibration damping; Aktiver Tilger zur Unterdrueckung tonaler Schallemissionen an Windenergieanlagen. Aktive Schwingungstilgung

    Neugebauer, R.; Linke, M.; Kunze, H.; Ullrich, M. [Fraunhofer Institut fuer Werkzeugmaschinen und Umformtechnik (IWU), Chemnitz / Dresden (Germany)


    Structural vibrations of a wind turbine's drive train are one of the main reasons for noise emissions. Mechanical vibrations are transferred through the structure and emitted as noise by large surfaces, e.g. tower and nacelle. Dominant vibration excitation is caused for example by the gear mesh. If the gear mesh frequency is coinciding with the frequency of a structural resonance, the emitted noise contains noticeable single tones. German immission control law requires a ''tonal penalty'' up to 6 dB, if the emitted noise contains annoying tones. To ensure compliance with immission limits those tones must be reduced or eliminated. For wind turbines running with variable speed an active vibration absorber has been developed, whose absorber frequency and damping is adapted corresponding to the alternating vibration excitation. (orig.)

  18. THACO, a Test Facility for Characterizing the Noise Performance of Active Antenna Arrays

    Woestenburg, E E M; Ruiter, M; Ivashina, M V; Witvers, R H


    This paper discusses an outdoor test facility for the noise characterization of active antenna arrays, using measurement results of array noise temperatures in the order of 50 K for a number of small aperture arrays. The measurement results are obtained by a Y-factor method with hot and a cold noise sources, with an absorber at room temperature as the hot load and the cold sky as the cold load. The effect of shielding the arrays by the test facility, with respect to noise and RFI from the environment, will also be discussed.

  19. Electromyographic Activity in the EEG in Alzheimer's Disease: Noise or Signal?

    Karin van der Hiele


    Full Text Available Many efforts have been directed at negating the influence of electromyographic (EMG activity on the EEG, especially in elderly demented patients. We wondered whether these “artifacts” might reflect cognitive and behavioural aspects of dementia. In this pilot study, 11 patients with probable Alzheimer's disease (AD, 13 with amnestic mild cognitive impairment (MCI and 13 controls underwent EEG registration. As EMG measures, we used frontal and temporal 50–70 Hz activity. We found that the EEGs of AD patients displayed more theta activity, less alpha reactivity, and more frontal EMG than controls. Interestingly, increased EMG activity indicated more cognitive impairment and more depressive complaints. EEG variables on the whole distinguished better between groups than EMG variables, but an EMG variable was best for the distinction between MCI and controls. Our results suggest that EMG activity in the EEG could be more than noise; it differs systematically between groups and may reflect different cerebral functions than the EEG.

  20. Resonant-Like Activation in a Bistable System with Noise and Time Delay

    NIE Lin-Ru; GONG Ai-Ling; MEI Dong-Cheng


    A bistable system with noise and time delay is investigated.Theoretical analysis and stochastic simulation show that:(i) In the case of a system driven only by multiplicative Gaussian white noise,the mean first-passage time for a particle to reach the other stable state from one stable state exhibits a minimum with respect to delay time,i.e.,a resonant-like activation (RA) phenomenon.(ii) In the action of additive and multiplicative noise,as the additive noise intensity increases,no matter whether a correlation between the two types of noise exists or not,the RA gradually disappears.(iii) The correlation strength between the two types of noise does not influence the existence of the RA.

  1. Noise filtering algorithm for the MFTF-B computer based control system

    An algorithm to reduce the message traffic in the MFTF-B computer based control system is described. The algorithm filters analog inputs to the control system. Its purpose is to distinguish between changes in the inputs due to noise and changes due to significant variations in the quantity being monitored. Noise is rejected while significant changes are reported to the control system data base, thus keeping the data base updated with a minimum number of messages. The algorithm is memory efficient, requiring only four bytes of storage per analog channel, and computationally simple, requiring only subtraction and comparison. Quantitative analysis of the algorithm is presented for the case of additive Gaussian noise. It is shown that the algorithm is stable and tends toward the mean value of the monitored variable over a wide variety of additive noise distributions

  2. A noise filtering algorithm for the MFTF-B computer based control system

    An algorithm to reduce the message traffic in the MFTF-B computer based control system is described. The algorithm filters analog inputs to the control system. Its purpose is to distinguish between changes in the inputs due to noise and changes due to significant variations in the quantity being monitored. Noise is rejected while significant changes are reported to the control system data base, thus keeping the data base updated with a minimum number of messages. The algorithm is memory efficient, requiring only four bytes of storage per analog channel, and computationally simple, requiring only subtraction and comparison. Quantitative analysis of the algorithm is presented for the case of additive Gaussian noise. It is shown that the algorithm is stable and tends toward the mean value of the monitored variable over a wide variety of additive noise distributions

  3. Transient finite element simulations and experiments on active control of sound transmission loss through plates

    Brink, Maarten Cornelis


    In this thesis the sound transmission loss of a plate has been investigated. It serves as an abstract model for the noise barrier between engine and passengers in a bus. A finite element simulation model has been developed to be able to predict the plate's noise reduction effect. To increase this reduction without adding too much mass, the integration of active noise control (ANC) has been investigated. The active system contained a controller, microphones and piezoelectric actuators. The inf...

  4. Introducing the Standard and Chart to Measure and Control the Motorcycle Noise Level

    S Farhang Dehghan


    Full Text Available Background and Objectives: Sound of motorcycles plays an important role in noise pollution in big cities. This is due to the lack of national law or standards to control the noise of domestic and also imported motorcycles. This study tries to introduce a practical limit value in different stage of motorcycle life cycle by assessing their noise pollution. Materials and Methods: First the motorcycles noise standards at different countries were studied and they were compared with the results from noise level of 622 motorcycles in 3 different groups. The sample volume in each group corresponds to the amount of their annual production rate. Then using statistical tests, a limit was determined in which 90% of the domestic motorcycles can be covered. The limit is proposed as the standard for domestic motorcycle noise.Results: The limit for motorcycles of groups 1, 2 and 3were 84, 86 and 87 dB (A ,respectively in the TA stage. For the COP stage (Conformity of Production, the limit increases according to certain formula. In the end, a flowchart was proposed as a standard method for measuring the sound of motorcycles in the TA and COP stages was proposed.Conclusion: Noise level of the domestic motorcycles is at least 9 dB (A higher than the noise limit value of European motorcycle. If European limit value is considered for producing the national motorcycle, 90% of them will get out of production cycle and this would not be practical.

  5. Low noise frequency synthesizer with self-calibrated voltage controlled oscillator and accurate AFC algorithm

    A low noise phase locked loop (PLL) frequency synthesizer implemented in 65 nm CMOS technology is introduced. A VCO noise reduction method suited for short channel design is proposed to minimize PLL output phase noise. A self-calibrated voltage controlled oscillator is proposed in cooperation with the automatic frequency calibration circuit, whose accurate binary search algorithm helps reduce the VCO tuning curve coverage, which reduces the VCO noise contribution at PLL output phase noise. A low noise, charge pump is also introduced to extend the tuning voltage range of the proposed VCO, which further reduces its phase noise contribution. The frequency synthesizer generates 9.75–11.5 GHz high frequency wide band local oscillator (LO) carriers. Tested 11.5 GHz LO bears a phase noise of−104 dBc/Hz at 1 MHz frequency offset. The total power dissipation of the proposed frequency synthesizer is 48 mW. The area of the proposed frequency synthesizer is 0.3 mm2, including bias circuits and buffers. (semiconductor integrated circuits)

  6. Environmental noise levels affect the activity budget of the Florida manatee

    Miksis-Olds, Jennifer L.; Donaghay, Percy L.; Miller, James H.; Tyack, Peter L.


    Manatees inhabit coastal bays, lagoons, and estuaries because they are dependent on the aquatic vegetation that grows in shallow waters. Food requirements force manatees to occupy the same areas in which human activities are the greatest. Noise produced from human activities has the potential to affect these animals by eliciting responses ranging from mild behavioral changes to extreme aversion. This study quantifies the behavioral responses of manatees to both changing levels of ambient noise and transient noise sources. Results indicate that elevated environmental noise levels do affect the overall activity budget of this species. The proportion of time manatees spend feeding, milling, and traveling in critical habitats changed as a function of noise level. More time was spent in the directed, goal-oriented behaviors of feeding and traveling, while less time was spent milling when noise levels were highest. The animals also responded to the transient noise of approaching vessels with changes in behavioral state and movements out of the geographical area. This suggests that manatees detect and respond to changes in environmental noise levels. Whether these changes legally constitute harassment and produce biologically significant effects need to be addressed with hypothesis-driven experiments and long-term monitoring. [For Animal Bioacoustics Best Student Paper Award.

  7. Optimal Flight for Ground Noise Reduction in Helicopter Landing Approach: Optimal Altitude and Velocity Control

    Tsuchiya, Takeshi; Ishii, Hirokazu; Uchida, Junichi; Gomi, Hiromi; Matayoshi, Naoki; Okuno, Yoshinori

    This study aims to obtain the optimal flights of a helicopter that reduce ground noise during landing approach with an optimization technique, and to conduct flight tests for confirming the effectiveness of the optimal solutions. Past experiments of Japan Aerospace Exploration Agency (JAXA) show that the noise of a helicopter varies significantly according to its flight conditions, especially depending on the flight path angle. We therefore build a simple noise model for a helicopter, in which the level of the noise generated from a point sound source is a function only of the flight path angle. Using equations of motion for flight in a vertical plane, we define optimal control problems for minimizing noise levels measured at points on the ground surface, and obtain optimal controls for specified initial altitudes, flight constraints, and wind conditions. The obtained optimal flights avoid the flight path angle which generates large noise and decrease the flight time, which are different from conventional flight. Finally, we verify the validity of the optimal flight patterns through flight experiments. The actual flights following the optimal paths resulted in noise reduction, which shows the effectiveness of the optimization.

  8. Fault-tolerant controlled quantum secure direct communication over a collective quantum noise channel

    This work proposes controlled quantum secure direct communication (CQSDC) over an ideal channel. Based on the proposed CQSDC, two fault-tolerant CQSDC protocols that are robust under two kinds of collective noises, collective-dephasing noise and collective-rotation noise, respectively, are constructed. Due to the use of quantum entanglement of the Bell state (or logical Bell state) as well as dense coding, the proposed protocols provide easier implementation as well as better qubit efficiency than other CQSDC protocols. Furthermore, the proposed protocols are also free from correlation-elicitation attack and other well-known attacks. (paper)

  9. High precision measurement of transistor noise with automatic calibration under computer control

    The preliminary selection of transistors for use in low noise pre-amplifiers requires the measurement of the equivalent noise voltage under various operating conditions including the temperature. Available equipment often lacks the necessary precision and is difficult to calibrate, especially when the device temperature is varied. Such equipment requires skill and patience from the operator. The authors describe a micro-computer controlled equipment which can measure transistor noise in the frequency range 10Hz to 100kHz to a greater accuracy than that previously obtainable. The transistor temperature and operating conditions may be scanned automatically over a wide range. Each measurement is internally calibrated

  10. The effect of human activities and their associated noise on ungulate behavior.

    Casey L Brown

    Full Text Available BACKGROUND: The effect of anthropogenic noise on terrestrial wildlife is a relatively new area of study with broad ranging management implications. Noise has been identified as a disturbance that has the potential to induce behavioral responses in animals similar to those associated with predation risk. This study investigated potential impacts of a variety of human activities and their associated noise on the behavior of elk (Cervus elaphus and pronghorn (Antilocapra americana along a transportation corridor in Grand Teton National Park. METHODOLOGY/PRINCIPAL FINDINGS: We conducted roadside scan surveys and focal observations of ungulate behavior while concurrently recording human activity and anthropogenic noise. Although we expected ungulates to be more responsive with greater human activity and noise, as predicted by the risk disturbance hypothesis, they were actually less responsive (less likely to perform vigilant, flight, traveling and defensive behaviors with increasing levels of vehicle traffic, the human activity most closely associated with noise. Noise levels themselves had relatively little effect on ungulate behavior, although there was a weak negative relationship between noise and responsiveness in our scan samples. In contrast, ungulates did increase their responsiveness with other forms of anthropogenic disturbance; they reacted to the presence of pedestrians (in our scan samples and to passing motorcycles (in our focal observations. CONCLUSIONS: These findings suggest that ungulates did not consistently associate noise and human activity with an increase in predation risk or that they could not afford to maintain responsiveness to the most frequent human stimuli. Although reduced responsiveness to certain disturbances may allow for greater investment in fitness-enhancing activities, it may also decrease detections of predators and other environmental cues and increase conflict with humans.