Cirrus Logic Inc.

Cirrus Logic International Semiconductor Limited

Dayong Zhou

Yang Lu

Jeffrey Donald Alderson

Jon David Hendrix

Antonio John Miller

Ning Li

Chin Huang Yong

Ali Abdollahzadeh Milani

Gautham Devendra Kamath

John L Melanson

Nitin Kwatra

Brad L Zwernemann

Eric Jerome King

Eric Lindemann

Jason William Lawrence

Emmanuel A Marchais

Dana John Taipale

Carl Lennart Ståhl

Ryan A Hellman

Kaichow Lau

Robert George Kratsas

Jens-Peter B Axelsson

Sang-Ik Terry Cho

Robert G Kratsas

Milani Ali Abdollahzadeh

Circuitry for acoustic crosstalk cancellation between first and second acoustic signals, the circuitry comprising: crosstalk cancellation circuitry configured to: receive a first audio signal and, based on the received first audio signal, generate a first crosstalk cancellation signal; receive a second audio signal and, based on the received second audio signal, generate a second crosstalk cancellation signal; combine the first crosstalk cancellation signal with a signal indicative of the second audio signal to generate a first crosstalk cancellation circuitry output signal; and combine the second crosstalk cancellation signal with a signal indicative of the first audio signal to generate a second crosstalk cancellation circuitry output signal; and output stage circuitry configured to: receive the first crosstalk cancellation circuitry output signal and, based on the received first crosstalk cancellation circuitry, generate a first drive signal for driving a first speaker to generate the first acoustic signal; and receive the second crosstalk cancellation circuitry output signal and, based on the received second crosstalk cancellation circuitry, generate a second drive signal for driving a second speaker to generate the second acoustic signal, wherein a parameter of the crosstalk cancellation circuitry is variable based on one or more of: a position of a user of a host device incorporating the circuitry with respect to the host device; a volume setting of the host device; a level of the first and/or second crosstalk cancellation signal; and an operational parameter of the output stage circuitry.

Acoustic crosstalk cancellation

The overall performance of an ANC system may be improved by configuring the ANC system to perform adaption in the frequency domain. The ANC systems may be configured to update an algorithm of an adaptive filter based, at least in part, on the first input signal, the second input signal, and a feedback signal that is based on an output of the adaptive filter. Updating may include changing parameters of the algorithm based on a SDR based, at least in part, on the first input signal. Updating may also include normalizing a step size and processing at least full band information for the input signal in a frequency domain to generate coefficient values for the algorithm. Updating may also include applying a frequency domain magnitude constraint on adaptive filter coefficients.

SDR-based adaptive noise cancellation (ANC) system

A method of obtaining a directional microphone signal, the method comprising: receiving first and second microphone signals from first and second microphones separated by a distance; obtaining a combined microphone signal based on one or more of the first and second microphone signals; obtaining a difference microphone signal by subtracting the second microphone signal from the first microphone signal; obtaining a transformed combined microphone signal by applying a Hilbert transform to the combined microphone signal; combining the transformed combined microphone signal with the difference microphone signal to obtain the directional microphone signal.

Apparatus and method for obtaining directional audio signals

An integrated circuit for implementing at least a portion of a personal audio device may include a processing circuit to implement an adaptive filter having a response that generates an anti-noise signal to reduce the presence of the ambient audio sounds at an error microphone, implement a coefficient control block that shapes the response of the adaptive filter in conformity with the error microphone signal by computing coefficients that determine the response of the adaptive filter to minimize the ambient audio sounds at the error microphone, and responsive to detecting a condition that triggers a reset of the adaptive filter, increment the coefficients in a plurality of steps from initial values of the coefficients at a time of triggering the reset to final values of the coefficients at a conclusion of the reset.

Gradual reset of filter coefficients in an adaptive noise cancellation system

A method for determining a direct current impedance of a transducer may include receiving an input signal indicative of an electrical power consumed by the transducer and calculating, by a thermal model of the transducer, the direct current impedance based on the electrical power.

Thermal model of transducer for thermal protection and resistance estimation

An adaptive filter converts time domain samples of an input signal into frequency domain signals, dynamically adjusts a stability conditional number based on the frequency domain signals, and uses the dynamically adjusted stability conditional number to control step size normalization during adaptation of frequency domain coefficients of the adaptive filter. The stability control number may be global to a range of frequency bins based on a peak magnitude of the input signal and/or may be frequency bin-specific stability control numbers based on corresponding frequency bin-specific error signal magnitudes. The adaptive filter also dynamically adjusts a noise floor based on the frequency domain input signals and refrains from updating frequency domain coefficients when a magnitude of the frequency domain input signal associated with a frequency bin is greater than the dynamically adjusted noise floor.

Input signal-based frequency domain adaptive filter stability control

An adaptive filter includes a frequency domain adaptation block that analyzes a statistic of coefficient movement in the frequency domain. The adaption block adjusts, in the frequency domain, a parameter (step size or leakage factor) that affects speed of convergence of the adaptive filter based on the analyzed statistic of filter coefficient movement. The filter includes an associated coefficient, statistic of coefficient movement, and parameter for each frequency bin. The coefficients may be complex numbers, and separate real and imaginary statistics and parameters are maintained. The statistic may be direction counts of the filter coefficient movement. The step size may be adjusted to a predetermined minimum value when the current direction of movement of the filter coefficient is different than the predominant direction and otherwise the step size is adjusted approximately proportionally to an amount of predominance by a value based on a direction count of the filter coefficient movement.

Frequency domain adaptation with dynamic step size adjustment based on analysis of statistic of adaptive filter coefficient movement

An adaptive filter calculates frequency domain coefficients and in the frequency domain dynamically adjusts a leakage/step size parameter that controls adaptation of the adaptive filter based on the calculated frequency domain coefficients (e.g., based on a peak magnitude of the coefficients among frequency bins or on the magnitude of the coefficient of the corresponding frequency bin). The adaptive filter calculates the coefficients based on frequency domain input and error signals, dynamically adjusts a frequency domain coefficient magnitude limit parameter based on the calculated frequency domain coefficients (e.g., approximately proportionally to a peak magnitude of the coefficients among frequency bins) and uses the dynamically adjusted frequency domain coefficient magnitude limit parameter to limit a magnitude of the calculated frequency domain coefficients. The limit may be engaged above a frequency bin based on the peak magnitude frequency bin. An ANC system may employ the filter.

Frequency domain coefficient-based dynamic adaptation control of adaptive filter

The handling of disturbances to audio signals may be improved with an adaptive noise cancellation (ANC) system that performs frequency-domain adaption. The ANC systems may be configured to determine if a disturbance is present at a first frequency in the second input signal received from the reference microphone. The ANC systems may update an algorithm of an adaptive filter based, at least in part, on the first input signal, the second input signal, and a feedback signal that is based on an output of the adaptive filter by changing parameters of the algorithm such that the adaptive filter adapts around the first frequency differently than other frequencies when the disturbance is present.

Frequency-domain adaptive noise cancellation system

The handling of disturbances to audio signals may be improved with an adaptive noise cancellation (ANC) system that performs tone suppression and howl suppression in a collaborative manner. Such ANC systems may be configured to detect a first tone in an input signal at a first tone frequency and extract the detected first tone from the input signal. The ANC systems may also be configured to adaptively filter the extracted first tone to generate a second tone that has a magnitude that is approximately equal to a magnitude of the extracted first tone and a phase that is approximately opposite the phase of the extracted first tone. The ANC systems may be further configured to add the second tone to an intermediate signal that is based, at least in part, on the input signal to generate the output signal.

Tone and howl suppression in an ANC system

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.

Systems and methods for multi-mode adaptive noise cancellation for audio headsets

In accordance with the present disclosure, an adaptive noise cancellation system may include a controller. The controller may be configured to determine a degree of convergence of an adaptive coefficient control block for controlling an adaptive response of the adaptive noise cancellation system. The controller may enable adaptation of the adaptive coefficient control block if the degree of convergence of the adaptive response is below a particular threshold and disable adaptation of the adaptive coefficient control block if the degree of convergence of the adaptive response is above a particular threshold, such that when the adaptive noise cancellation system is adequately converged, the adaptive noise cancellation system may conserve power by disabling one or more of its components.

Systems and methods for selectively enabling and disabling adaptation of an adaptive noise cancellation system

A controller for an adaptive noise canceling (ANC) system simplifies the design of a stable control response by making the ANC gain of the system independent of a secondary path extending from a transducer of the ANC system to a sensor of the ANC system that measures the ambient noise. The controller includes a fixed filter having a predetermined fixed response, and a variable filter coupled together. The variable response filter compensates for variations of a transfer function of a secondary path that includes at least a path from a transducer of the ANC system to a sensor of the ANC system, so that the ANC gain is independent of the variations in the transfer function of the secondary path.

Feedback adaptive noise cancellation (ANC) controller and method having a feedback response partially provided by a fixed-response filter

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 cancelation 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.

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Austin, TX, United States of America

Dayong Zhou