Cirrus Logic Inc.

Other

State of Oregon

Ning Li

Dayong Zhou

Yang Lu

Antonio John Miller

Jeffrey Donald Alderson

Ziyan Zou

John L Melanson

Jon David Hendrix

Anthony Stephen Doy

Ali Abdollahzadeh Milani

Kaichow Lau

George E Hardy

Larry S Daley

Aleksey Sergeyevich Khenkin

Jie Su

Carl Lennart Ståhl

Vadim A Konradi

Nitin Kwatra

Hamid Sepehr

Marco A Janko

Michael Kurek

Aaron Treptow

Doug Olsen

Mohamed Sabet

Ronald Coapstick

Gerald E Edwards

Peter Foskey

Ben Leslie

Teja Buddha

A method of controlling a vibrational transducer, the method comprising: tracking a temperature metric of the vibrational transducer; and controlling a drive signal for the vibrational transducer, where the drive signal is limited to a value to protect the vibrational transducer from over excursion, and where said value is a function of the tracked temperature metric.

Vibrational transducer control

A method for detecting wind noise incident on a single microphone may include receiving an audio signal indicative of sound incident on the single microphone, dividing the audio signal into a plurality of audio frames, and determining whether wind noise is incident on the single microphone based on a combination of a correlation metric between successive audio frames of the plurality of audio frames and a power ratio difference between a first power ratio and a second power ratio. The first power ratio may equal an amount of power present in a first frequency range of the audio signal to a total amount of power present in the audio signal across all frequencies. The second power ratio may equal an amount of power present in a second frequency range of the audio signal to the total amount of power present in the audio signal across all frequencies.

Single-microphone wind detection for audio device

Methods, systems, circuits and computer program products provide an output signal to drive an electromechanical transducer that selectively contains a cooling component when a thermal limit of a voice coil of the electromechanical transducer is exceeded and which air-cools the transducer by convection. An indication of a temperature of a voice coil of the electromechanical transducer is determined and compared with a thermal limit of the transducer. If the thermal limit of the transducer is exceeded by the indication of the temperature of the voice coil, the cooling component is introduced to the output signal that drives the transducer. The cooling component is a signal having a frequency within a low-frequency resonance portion of the response of the electromechanical transducer, so that additional air convection is caused at the transducer to remove heat from the voice coil due to the cooling component of the output signal.

Transducer cooling by introduction of a cooling component in the transducer input signal

An audio output system for providing an output signal to a micro-speaker provides energy reduction and thermal protection by removing components of an input signal from which the output signal is generated, so that the audio power output system does not expend power reproducing portions of the audio information that would not be perceived by a listener. The micro-speaker has a resonant frequency such that substantial content of the audio information lies below the resonant frequency. A processing subsystem receives the audio information and generates the output signal by filtering the audio information with a response simulating the micro-speaker and an acoustic path to the listener, and comparing the filtered audio information with a frequency-dependent threshold of hearing. The processing subsystem then removes portions of the audio information that have an amplitude below the frequency-dependent threshold of hearing.

Micro-speaker audio power reproduction system and method with reduced energy use and thermal protection using micro-speaker electro-acoustic response and human hearing thresholds

A method for calibrating an ANC-enabled portable audio device having microphones plays continuously a calibration sound by a calibrated speaker of a test station separate from the device. For each microphone of all the microphones, a microphone calibration value is computed using a comparison of a predetermined level and a measured level of an audio signal transduced by the microphone in response to the continuously-played calibration sound. The calibration is done without using a microphone of the test station. A processing element of the device may be programmed to make the comparison and computation. The processing element also causes a speaker of the device to generate a second calibration sound, measures a second level while the computed calibration value is applied to one of microphones (e.g., error microphone), and computes a calibration value for the device speaker using a comparison of a predetermined level and the second level.

System and method for calibrating and testing an active noise cancellation (ANC) system

Embodiments described herein relate to methods and apparatus for limiting the excursion of a transducer. The method comprises receiving a transducer signal; and limiting the transducer signal or a signal derived therefrom to generate a limited transducer signal for input into the transducer such that an electrical response caused by the limited transducer signal in an electrical model of the transducer would be less than a threshold electrical response, wherein the threshold electrical response has been determined by: inputting a stimulus input signal into the electrical model of the transducer, wherein the stimulus input signal is designed to cause the transducer to reach a maximum excursion; and determining the threshold electrical response as a maximum of the electrical response caused by the stimulus input signal in the electrical model of the transducer.

Methods and apparatus for limiting the excursion of a transducer

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

A processing circuit may include: (i) an adaptive filter having a response that generates an anti-noise signal from a reference microphone signal, wherein the response is shaped in conformity with the reference microphone signal and a playback corrected error, and wherein the playback corrected error is based on a difference between an error microphone signal and a secondary path estimate; (ii) a secondary path estimate filter configured to model an electro-acoustic path of a source audio signal and having a response that generates a secondary path estimate from the source audio signal; (iii) a secondary coefficient control block that shapes the response of the secondary path estimate filter in conformity with the source audio signal and the playback corrected error by adapting the response of the secondary path estimate filter to minimize the playback corrected error; and (iv) a noise injection portion for injecting a noise signal into the source audio signal, wherein the noise signal is shaped based on the playback corrected error.

Systems and methods for adaptive noise cancellation by adaptively shaping internal white noise to train a secondary path

In accordance with systems and methods of the present disclosure, an adaptive noise cancellation system may include an alignment filter configured to correct misalignment of a reference microphone signal and an error microphone signal by generating a misalignment correction signal.

Hybrid adaptive noise cancellation system with filtered error microphone signal

A method for cancelling ambient audio sounds in the proximity of a transducer may include receiving an error microphone signal indicative of the output of the transducer and ambient audio sounds at the transducer. The method may also include generating an anti-noise signal for countering the effects of ambient audio sounds at an acoustic output of the transducer, wherein generating the anti-noise signal comprises applying a feedback filter having a response that generates a feedback anti-noise signal based on the error microphone signal and applying a variable gain element in series with the feedback filter. The method may further include monitoring whether an ambient audio event is occurring that could cause the feedback filter to generate an undesirable component in the anti-noise signal and controlling the gain of the variable gain element to reduce the undesirable component.

Systems and methods for performance and stability control for feedback adaptive noise cancellation

A personal audio device 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 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 is injected so that the adaptation of the secondary path estimating adaptive filter can be maintained, irrespective of the presence and amplitude of the source audio. The noise is shaped by a noise shaping filter that has a response controlled in conformity with at least one parameter of the secondary path response.

Frequency-shaped noise-based adaptation of secondary path adaptive response in noise-canceling personal audio devices

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.

Systems and methods for adaptive noise cancellation including secondary path estimate monitoring

Techniques for estimating adaptive noise canceling (ANC) performance in a personal audio device, such as a wireless telephone, provide robustness of operation by triggering corrective action when ANC performance is low, and/or by saving a state of the ANC system when ANC performance is high. An anti-noise signal is generated from a reference microphone signal and is provided to an output transducer along with program audio. A measure of ANC gain is determined by computing a ratio of a first indication of magnitude of an error microphone signal that provides a measure of the ambient sounds and program audio heard by the listener including the effects of the anti-noise, to a second indication of magnitude of the error microphone signal without the effects of the anti-noise. The ratio can be determined for different frequency bands in order to determine whether particular adaptive filters are trained properly.

Adaptive-noise canceling (ANC) effectiveness estimation and correction in a personal audio device

In accordance with method and systems of the present disclosure, a processing circuit may implement an adaptive filter having a response that generates the anti-noise signal from the reference microphone signal to reduce the presence of the ambient audio sounds heard by the listener, a coefficient control block that shapes the response of the adaptive filter in conformity with the error microphone signal and the reference microphone signal by adapting the response of the adaptive filter to minimize the ambient audio sounds in the error microphone signal, and a coefficient bias control block which biases coefficients of the coefficient control block towards zero in a range of frequencies outside of a frequency response of the source audio signal.

Systems and methods for adaptive noise cancellation including dynamic bias of coefficients of an adaptive noise cancellation system

An imaging fluorometer is described comprising a source of electromagnetic radiation, optical components to direct the radiation, excitation and emission filters, and an imaging device. The fluorometer is used to obtain images of the fluorescence emitted by illuminated arrays of photosynthetic components, such as those found in leaves. These fluorescence images, in turn, are used to construct an image of the photosynthetic efficiency of the array. Because efficiency in plants depends on the physiological state of the leaf, the fluorometer affords a method for the sensitive and rapid characterization of freeze damage, herbicide damage, and disease damage to plants. Moreover, the fluorometer may be used in robotic applications, as well as for remote sensing from a location distant from the plant.

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Cedar Park, TX, United States of America

Ning Li