Abstract: Digital signal processing techniques for automatically reducing audible noise from a sound recording that contains speech. A noise suppression system uses two types of noise estimators, including a more aggressive one and less aggressive one. Decisions are made on how to select or combine their outputs into a usable noise estimate in a different speech and noise conditions. A 2-channel noise estimator is described. Other embodiments are also described and claimed.

Abstract: A multichannel acoustic system (MAS) comprises an arrangement of microphones and loudspeakers and a multichannel acoustic processor (MAP) to together enhance conversational speech between two or more persons in a shared acoustic space such as an automobile. The enhancements are achieved by receiving sound signals substantially originating from relatively near sound sources; filtering the sound signals to cancel at least one echo signal detected for at least one microphone from among the plurality of microphones; filtering the sound signals received by the plurality of microphones to cancel at least one feedback signal detected for at least one microphone from among the plurality of microphones; and reproducing the filtered sound signals for each microphone from among the plurality of microphones on a subset of loudspeakers corresponding that are relatively far from the source microphone.

Abstract: Systems, apparatuses and methods for integrating adaptive noise cancellation (ANC) with communication features in an enclosure, such as an incubator, bed, and the like. Utilizing one or more error and reference microphones, a controller for a noise cancellation portion reduces noise within a quiet area of the enclosure. Voice communications are provided to allow external voice signals to be transmitted to the enclosure with minimized interference with noise processing. Vocal communications from within the enclosure may be processed to determine certain characteristics/features of the vocal communications. Using these characteristics, certain emotive and/or physiological states may be identified.

Abstract: In accordance with systems and methods of this disclosure, a method may include generating a feedforward anti-noise signal component from a result of measuring with the reference microphone countering the effects of ambient audio sounds at an acoustic output of a transducer by filtering an output of the reference microphone, adaptively generating a feedback anti-noise signal component from a result of measuring with an error microphone for countering the effects of ambient audio sounds at the acoustic output of the transducer by adapting a response of a feedback adaptive filter that filters a synthesized reference feedback to minimize the ambient audio sounds in the error microphone signal, wherein the synthesized reference feedback is based on a difference between the error microphone signal and the feedback anti-noise signal component.

Abstract: In accordance with methods and systems of the present disclosure, a processing circuit may implement a feedback filter having a response that generates a feedback anti-noise signal component from a playback corrected error, the playback corrected error based on a difference between an error microphone signal and a secondary path estimate, and wherein the anti-noise signal comprises at least the feedback anti-noise signal component, a secondary path estimate filter configured to model an electro-acoustic path of the source audio signal and have a response that generates a secondary path estimate from the source audio signal, and a secondary coefficient control block that shapes the response of the secondary path estimate adaptive filter in conformity with a source audio signal and the playback corrected error by adapting the response of the secondary path estimate adaptive filter to minimize the playback corrected error.

Abstract: An audio beamformer receives signals from microphones of an array and processes the signals to produce a directional audio signal that emphasizes sound from a selected direction. The beamformer is implemented using weights or other parameters that are calculated to account for effects upon the received audio signals by the surfaces upon which the microphones are positioned.

Abstract: Noises that are to be emitted by an aerial vehicle during operations may be predicted using one or more machine learning systems, algorithms or techniques. Anti-noises having equal or similar intensities and equal but out-of-phase frequencies may be identified and generated based on the predicted noises, thereby reducing or eliminating the net effect of the noises. The machine learning systems, algorithms or techniques used to predict such noises may be trained using emitted sound pressure levels observed during prior operations of aerial vehicles, as well as environmental conditions, operational characteristics of the aerial vehicles or locations of the aerial vehicles during such prior operations. Anti-noises may be identified and generated based on an overall sound profile of the aerial vehicle, or on individual sounds emitted by the aerial vehicle by discrete sources.

Abstract: A personal audio device including multiple output transducers for reproducing different frequency bands of a source audio signal, includes an adaptive noise canceling (ANC) circuit that adaptively generates an anti-noise signal for each of the transducers from at least one microphone signal that measures the ambient audio to generate anti-noise signals. The anti-noise signals are generated by separate adaptive filters such that the anti-noise signals cause substantial cancellation of the ambient audio at their corresponding transducers. The use of separate adaptive filters provides low-latency operation, since a crossover is not needed to split the anti-noise into the appropriate frequency bands. The adaptive filters can be implemented or biased to generate anti-noise only in the frequency band corresponding to the particular adaptive filter. The anti-noise signals are combined with source audio of the appropriate frequency band to provide outputs for the corresponding transducers.

Abstract: An active vibration or noise suppression system is provided that achieves fast convergence of vibration or noise. A sine wave control signal y(n) is constituted by frequency of a vibration or noise source, and an amplitude filter coefficient a(n) and a phase filter coefficient ?(n) as an adaptive filter coefficient. The sine wave control signal y(n) is expressed by a sine wave having an amplitude component and a phase component, and each of an amplitude update term ?a(n+1) and a phase update term ??(n+1) includes a sine wave or cosine wave term having an amplitude component and a phase component. The phase component of the sine wave control signal y(n) is multiplied by a coefficient other than 1, or the phase component of the sine wave or cosine wave term of each of the amplitude update term ?a(n+1) and the phase update term ??(n+1) is multiplied by a coefficient other than 1.

Abstract: An ultrasonic noise cancelation system can include a communication module configured to receive a noise signal detected by a noise detection module, the noise signal representing a noise sound in a listener environment; a noise cancelation module configured to invert the received noise signal thereby creating an inverse noise signal representing an inverse of the noise sound; and a modulator configured to modulate the inverse noise signal onto an ultrasonic carrier to generate an ultrasonic signal.

Abstract: Unlike sound based pressure waves that go everywhere, air turbulence caused by wind is usually a fairly local event. Therefore, in a system that utilizes two or more spatially separated microphones to pick up sound signals (e.g., speech), wind noise picked up by one of the microphones often will not be picked up (or at least not to the same extent) by the other microphone(s). Embodiments of methods and apparatuses that utilize this tact and others to effectively detect and suppress wind noise using multiple microphones that are spatially separated are described.

Abstract: In accordance with methods and systems of the present disclosure, a processing circuit may implement at least one of: a feedback filter having a response that generates at least a portion of an anti-noise component from a playback corrected error, the playback corrected error based on a difference between the error microphone signal and a secondary path estimate; and a feedforward filter having a response that generates at least a portion of the anti-noise signal from a reference microphone signal. The processing circuit may also implement a secondary path estimate filter configured to model an electro-acoustic path of a source audio signal and have a response that generates a secondary path estimate from the source audio signal and a secondary path estimate performance monitor for monitoring performance of the secondary path estimate filter in modeling the electro-acoustic path.

Abstract: From at least a first microphone, first microphone signals are received that represent first sound waves. From at least a second microphone, second microphone signals are received that represent second sound waves. In response to the first microphone signals, first noise in the first sound waves is estimated, and first cancellation signals are output for causing a speaker array to generate first additional sound waves via at least a first acoustic beam for cancelling at least some of the first noise. In response to the second microphone signals, second noise in the second sound waves is estimated, and second cancellation signals are output for causing the speaker array to generate second additional sound waves via at least a second acoustic beam for cancelling at least some of the second noise.

Abstract: An adaptive noise canceller adapts a secondary path modeling response using ambient noise, rather than using another noise source or source audio as a training source. Anti-noise generated from a reference microphone signal using a first adaptive filter is used as the training signal for training the secondary path response. Ambient noise at the error microphone is removed from an error microphone signal, so that only anti-noise remains. A primary path modeling adaptive filter is used to modify the reference microphone signal to generate a source of ambient noise that is correlated with the ambient noise present at the error microphone, which is then subtracted from the error microphone signal to generate the error signal. The primary path modeling adaptive filter is previously adapted by minimizing components of the error microphone signal appearing in an output of the primary path adaptive filter while the anti-noise signal is muted.

Abstract: A full-duplex RF communication system and corresponding methods use digital adaptive filters for interference cancellation. As provided, the techniques allow full-duplex radio frequency communication without frequency-, time-, or code-division multiplexing and without the use of hardware RF cancellers. Such techniques may be useful for wireless communication, such as cellular communication, radio communication, broadcasting, short-range point-to-point communication, wireless sensor networks, and wireless computer networks.

Abstract: A canal phone incorporates a transducer within an isolation sound chamber for reproducing sound from an audio source, and a sound-transmission passageway, or ambient sound port, for allowing ambient sounds to enter the isolation sound chamber. The passageway has inner and outer apertures, one oriented towards the ambient noise environment outside of the listener's ear and the other oriented toward the isolated chamber formed by the space between a loudspeaker diaphragm within the canal phone and the tympanum of the listener's ear. The canal phone has a port blocking switch mechanism that selectively opens or closes the aperture of the passageway that is open to the ambient noise. This switch mechanism may also electrically disconnect the transducer and seal either the outer or the inner end of the passageway in different embodiments of the invention.

Abstract: A personal audio device, such as a wireless telephone, generates an anti-noise signal from an error microphone signal and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. The error microphone is also provided proximate the speaker to provide an error signal indicative of the effectiveness of the noise cancellation. A secondary path estimating adaptive filter is used to estimate the electro-acoustical path from the noise canceling circuit through the transducer so that source audio can be removed from the error signal. Noise bursts are injected intermittently and the adaptation of the secondary path estimating adaptive filter controlled, so that the secondary path estimate can be maintained irrespective of the presence and amplitude of the source audio.

Abstract: An active noise control device detects composite vibration of a vibration transmitting route to which both vibration of a rotating body caused by generation or transmission of drive force of a vehicle and vibration of a wheel generated by contact between the wheel and a road surface are transmitted. A first reference signal for defining a reference waveform of a canceling sound for canceling vibration noise in a vehicle interior is generated based on the composite vibration. The component of the canceling sound for canceling vibration noise of the rotating body is removed from the first reference signal to generate a second reference signal for defining a reference waveform of the canceling sound for canceling vibration noise of the wheel. The canceling sound is outputted based on the second reference signal.

Abstract: There is provided a signal processing device s including a noise cancellation process clock generation unit configured to generate a noise cancellation process clock having a predetermined fixed frequency, a noise canceling unit configured to include a noise canceling filter operating based on the noise cancellation process clock and generating a noise canceling signal having a signal property of canceling an external noise component based on an input audio signal including the external noise component picked up by a microphone, and an addition unit superimposing the noise canceling signal generated by the filter on a digital audio signal, and a sampling rate conversion unit configured to rate-convert the input digital audio signal sampled at a clock in asynchrony with the noise cancellation process clock to a signal at a sampling frequency in synchrony with the noise cancellation process clock and to supply the rate-converted signal to the addition unit.

Abstract: An active noise control system for exhaust systems of a combustion engine operated vehicle comprises an anti-sound control connectable to an engine control of the vehicle and a loudspeaker connected to the control for receiving control signals and designed for generating an anti-sound in a sound generator, fluidically connectable to the exhaust system. In the control, at least two curves are stored in order to cancel airborne sound conducted in the exhaust system through outputting the signal to the loudspeaker. The curves cover different temperature ranges of the exhaust gas, which temperature ranges overlap one another by pairs or directly adjoin one another. The control is furthermore designed to select a curve suitable for a respective temperature of the exhaust gas conducted in the exhaust system from the available curves by means of signals output by the engine control and output signals to the loudspeaker making use of this curve.

Abstract: In an active noise reducing headphone, a signal processor is configured to apply first feedback filters to the feedback signal path, causing the feedback signal path to operate at a first gain level, as a function of frequency, during a first operating mode, and apply second feedback filters to the feedback signal path, causing the feedback signal path to operate at a second gain level less than the first gain level at some frequencies during a second operating mode. The first gain level is a level of gain that results in effective cancellation of sounds transmitted through or around the ear cup and through the user's head, and the second level is a level of gain that is matched to the level of sound of a typical wearer's voice transmitted through the wearer's head when wearing the headphone.

Abstract: An ultrasonic noise cancelation system can include a communication module configured to receive a noise signal detected by a noise detection module, the noise signal representing a noise sound in a listener environment; a noise cancelation module configured to invert the received noise signal thereby creating an inverse noise signal representing an inverse of the noise sound; and a modulator configured to modulate the inverse noise signal onto an ultrasonic carrier to generate an ultrasonic signal.

Abstract: Provided are methods and systems for noise suppression within multiple time-frequency points of spectral representations. A multi-feature cluster tracker is used to track signal and noise sources and to predict signal versus noise dominance at each time-frequency point. Multiple features, such as binaural and monaural features, may be used for these purposes. A Gaussian mixture model (GMM) is developed and, in some embodiments, dynamically updated for distinguishing signal from noise and performing mask-based noise reduction. Each frequency band may use a different GMM or share a GMM with other frequency bands. A GMM may be combined from two models, with one trained to model time-frequency points in which the target dominates and another trained to model time-frequency points in which the noise dominates. Dynamic updates of a GMM may be performed using an expectation-maximization algorithm in an unsupervised fashion.

Abstract: According to an embodiment, an active noise-reduction apparatus includes following elements. The microphone converts a sound including a target sound into an error signal. The control filter generates a control signal in accordance with a control characteristic. The first control effect estimation filter converts the control signal into a first signal in accordance with an estimated secondary path characteristic. The second control effect estimation filter converts the control signal into a second signal in accordance with a processed secondary path characteristic obtained by shortening a delay of the estimated secondary path characteristic. The updating unit updates the control characteristic based on the error signal, the first signal, and the second signal.

Abstract: Embodiments of a system and method for adapting a phase difference-based noise reduction system are generally described herein. In some embodiments, spatial information associated with a first and second audio signal are determined, wherein the first and second audio signals including a target audio inside a beam and noise from outside the beam. A signal-to-noise ratio (SNR) associated with the audio signals is estimated. A mapping of phase differences to gain factors is adapted for determination of attenuation factors for attenuating frequency bins associated with noise outside the beam. Spectral subtraction is performed to remove estimated noise from the single-channel signal based on a weighting that affects frequencies associated with a target signal less. Frequency dependent attenuation factors are applied to attenuate frequency bins outside the beam to produce a target signal having noise reduced.

Abstract: Various embodiments of the invention include systems, computer program products, and related methods for managing power plant acoustics. In various embodiments, a system is disclosed including at least one computing device configured to perform the following: determine a difference between an A-weighted sound decibel (dBA) level and a C-weighted sound decibel (dBC) level (? dBC-dBA) from a power plant system within a sound spectrum; compare the ? dBC-dBA with a predetermined threshold difference for the sound spectrum; and provide instructions to increase the dBA level of a balancing sound in the spectrum proximate the power plant system in response to determining the ? dBC-dBA exceeds the predetermined threshold difference.

Abstract: An audio system has a first channel for receiving a first input signal and driving a first speaker and a second channel for receiving a second input signal and driving a second speaker. A first feedforward circuit couples an input of the second channel circuit to an input of the first channel circuit. A second feedforward circuit couples an input of the first channel circuit to an input of the second channel circuit. Circuit parameters of the first and the second feedforward circuits are determined such that a first detected output signal is zero when the first input signal is non-zero and the second input signal is zero, and a second detected output signal is zero when the second input signal is non-zero and the first input signal is zero. The audio system is configured to operate using the determined circuit parameters for the first and the second feedforward circuits.

Abstract: Systems and methods for controlling adaptivity of noise cancellation are presented. One or more audio signals are received by one or more corresponding microphones. The one or more signals may be decomposed into frequency sub-bands. Noise cancellation consistent with identified adaptation constraints is performed on the one or more audio signals. The one or more audio signals may then be reconstructed from the frequency sub-bands and outputted via an output device.

Abstract: A noise canceling system comprises a microphone generating a captured signal and a sound transducer radiating a sound canceling audio signal in the audio environment. A feedback path from the microphone to the sound transducer includes a non-adaptive canceling filter and a variable gain and receives the captured signal and generates a drive signal for the sound transducer. A gain detector determines a secondary path gain for at least part of a secondary path of a feedback loop. The secondary path may include the microphone, the sound transducer, and the acoustic path therebetween but does not include the non-adaptive canceling filter or the variable gain. A gain controller adjusts the in of the variable gain in response to the secondary path gain. The system use simple gain estimation and control to efficiently compensate for variations in the secondary path to provide improved stability and noise canceling performance.

Abstract: The headset comprises two earpieces each having a transducer for playing back the sound of an audio signal and received in an acoustic cavity defined by a shell having an ear-surrounding cushion. The active noise control comprises, in parallel, a feedforward bandpass filter receiving the signal from an external microphone, a feedback bandpass filter receiving as input an error signal delivered by an internal microphone, and a stabilizer bandpass filter locally increasing the phase of the transfer function of the feedback filter in an instability zone, in particular a waterbed effect zone around 1 kHz. A summing circuit delivers a weighting linear combination of the signal delivered by these filters together with the audio signal to be played back. Control is non-adaptive, with the parameters of the filters being static.

Abstract: Techniques associated with an acoustic vibration sensor are described, including a first detector that receives a first signal and a second detector that receives a second signal and a third signal, wherein the first signal comprises a skin surface microphone signal, a static equalization filter coupled to the first detector and configured to generate an equalized first signal, a voice activity detector coupled to the first detector, and a wind detector coupled to the second detector, the wind detector configured to correlate the second signal and the third signal and to derive from the correlation a plurality of wind metrics associated with a wind noise, the wind detector is further configured to determine a magnitude associated with the wind noise, to determine whether to suspend an activity of the system, and to determine a duration of time that the magnitude associated with the wind noise exceeds a threshold.

Abstract: A Noise Cancellation Process for enclosed cabins is disclosed. According to one embodiment, an input audio source corresponding to sound received from multiple microphones situated equidistantly in both directions in a two dimensional plane, is converted to a digital signal via an analog to digital (A/D) convertor. The A/D converted audio is analyzed for content to identify ambient noise. The frequency, amplitude and phase of the identified ambient noise is subsequently determined. A Noise correction sound wave is generated with negative phase of that corresponding to the identified ambient noise. The noise correction sound wave is added to the identified noise to create a noise corrected sound.

Abstract: In an active muffler having improved response characteristics, a speaker section includes a diaphragm adapted to generate sound, a voice coil for driving the diaphragm, and a distance sensor to detect the movement of the diaphragm. A light generated by the LED is reflected by the diaphragm, the reflected light is detected by a phototransistor to thereby measure the distance to the diaphragm, so that the movement of the diaphragm is detected. Noise is detected by a microphone, and a signal having opposite phase to that of the noise is generated by an opposite-phase generating section. The difference between the opposite-phase signal and the signal of the distance to the speaker from the distance sensor is calculated and inputted to a PID control section. Such a difference indicates the delay of the speaker movement. Feedback control is performed in a direction in which the difference is canceled out.

Abstract: A personal audio device, such as a wireless telephone, includes an adaptive noise canceling (ANC) circuit that adaptively generates an anti-noise signal from a reference microphone signal and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. An error microphone is also provided proximate the speaker to estimate an electro-acoustical path from the noise canceling circuit through the transducer. A processing circuit determines a degree of coupling between the user's ear and the transducer and adjusts the adaptive cancellation of the ambient sounds to prevent erroneous and possibly disruptive generation of the anti-noise signal if the degree of coupling lies either below or above a range of normal operating ear contact pressure.

Abstract: A system for actively reducing noise at a listening point, includes an earphone housing, a transmitting transducer, a receiving transducer and a controller. The transmitting transducer converts a first electric signal into a first acoustic signal, and radiates the first acoustic signal along a first acoustic path having a first transfer characteristic and along a second acoustic path having a second transfer characteristic. The receiving transducer converts the first acoustic signal and ambient noise into a second electrical signal. The controller compensates for the ambient noise by providing a noise reducing electrical signal to the transmitting transducer. The noise reducing electrical signal is derived from a filtered electrical signal that is provided by filtering the second electrical signal with a third transfer characteristic. The second and the third transfer characteristics together model the first transfer characteristic.

Abstract: In accordance with the present disclosure, an integrated circuit for implementing at least a portion of a personal audio device may include an output and a processing circuit. The output may provide an output signal to a transducer including both a source audio signal for playback to a listener and an anti-noise signal for countering the effect of ambient audio sounds in an acoustic output of the transducer. The processing circuit may implement an adaptive noise cancellation system that generates the anti-noise signal to reduce the presence of the ambient audio sounds heard by the listener by adapting, based on a presence of the source audio signal, a response of the adaptive noise cancellation system to minimize the ambient audio sounds at the acoustic output of the transducer, wherein the adaptive noise cancellation system is configured to adapt both in the presence and the absence of the source audio signal.

Abstract: In accordance with methods and systems of the present disclosure, a processing circuit may implement a feedback filter having a response that generates a feedback anti-noise signal component from a playback corrected error, the playback corrected error based on a difference between an error microphone signal and a secondary path estimate, and wherein the anti-noise signal comprises at least the feedback anti-noise signal component, a secondary path estimate filter configured to model an electro-acoustic path of the source audio signal and have a response that generates a secondary path estimate from the source audio signal, and a secondary coefficient control block that shapes the response of the secondary path estimate adaptive filter in conformity with a source audio signal and the playback corrected error by adapting the response of the secondary path estimate adaptive filter to minimize the playback corrected error.

Abstract: An active noise control (ANC) system may be implemented to both sides of a fan, such that both directions of the noise emitting are treated to reduce the overall noise. The impact on airflow is minimal, and the technique is very effective in a broad range of low frequencies. Passive sound-absorbing materials may be included for attenuation of high frequencies. The resulting quiet fan produces a low level of noise compared to any other device based on fan, which produces the same capacity of airflow. The quiet fan may be incorporated in any mechanical system which requires airflow induction such as: computers, air conditioners, machines, and more.

Abstract: A loudspeaker system has a front loudspeaker enclosure (30) having at least one first loudspeaker (20) and a rear loudspeaker enclosure (50) having at least one second loudspeaker (60). The rear loudspeaker enclosure (50) is in the form of a bandpass enclosure.

Abstract: Broadly speaking, the embodiments disclosed herein describe an apparatus, system, and method for managing the effects of TDMA noise emitted by a communication device on an audio circuit.

Abstract: A method of controlling a noise cancellation system, for use in an audio device, comprises: generating an ambient noise signal representative of ambient noise; filtering and applying gain to the ambient noise signal to generate a noise cancellation signal; passing the noise cancellation signal to a speaker; and generating an error signal from an error microphone, wherein the gain applied to the ambient noise signal is controlled based on the error signal, and the method further comprises: determining from the error signal whether the audio device is in an off-ear position, and controlling the noise cancellation system based on said determination as to whether the audio device is in the off-ear position.

Abstract: In an aspect, in general, a feedback based active noise reduction system is configured to detect actual or potential instability by detecting characteristics of the system related to potential or actual unstable behavior (e.g., oscillation) and adapt system characteristics to mitigate such instability.

Abstract: In one aspect, in general, an active noise reduction system detects actual or potential instability by detecting characteristics of the system related to potential or actual unstable behavior (e.g., oscillation) and adapts system characteristics to mitigate such instability. In some examples, the system adapts to variation in characteristics of an acoustic component of a feedback path that has or may induce unstable behavior to improve a user's acoustic experience.

Abstract: A system utilizing two pairs of microphones for noise suppression. Primary and secondary microphones may be positioned closely spaced to each other to provide acoustic signals used to achieve noise cancellation/suppression. An additional, tertiary microphone may be spaced with respect to either the primary microphone or the secondary microphone in a spread-microphone configuration for deriving level cues from audio signals provided by the tertiary and the primary or secondary microphone. The level cues are expressed via a level difference used to determine one or more cluster tracking control signal(s). The level difference-based cluster tracking signals are used to control adaptation of noise suppression. A noise cancelled primary acoustic signal and level difference-based cluster tracking control signals are used during post filtering to adaptively generate a mask to be applied to a speech estimate signal.

Abstract: Apparatus for reproduction of stereo sound from a two channel signal, having one or more first transducers (3a, 3b) for reproducing a signal comprising one of or the sum of the two channels, and one or more second transducers (5) for reproducing a signal comprising the difference between the two channels. The apparatus is arranged such that the signal generated by the one or more first transducers (3a, 3b) is transmitted from an output plane in a direction substantially orthogonal to the output plane. The apparatus also has a duct (6) associated with the one or more second transducers (5) and is arranged to conduct the signal generated by the one or more second transducers (5) such that it is transmitted along a direction substantially parallel to the output plane from a point spaced from the plane in the direction in which the signal generated by the one or more first transducers (3a, 3b) is transmitted.

Abstract: This document discusses, among other things, systems and methods for active noise cancellation. One example system includes a digital ANC circuit configured to receive first audio information from a first microphone and to produce an a digital anti-noise signal configured to attenuate noise sensed by the first microphone; an analog ANC circuit configured to receive second audio information from a second microphone and to produce an analog anti-noise signal configured to attenuate noise sensed by the second microphone; and wherein the system is configured to receive an intended audio signal and to provide an output signal for a speaker using the intended audio signal, the analog anti-noise signal, and the digital anti-noise signal.

Abstract: A noise cancellation system is provided, for generating a noise cancellation signal to be added to a wanted signal to mitigate the effects of ambient noise. The system comprises: an input, for receiving an input signal representing ambient noise; a detector, for detecting a magnitude of said input signal; and a voice activity detector, for determining voiceless periods when said input signal does not contain a signal representing a voice. The detector is adapted to detect the magnitude of said input signal during said voiceless periods, and the system is adapted to operate in a first mode when said input signal is above a threshold value, and a second mode when said input signal is below the threshold value. The first mode comprises generating a noise cancellation signal with a first magnitude for at least partially cancelling the ambient noise. The second mode comprises generating a noise cancellation signal with a second magnitude that is less than the first magnitude.

Abstract: An adaptive active noise cancellation apparatus performs a filtering operation in a first digital domain and performs adaptation of the filtering operation in a second digital domain.

Abstract: An active noise cancellation controller for performing noise attenuation in a system over a predetermined frequency rang. The controller comprises several components: a first input for a reference signal indicative of a noise level; a second input for receiving an error signal indicative of a remnant noise level; an output for providing a noise cancellation signal; a fixed feedback controller for processing the error signal; a fixed feed-forward controller for processing the reference signal; and an adaptive feed-forward controller having a digital adaptive finite impulse response filter arranged for operation on the reference signal the error signal.

Abstract: A method and apparatus for providing simultaneous enhancement of transmission loss and absorption coefficient using activated cavities is presented. A layer of material is provided, and a backing plate having a plurality of cavities on the top surface of said backing plate, is disposed adjacent a top surface of said layer of material. A screen is disposed along the top surface of said cavities on said backing plate and at least one cavity includes an actuator disposed within the cavity and a control system receiving a signal from the microphone and receiving a signal from the accelerometer and providing a drive signal to the actuator to provide an acoustic output to provide simultaneous insertion loss and absorption which serves to minimize a linear combination of the signal from the microphone and the signal from the accelerometer.