A method performed by an audio output device is provided for detecting instabilities and taking mitigating actions. Specifically, an A-weighted dBA level of a raw feedback signal exceeding a threshold level trigger, at least, muting the driver. The described methods apply to detecting instabilities across a broad frequency spectrum.

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.

A noise control system comprises a feedforward module, a feedback module, an error pre-processing module, and a signal integrating module. The feedforward module is configured to receive a reference signal and output a feedforward anti-noise signal by performing feedforward processing to the reference signal. The feedback module is configured to receive an error signal and output a feedback anti-noise signal by performing feedback processing to the error signal. The error pre-processing module is configured to receive the error signal and output a first pre-processing signal to the feedforward module and a second pre-processing signal to the feedback module. The signal integrating module is configured to output an integrated anti-noise signal integrated from the feedforward anti-noise signal and the feedback anti-noise signal. Wherein the first pre-processing signal corresponds to the first part of the error signal which belongs to the first frequency region; the second pre-processing signal corresponds to the second part of the error signal which belongs to the second frequency region.

An active noise control device controls a speaker so as to output a canceling sound for canceling noise transmitted from a vibration source. The active noise control device includes a control signal generating unit configured to perform signal processing on a basic signal corresponding to a predetermined frequency by a feedback filter and a extraction filter, which is an adaptive notch filter, to generate a control signal that control the speaker, a secondary path filter updating unit configured to update sequentially and adaptively a secondary path filter, and a feedback filter setting unit configured to set the feedback filter based on the secondary path filter.

A sound output device according to an embodiment includes: an acoustic path (70) and a microphone (100b). The acoustic path connects a first space (54b) formed on a front surface of a driver unit (106) and the outside of a housing (50b) including the driver unit separately from a second space (55b) formed on a back surface of the driver unit. The microphone is disposed in the vicinity of an opening where the acoustic path is connected to the outside of the housing.

An active noise reduction device includes: an adaptive filter that generates a cancelling signal by applying an adaptive filter to a reference signal that has a correlation with noise in a space in an automobile, the cancelling signal being used to output a cancelling sound for reducing the noise; and a filter coefficient updater that calculates a coefficient of the adaptive filter based on a predetermined update equation. At a first timing at which the output of the cancelling sound is started, the filter coefficient updater uses a first coefficient as an initial value of the update equation, the first coefficient being the coefficient of the adaptive filter calculated by the filter coefficient updater at a second timing that is prior to the first timing.

An active noise control device includes a determination unit configured to determine whether an abnormality has occurred in an acceleration sensor based on a direct-current component of a reference signal acquired by the acceleration sensor attached to a vehicle, and a control unit configured to, when the determination unit determines that an abnormality has occurred in any of a plurality of the acceleration sensors, stop generation of the control signal based on the reference signal acquired by the acceleration sensor that has been determined to have the abnormality, and stop updating a filter coefficient of an adaptive filter configured to perform the filtering process on the reference signal acquired by the acceleration sensor that has been determined to have no abnormality.

A vibration cancellation method is a vibration cancellation method for canceling vibration arriving at a seat from outside of the seat, the vibration being transmitted to a user seated in the seat. The method includes canceling, by a vibration cancellation unit (4), a vibration by outputting a cancellation signal from a position close to a position where user's head is placed when a user is seated, the cancellation signal being obtained based on a reference signal and an error signal. The reference signal is obtained by a vibration sensor (2) disposed in a position close to a vibration source outside the seat in the seat, and the error signal is obtained by an error vibration sensor (3) disposed in the position close to the position where user's head is placed when the user is seated in the seat.

An echo filtering method, an electronic device, a computer-readable storage medium, and an echo filtering apparatus are disclosed. The electronic device includes M microphones and N speakers. M and N are integers greater than 1. The method includes: obtaining N speaker signals corresponding to the N speakers (302); obtaining M microphone signals corresponding to the M microphones (304); and performing at least direct sound filtering on the N speaker signals and the M microphone signals to obtain a target signal (306). By using this method, better echo filtering effect can be obtained.

A signal processing apparatus is configured to preprocess a sound wave signal and output a processed audio signal through an electromagnetic wave. The signal processing apparatus includes: a receiving unit, configured to receive at least one sound wave signal; a conversion unit, configured to convert the at least one sound wave signal to at least one audio signal; a positioning unit, configured to determine position information related to the at least one sound wave signal; a processing unit, configured to determine a sending time point of at least one audio signal based on the position information and a first time point, where the first time point is a time point at which the receiving unit receives the at least one sound wave signal; and a sending unit, configured to send the at least one audio signal through the electromagnetic wave.