Abstract: A control system for reducing noise or vibration in a target zone. The noise or vibration is produced by a source and transferred to the target zone by a main path. The control system is provided with an actuator, at least one error sensor and a controller. The actuator is positioned to deliver actuated signals into at least a portion of the target zone. The at least one error sensor monitors the residual noise or vibration power in the target zone and produces an error signal representative thereof. The controller receives a reference signal representative of noise or vibration produced by the source, and the error signal representative of the residual noise power in the target zone. The controller analyzes sub-bands of the reference signal and the error signal without identification of a secondary path, and provides drive signals to the actuator to cause the actuator to deliver the actuated signals into the target zone so as to reduce the residual noise power in the target zone.

Abstract: Reflection cancelling boundary microphones are described in which a microphone capsule is mounted within the pressure zone of a vibrating surface and the microphone is tuned in such a way as to cancel pressure waves reflected by the surface while admitting pressure waves generated by the vibration of the surface. One embodiment of the invention includes a microphone capsule configured to be mounted within the pressure zone of a vibrating surface. In addition, the microphone is tuned to cancel pressure waves reflected by the surface while admitting pressure waves generated by the vibration of the surface.

Abstract: A noise control device includes the following structural elements. A signal memory records both of a noise signal supplied from a noise microphone and an error signal supplied from an error microphone. A filter coefficient calculator calculates a fixed filter coefficient of a control filter by using data recorded in the signal memory. A filter coefficient renewing section renews, at a given timing, a filter coefficient set at a fixed filter in a control filter to a filter coefficient read out from the filter coefficient calculator.

Abstract: The present invention relates to an active muffler for an exhaust gas system of an internal combustion engine, in particular in a motor vehicle, having at least one antinoise generator for applying antinoise to the exhaust gas, whereby the antinoise generator has a diaphragm drive with which it is coupled via at least one coupling element in a thermally conducting and noise-reducing manner to an outside wall of the muffler, which is in contact with the environment.

Abstract: A device for actively reducing sound transmission, provided with a first and second wall (3, 5) enclosing an inner space (1, 2), wherein at least the second wall (5) is provided with actuators (6), for instance eletromagnetic actuators and/or piezoeleteric elements, wherein the said inner space is provided with at least one inner wall (4) to divide this space into at least two layers of air (1, 2), which inner wall (4) is arranged such that the layers of air (1, 2) are in fluid connection with each other.

Abstract: A system and method for localized noise cancellation. An audio signal is received from an environment in close proximity to a primary area. The audio signal is processed to generate an inverse signal of the audio signal. The inverse signal is broadcast within the primary area to destructively interfere with the audio signal. The inverse signal is configured to prevent the audio signal from being broadcast through a telephone conversation ongoing in the primary area.

Abstract: The present invention provides an active control type noise reducing device that is disposed at a sound barrier and with which can be obtained an excellent noise reduction effect with respect to moving sound sources. Linear array of flat loudspeakers are arranged in ascending order from an incoming side of automobiles towards an outgoing side. Delay times of 0, ?, 2?, . . . , 8? are respectively given in the arrangement order to the linear array of flat loudspeakers. By delaying signals in correspondence to the arrangement order, the wavefront of a control sound can be slanted in a diagonal direction. Namely, “line sound sources”, where sound sources are linearly arranged, arc pseudo-realized.

Abstract: Effective reduction is made of direct sound or diffracted sound of a noise propagating from plural directions. Three microphones (18k?1, 18k, 18k+1) are disposed and: noise is detected by each of the microphones; delay signals are generated by delaying plural times a signal that has been output from 2 of the microphones (18k?1, 18k+1); the output signal from the remaining microphone (18k) is added to 2 of the delayed signals and input to respective speakers of a speaker unit; a control sound is output from the speaker unit in 3 directions (L, C, R); and reduction is made of direct sound or diffracted sound of a noise propagating from each of the directions.

Abstract: A method for counteracting the occlusion effect of an electronic device delivering an audio signal to the ear, like a hearing aid or an active ear protector, where the electronic device includes a transmission path with an external microphone or input line which receives a signal from the environment and an signal processor and a receiver which receives processes signal from the signal from the signal processor and delivers sound signals to the ear, whereby an ear piece is inserted into the ear canal and totally or partially blocks the canal. The sound conditions in the cavity between the ear piece and the tympanic membrane are directly or indirectly determined, and whenever condition leading to occlusion problems are determined, the transmission characteristics of the transmission path or the receiver changes in order to counteract the occlusion effect.

Abstract: A system for reducing noise induced from a chassis is described. The system comprises a signal processing engine, a first microphone connected to a chassis and communicatively coupled to the signal processing engine, a dampener connected to the chassis, and a second microphone connected to the dampener and communicatively coupled to the signal processing engine.

Abstract: Communication systems and apparatus to allow a user to perceive the relative spatial location or present position of other elements of interest in a control space, such as the location of a speaker participating in a telephone conference or that of an aircraft carrier to a remotely piloted vehicle on final approach. The system inserts synthetic sound cues into the communication to the user that represent the relative position(s). In one embodiment, the user will perceive the communication as though it were communicated through free space to the user from the relative position of the represented source, so that, for example, the squad leader will perceive his wingman to be at his immediate left. Methods of conveying relative position sound cues are also provided.

Abstract: An acoustic vibration sensor, also referred to as a speech sensing device, is provided. The acoustic vibration sensor receives speech signals of a human talker and, in response, generates electrical signals representative of human speech. The acoustic vibration sensor includes at least one diaphragm positioned adjacent to a front port and at least one coupler. The coupler couples a first set of signals to the diaphragm while isolating the diaphragm from the second set of signals. The coupler includes at least one material with acoustic impedance matched to the acoustic impedance of human skin.

Abstract: An ambient noise removing apparatus and method and a mobile communication terminal having the same are provided for removing a noise from a valid tone source with the noise inputted via a microphone or sensor The invention comprises reference current setting unit tor setting a reference current from a tone source inputted via a microphone or sensor, a variable amplifier having a gain controlled by the set reference current and for amplifying an input current of the tone source depending on the gain, and a level adjuster for adjusting a level of the tone source amplified through the variable amplifier

Abstract: An apparatus for attenuating noise emanating from a cabinet housing noise-generating equipment includes a frame including at least one support member configured to be mountable on the cabinet, proximate the noise-generating equipment, at least one noise attenuation device mounted to each support member proximate the noise-generating equipment, the at least one noise attenuation device comprising a sound input device for receiving a noise signal output from the noise-generating equipment, a processing device for determining characteristics of the noise signal and generating a cancellation signal which is identical to the noise signal but approximately 180 degrees out-of-phase with the noise signal, and a sound output device for outputting the cancellation signal proximate the noise-generating equipment, to attenuate the noise emanating from the cabinet; and a noise absorption member mounted on each support member, the noise absorption members define surfaces that form sides of airflow channels through the appa

Abstract: An active sound muffler for reducing a sound to be reduced as emitted from a sound source located at one of the opposite sides of a sound insulating wall and diffracted and transmitted to the other side, the muffler comprises a control loudspeaker arranged at the front end or the other side of the sound insulating wall and adapted to output a control sound with a predetermined amplitude and a predetermined phase, a control microphone arranged above the sound insulating wall and adapted to gauge the sound pressure or the acoustic intensity of the sound to be reduced and that of the control sound and a control circuit for controlling the output of the control loudspeaker so as to minimize the sound pressure or the acoustic intensity, whichever appropriate, based on the outcome of gauging of the control microphone, and the control loudspeaker showing a line sound source characteristic.

Abstract: In a mail handling machine comprising a succession of modules disposed along a conveyor path for conveying mail items from a feed module for feeding in mail items to a collection module for collecting mail items that have been franked by passing through a franking module for printing postage imprints on said mail items, there is provided at least one sound acquisition means for picking up noise emitted inside one of said modules, and sound generation means for generating counter-noise in said module so as to proceed with canceling said emitted noise and thus reducing the overall noise level of the mail handling machine.

Abstract: An active noise control system is provided which cancels a noise using a secondary noise from a speaker that is operated in accordance with an output from an adaptive controller. The system is configured such that microphone monitor interrupts a switch to thereby stop the secondary noise from being produced, when an error signal delivered by a microphone used for an adaptive computation in an LMS processing portion has the same sign for a predetermined duration. This allows the system to prevent the user from hearing an abnormal acoustic noise resulting from an abnormal operation or divergence of an adaptive filter even when the output signal from the microphone used for the adaptive computation is indicative of an abnormal level.

Abstract: A sound system obtains a desired sound field from an array of sound sources arranged on a panel. The desired sound field allows a listener to perceive the sound as if the sound were coming from a live source and from a specified location. Setup of the sound system includes arranging a microphone array adjacent the array of sound sources to obtain a generated sound field. Arbitrary finite impulse response filters are then composed for each sound source within the array of sound sources. Iteration is applied to optimize filter coefficients such that the generated sound field resembles the desired sound field so that multi-channel equalization and wave field synthesis occur. After the filters are setup, the microphones may be removed.

Abstract: A system and method of reducing noise in an enclosure is disclosed. The method includes receiving at least one reference signal; receiving pressure signals from no more than two substantially orthogonally placed pairs of acoustic sensors, where one pair of acoustic sensors is in the x-direction and one pair of acoustic sensors is in the y-direction, and where the acoustic sensors are placed in a plane which is substantially parallel and in proximity to an inner surface of the enclosure; using the pressure signals and the reference signal to generate an output signal to minimize energy density at a location of the acoustic sensors; and sending the output signal to an acoustic actuator.

Abstract: A refrigerated appliance that dispenses items for use with a power source and includes a cooling system. Power control circuitry is electrically coupled between the power source and components (for example, a compressor and one or more circulating fans of the cooling system) of the appliance. A controller, which is operably coupled to the power control circuitry, is adapted to manage the supply of electrical power to such components by intelligently transitioning between a normal-operation mode and at least one power-conserving mode. To achieve efficient power conservation, an audio signal detector is provided that generates at least one dispensing event signal that represents the occurrence of one or more sound-based dispensing events. The controller automatically transitions between the power-conserving mode(s) and the normal-operation mode based upon at least one dispensing event data signal supplied to the controller by the audio signal detector, and possibly other data signals supplied to the controller.

Abstract: A system for reducing the vibration sensitivity of an implantable microphone without an equal or greater reduction in sound sensitivity. The system reduces non-ambient vibrations by placing at least one compliant member into the path of transmission for tissue-borne vibration, but not into the path for ambient sound-induced vibration. More particularly, a compliant member is interposed along the path between a source of non-ambient vibration and an implanted microphone. In one aspect, a compliant base member is disposed between an implanted microphone and an implant wearer's skull. In another aspect, a microphone is compliantly suspended relative to an implant housing using a support membrane. In either aspect, the compliant member (i.e., base member and/or membrane) and the supported member (i.e., housing and/or microphone) define a supported system having a natural or resonant frequency. This natural frequency may be set to a value to advantageously isolate the microphone against transmitted vibration.

Abstract: Communication systems and apparatus to allow a user to perceive the relative spatial location or present position of other elements of interest in a control space, such as the location of a speaker participating in a telephone conference or that of an aircraft carrier to a remotely piloted vehicle on final approach. The system inserts synthetic sound cues into the communication to the user that represent the relative postion(s). In one embodiment, the user will perceive the communication as though it were communicated through free space to the user from the relative position of the represented source, so that, for example, the squad leader will perceive his wingman to be at his immediate left. Methods of conveying relative position sound cues are also provided.

Abstract: An implanted microphone is provided that has reduced sensitivity to vibration and attendant acceleration forces. In this regard, the microphone differentiates between the desirable and undesirable components of a transcutaneously received signal. More specifically, the present invention utilizes an output that is indicative of acceleration forces acting on the implanted microphone (e.g., an acceleration signal) to counteract and/or cancel the effects of acceleration induced pressures in an output signal of a microphone diaphragm. This may be done in a variety of ways, including but not limited to, pneumatically, mechanically, electrical analog, or digitally, or combinations thereof. In one arrangement, the generated output may be filtered to match the an acceleration response of the output signal of the microphone diaphragm such that upon removal of the motion signal from the microphone output, the remaining signal is an acoustic signal.

Abstract: A system and process for estimating the time delay of arrival (TDOA) between a pair of audio sensors of a microphone array is presented. Generally, a generalized cross-correlation (GCC) technique is employed. However, this technique is improved to include provisions for both reducing the influence (including interference) from correlated ambient noise and reverberation noise in the sensor signals prior to computing the TDOA estimate. Two unique correlated ambient noise reduction procedures are also proposed. One involves the application of Wiener filtering, and the other a combination of Wiener filtering with a Gnn subtraction technique. In addition, two unique reverberation noise reduction procedures are proposed. Both involve applying a weighting factor to the signals prior to computing the TDOA which combines the effects of a traditional maximum likelihood (TML) weighting function and a phase transformation (PHAT) weighting function.

Abstract: A method and system that reduces undesired vibration in a vehicle measures ambient vibration and generates a first command signal based upon the measured vibration. If a first component of the first command signal exceeds a maximum allowable, the first component of the first command signal must be constrained. A residual vibration resulting from the constraint of the first component is then calculated. A second command signal to compensate for the residual vibration is then calculated. Force generators are then activated based upon the constrained first component and the second command signal in order to reduce the vibration.

Abstract: An active noise cancellation system includes a series of features for more effective cancellation, greater reliability, and improved stability. A particular feature adapted for headset systems includes locating a residual microphone radially offset from the center of a sound generator to detect a signal more similar to that incident upon the eardrum of the user. In addition, an open back headset design includes perforations on the side of the headset instead of the back, so that the perforations are less susceptible to inadvertent blockage. The system also includes a mechanism for detecting changes in the acoustic characteristics of the environment that may be caused, for example, by pressure exerted upon the earpieces, and that may destabilize the cancellation system. The system automatically responds to such changes, for example, by reducing the gain or the frequency response of the system to preserve stability.

Abstract: A method of detecting and locating noise sources each emitting respective signals Sj with j=1 to M, detection being provided by a sound wave or vibration sensors each delivering a respective time-varying electrical signal si with i in the range 1 to N, wherein the method steps include: (a) taking the time-varying electrical signals delivered by the sensors, each signal si(t) delivered by a sensor being the sum of the signals Sj emitted by the noise sources; (b) amplifying and filtering the time-varying electrical signals as taken; (c) digitizing the electrical signals; (d) calculating a functional; and (e) minimizing the functional relative to the vectors nj for j=1 to M so as to determine the directions of vector nj of the noise sources.

Abstract: The active/passive absorber for extended vibration and sound radiation control includes principally two layers. The first layer has a low stiffness per unit area which allows motion in the direction perpendicular to its main plane. The second layer is principally a mass layer. These two combined layers have a frequency of resonance close to one of the main structure. The dynamic behavior of the coupled system makes the active/passive absorber a passive absorber; however, the first layer can be electrically actuated to induce motion in the direction perpendicular to its main plane. This addition property induces and/or changes the motion of the mass layer and therefore improves the dynamic properties of the active/passive absorber system. The acive/passive absorber can have multiple mass layers and multiple elastic layers stacked one on top of the other. In addition, the mass layers can be continuous or discretized, and have varying thicknesses and shapes for sections and/or segments in the mass layer.

Abstract: A vibration control system for an engine or transmission cover on a motor vehicle to absorb and dissipate gear or chain-induced vibration uses a piezoelectric strain actuator with a passive resonant control system to absorb and dissipate vibration at a fixed resonance frequency of transmission and engine timing covers. Another embodiment uses an open-loop active control system, based on signals already existing on-board in the engine controller and a control map of phase, amplitude and frequency. Still another embodiment employs a hybrid system, combining open- and closed-loop control.

Abstract: An active diffracted sound control apparatus comprises a reference microphone for measuring the noise information on a noise source side of a sound insulating wall, a first error microphone for measuring the noise information on a noise receiving side of the sound insulating wall, a speaker arranged in the neighborhood of the sound insulating wall K for generating a control sound to reduce the object sound at a sound receiving point, and a control unit for controlling the output of the speaker based on the outputs of the reference microphone and the first error microphone. The control unit is operated based on a first sound transmission characteristic between the first error microphone and the second error microphone for the noise source and a second sound transmission characteristic between the first error microphone and the second error microphone for the speaker.

Abstract: An adaptive noise canceling system for extracting a desired signal, comprising an adaptive noise cancellation filtering circuit for suppressing noise from a first input signal using a second input signal as a reference signal, and generating an output filtered signal representing the desired signal; and an adaptive noise cancellation controller for receiving the first and second input signals and the output filtered signal, and generating an output control signal for controlling coefficients of at least one adaptive filter of the adaptive noise cancellation filtering circuit, comprising a silence detector unit for detecting whether an acoustical signal is present in the input signals and the output filtered signal, and generating a first output signal which indicates whether the acoustical signal is present; a signal detector unit for detecting whether the desired signal is present in the input signals and the output filtered signal, and generating a second output signal which indicates whether the desired si

Abstract: For locating, identifying and classifying noise sources inside and outside spaces, the invention provides a method for processing noise signals of a noise source, in which a plurality of noise signals (SQ1 to SQ4) are detected in a location-related manner and examined by means of a sound analysis on the basis of signal features in such a way that parameters underlying the noise source (G1 to G4) are determined.

Abstract: A noise reduction apparatus for reducing noise propagated toward a space 5 on one side of a wall 4 from an external noise source on the other side of the wall 4. The noise reduction apparatus includes a control sound source 1, an error detector 2, and a control section 3. The control sound source 1 is placed on the wall 4 so as to block a noise propagation path. Also, the control sound source radiates a sound into the space 5. The error detector 2 detects the sound propagated from the noise source through the control sound source 1. The control section 3 causes the control sound source 1 to radiate a sound so as to minimize the sound to be detected by the error detector 2 based on the detection results of the error detector 2.

Abstract: The active/passive absorber for extended vibration and sound radiation control includes principally two layers. The first layer has a low stiffness per unit area which allows motion in the direction perpendicular to its main plane. The second layer is principally a mass layer. These two combined layers have a frequency of resonance close to one of the main structure. The dynamic behavior of the coupled system makes the active/passive absorber a passive absorbe; however, the first layer can be electrically actuated to induce motion in the direction perpendicular to its main plane. This addition property induces and/or changes the motion of the mass layer and therefore improves the dynamic properties of the active/passive absorber system.

Abstract: An active noise control system (20) includes a controller (26) that drives a speaker (28) to cancel out or reduce noise. A microphone (30) provides information to the controller (26) regarding the system response to the noise source sound and the cancellation signal. The controller (26) uses a selected noise source sound as a calibration reference. By subsequently comparing the system response to the same sound, the controller (26) is able to calibrate the system and make any adjustments necessary to account for microphone drift, for example.

Abstract: A system for identifying a model of an acoustic system in the presence of an external noise signal is disclosed. The system includes an acoustic actuator for generating controlled sound within the acoustic system. A sensor receives the controlled sound and the external noise signal and produces a sensed signal. A control system generates a control signal in response to an error signal. The control system includes a system model for generating an estimated response signal. The control system also generates the error signal representing the difference between the sensed signal and the estimated response signal. A masking threshold generator receives the sensed signal and the error signal and produces spectral shaping parameters. A shaped signal generator for receives the spectral shaping parameters and produces a test signal which is provided as an input to the control system.

Abstract: The present invention provides a method of developing an acoustic anti-transient-masking transform and an acoustic anti-transient-masking transform system for compensating effects of undesired vibrations impinging an audio component. The present invention also provides a method of compensating an audio signal for effects of undesired vibrations. In one embodiment, the method includes providing an impulse type signal to an undesired vibration compensated version of the audio component and an uncompensated version of the audio component. The method further includes computing a difference impulse response between a first sampled output from the compensated version and a second sampled output from the uncompensated version, and converting the difference impulse response to a signal representing the acoustic anti-transient-masking transform.

Abstract: The invention relates to a method of and an arrangement for damping a wall movement. In the invention, the strength of an electric field between a surface of a wall and an air-permeable mass plate parallel with the surface is controlled to provide a force opposite to the wall-moving force. A sound wave, for instance, may cause a force moving a wall back and forth, which force is cancelled by the opposite force by means of the method and arrangement of the invention, whereby the movement applied to the wall by the sound wave can be stopped.

Abstract: A technique for reducing acoustic noise emitted by a magnetic resonance imaging system includes providing energy dampening elements in the scanner, such as within the gradient coil assembly, between the gradient coil assembly and the primary magnet, and around the outer and inner peripheries of the primary magnet and RF coil. The elements may be formed to conform to the structures of the scanner, and may be tile-like elements which can be fitted to new scanners and retrofitted to existing equipment.

Abstract: An interconnected distributed network of actuator devices for the control of damping vibrations in mechanical structures. The network includes at least two actuators and at least two impedances arranged in parallel with respective actuators of the at least two actuators. A transmission line connects the parallel arrangement of the at least two actuators and the at least two impedances thereby forming a continuous distributed network.

Abstract: A method and system for determining locations in a design of an assembly likely to result in buzz, rattle, squeak (“BSR”), and/or other noise conditions. The invention uses a finite element model to represent a design. BSR effects are predicted based upon analysis performed on multiple design models. Users may engage in real-time “what if” analyses to determine the effects of various design and component changes on noise source characteristics. Additional intelligence may be applied to limit the number of model points subject to evaluation. Displacements, contact velocities, and force responses at selectively identified subsets of interesting points can evaluate noise characteristics. An “as designed” model may evaluate noise source characteristics at the beginning of the life of an assembly. Degraded models can determine the effects of aging and use.

Abstract: Body or structural noise transmitted through a connector such as a strut, that connects a noise source, such as an engine, to an enclosure, such as a passenger cabin or cell of a helicopter, is suppressed by at least one piezoactuator which is excited to counteract any vibrations of the strut caused by body noise so that body noise vibrations are cancelled or at least substantially suppressed. The excitation of the piezoactuator is controlled in closed loop fashion in response to feedback signals from a sensor secured to the connector.

Abstract: An apparatus for suppressing an induced intracranial noise or vibrational signal within a patient's head due to a drilling or cutting medical instrument. The apparatus includes a mechanism for sensing the intracranial vibrational signal induced within the patient's head. The apparatus also includes a mechanism for adaptively generating an intracranial vibrational suppression signal from the intracranial vibrational signal as a function of time. In addition, the apparatus provides a mechanism for applying the intracranial vibrational suppression signal to the patient's head for suppressing the induced intracranial noise or vibrational signal.

Abstract: An adaptive controller is used to adaptively generate vibration cancellation signals driving a controlled device which effects an associated vibration and noise-producing plant. The adaptive controller has multiple control paths to generate the control signal. In a vibration attenuation control path(s), an adaptive control signal is generated by plant compensation and adaptive filtering techniques to cancel vibrations. In a position control, saturation prevention path, the available operational extents of the controlled device are monitored and compensation signals are generated which direct the movement of the controlled device in such a manner as to prevent the controlled device from reaching the extents of control. The control signals from the multiple paths are then combined and transmitted to the controlled device which alters in some fashion the noise and vibration being generated or transmitted by the associated vibrating plant.

Abstract: In a method of suppressing or controlling thermoacoustic vibrations which develop in a combustion system having a burner working in a combustion chamber due to the formation of coherent or vortex structures and a periodic heat release associated therewith, in which method the vibrations are detected in a closed control loop and acoustic vibrations of a certain amplitude and phase are generated as a function of the detected vibrations and induced in the combustion system, improved suppression is achieved in that, within the control loop, the amplitude of the generated acoustic vibrations is selected to be proportional to the amplitude of the detected vibrations.

Abstract: A device generates a directional anti-sound beam by modulating an ultrasonic carrier with a sound canceling signal and exciting an ultrasonic transducer with the modulated signal. When the anti-sound beam is directed at a sound source, the level of sound from the sound source is reduced. A microphone monitors the resultant sound for adjusting the sound canceling signal. An alternate signal may be further modulated upon the anti-sound beam to provide a substitute sound at the sound source.

Abstract: Different parameters are supplied to a noise reduction algorithm based on the detection of different vehicle conditions, thereby allowing the noise reduction algorithm to process audio input differently depending on the corresponding vehicle conditions, such as speed, motor rpm, radio on/off status, window open/closed status, occupancy and position of vehicle seat(s), or any combination thereof. One or more vehicle conditions are detected by the vehicle and communicated to a noise reduction control device that determines the appropriate noise reduction algorithm parameters to use based on the detected vehicle conditions, advantageously with reference to a plurality of stored sets of noise reduction algorithm parameters previously established through a calibration process and stored in memory.

Abstract: An interconnected distributed network of actuator devices for the control of damping vibrations in mechanical structures. The network includes at least two actuators and at least two impedances arranged in parallel with respective actuators of the at least two actuators. A transmission line connects the parallel arrangement of the at least two actuators and the at least two impedances thereby forming a continuous distributed network.

Abstract: An active noise controller includes a duct (2) of a stainless steel having the shape of a pipe and provided with an opening (1) at a first end thereof, and a loudspeaker (3)connected to a second end of the duct (2). The duct (2) is disposed with its opening (1) located at a distance not greater than half the wavelength of a sound produced by a sound source (4) from the sound source (4) so as to face the sound source (4). A sound produced by the vibration of the vibrating member (5) of the loudspeaker (3) travels from the second end of the duct (2) through the duct (2) to the first end of the same, and the sound is radiated toward the sound source (4). The sound radiated through the opening (1) has a frequency substantially equal to that of an unnecessary sound included in the sound produced by the sound source (4), an amplitude substantially equal to that of the unnecessary sound and a phase substantially opposite to that of the unnecessary sound.

Abstract: The method of noise attenuation comprises the steps of generating a noise canceling signal, sensing for an system condition, and ceasing the generation of the noise canceling based upon the system condition. This method is embodied in a system that includes an air induction body, a speaker in proximity to the air induction body, a sensor for sensing a system condition, and a control unit with a noise cancellation feature. The control unit is in communication with both the speaker and the sensor. Based upon the sensed system condition, the control unit may disable the noise cancellation feature.