An active noise cancellation (ANC) system may include an adaptive filter divergence detector for detecting divergence of the one or more controllable filters as they adapt, based on dynamically adapted thresholds. Upon detection of a controllable filter divergence, the ANC system may be deactivated, or certain speakers may be muted. Alternatively, the ANC system may modify the diverged controllable filters to restore proper operation of the noise cancelling system.

An electronic device according to an embodiment includes a speaker capable of outputting a sound wave, a sensor capable of acquiring an optical signal related to blood flow at a measured part of a user, and a controller configured to measure blood flow information of the measured part based on the optical signal. The controller estimates a sleep state of the user based on the blood flow information and controls, based on the sleep state, a sound wave outputted from the speaker.

A noise-cancellation system includes a noise-cancellation filter in communication with at least one speaker, the noise-cancellation filter generating a noise-cancellation signal that, when actuated by the at least one speaker, cancels noise within at least one cancellation zone; and an amplifier disposed between the noise-cancellation filter and the speaker, the amplifier applying a first scaling gain to the noise-cancellation signal and outputting an scaled noise-cancellation signal, the scaled noise-cancellation signal being a linear reduction of the noise-cancellation signal when the first scaling gain is less than unity, wherein the first scaling gain is set to less than unity in response to a signal representative of the noise-cancellation signal exceeding a threshold.

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.

This document describes a method that includes receiving a driver signal for an acoustic transducer of an acoustic device. The method also includes receiving a signal from a microphone of the acoustic device, and, processing the driver signal through a filter to provide a reference signal. The filter has a transfer function associated with a condition of the acoustic device. The method also includes comparing the signal to the reference signal to determine whether the signal has a threshold similarity to the reference signal, and, indicating the condition of the acoustic device in respond to the determined threshold similarity.

A road noise-cancellation system, comprising: an actuator disposed in a vehicle cabin; a controller comprising a processor and non-volatile memory, the controller being programmed to: generate a noise-cancellation signal with a noise-cancellation filter including a first plurality of coefficients, the noise-cancellation signal being based on the first plurality of coefficients, the noise-cancellation signal being transduced by the actuator to generate a noise-cancellation audio signal based on the noise-cancellation signal, the noise-cancellation audio signal destructively interfering with an undesired noise in a noise-cancellation zone; adjust the first plurality of coefficients of the noise-cancellation filter based on one or more input signals to provide a second plurality of coefficients; store the second plurality of coefficients in the non-volatile memory during a shutdown sequence or at the end of an interval; and restore the second plurality of coefficients from non-volatile memory to the noise-cancellation filter after (i) startup or (ii) determining that a third plurality of coefficients, provided by a second adjustment, are divergent or unstable.

An active noise cancellation (ANC) system may include provisions for validating the accuracy of a modeled transfer characteristic stored in secondary path filters, which provides an estimate of the secondary path (i.e., the transfer function between a speaker and an error microphone). Using estimated anti-noise or music signals to adjust an error signal from the error microphone, a signal analysis controller may detect ANC instability or noise boosting. Such noise boosting may indicate the stored transfer characteristic in the secondary path filter does not accurately represent the actual secondary path. According, upon detection of noise boosting, the stored transfer characteristic of the secondary path filters may be modified.

An active road noise control method in an active road noise controller disposed in a vehicle may include diagnosing whether a plurality of microphones connected in a daisy chain has failed, receiving a data frame from the plurality of microphones, identifying normal information related to information included in the data frame based on a result of diagnosis, generating a digital noise control signal using the identified normal information, and transmitting the generated digital noise control signal to an external amplifier.

An active Noise Reduction (ANR) device includes a plurality of inputs, a plurality of signal processing resources, an output for driving an earphone driver, a programmable switch arrangement capable of assigning any of the plurality of inputs to any of the plurality of signal processing resources, and a controller for programming the programmable switch arrangement in order to assign each of at least a subset of the plurality of inputs to a different one of the signal processing resources. The ANR device is dynamically configurable to vary which of the signal processing resources are selected to contribute to the output.

A system and method for disabling adaptation in an adaptive feedforward control system at low speeds. The method includes generating a noise signal representative of undesired noise detected by a noise sensor of a vehicle and generating a noise-cancellation signal via a controller within the vehicle. Residual noise resulting from the combination of the acoustic energy of the noise-cancellation signal and the undesired noise is detected by a reference sensor, which generates an error signal based on the residual noise. The error signal and a speed signal from a speed sensor on the vehicle are transmitted to an adaptive processing module for the generation of a filter update signal. The adaptive processing module selectively permits or prevents the filter update signal to adapt filter coefficients of a filter when the speed signal is within a set of conditions.