A face mask can both actively cancel sounds and passively attenuate sounds spoken by the user to prevent the sounds from reaching non-intended recipients positioned near the user. The mask can not only reduce the user's voice from escaping the mask but can also be used to reduce external sounds from reaching inside the mask. Thus, a user can wear the mask in public and talk on their phone without disturbing others around them. The mask can include at least one microphone and at least one audio speaker disposed inside and/or outside the mask. Sounds received by the microphone can be processed by a microphone and computing electronics to provide an output to the audio speaker that can appropriately attenuate the sound received by the microphone, via acoustic cancelation. The mask can not only be used to cancel sounds but may also be used to amplify sounds when desired.

An active noise control device includes a control signal generating unit including a first adaptive filter configured to generate a control signal by performing a filtering process on a reference signal corresponding to noise, an identifying unit configured to identify a peak frequency in an impedance frequency characteristic of an actuator, a peak frequency storage unit configured to store an initial peak frequency of the actuator, a first determination unit configured to determine whether or not a difference between the peak frequency currently identified and the initial peak frequency is greater than or equal to a threshold value, and a control unit configured to change a characteristic of the control signal generated by the control signal generating unit when the first determination unit determines that the difference is greater than or equal to the threshold value.

A howling detector is described that is configured to receive an input signal and to determine measure of the linearity of a logarithmic representation of the energy of the input signal. In some examples, this triggers gain adjustment (e.g. of a noise control unit) and, in some further examples, the amount of the gain adjustment may be based on an estimation of the maximum stable gain of a noise control unit.

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.

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.

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.

In one aspect a method that includes receiving an input signal captured by one or more first sensors associated with an active noise reduction (ANR) device, and processing the input signal using a first filter disposed in an ANR signal path to generate a first signal for an acoustic transducer of the ANR device. The input signal is processed in a pass-through signal path disposed in parallel with the ANR signal path to generate a second signal for the acoustic transducer, wherein the pass-through signal path allows a portion of the input signal to pass through to the acoustic transducer in accordance with a variable gain. One or more second sensors detect an existence of a condition likely to cause instability in the pass-through signal path, and in response, the variable gain is adjusted. A driver signal for the acoustic transducer is generated using an output based on the adjusted gain.

Active noise cancellation systems and methods include a feedforward path configured to receive a reference signal comprising ambient noise and adaptively generate an anti-noise signal to cancel the ambient noise. The adaptive filter is tuned in accordance with at least one parameter, which is set by a logic device configured to determine an ambient noise condition based the reference signal by estimating a fullband power of the reference signal, estimating a low-frequency power of the reference signal, comparing the fullband power and low-frequency power to one or more thresholds, and/or setting one or more ambient noise flags. The ambient noise condition may include a quiet background, a wideband noise condition, and/or a low-frequency dominant noise condition.

The technology described in this document can be embodied in a computer-implemented method that includes receiving a portion of a feedback signal of an active noise control (ANC) system, and processing the portion of the feedback signal using an adaptive line enhancer (ALE) filter to detect a tonal signature. The method also includes determining, by one or more processing devices, that the tonal signature represents an unstable condition, and responsive to determining that the tonal signature represents an unstable condition, generating one or more control signals for adjusting one or more parameters of the ANC system, to mitigate the unstable condition.

An active noise control system selects one reference sensor providing a reference signal with the largest coherence to a noise signal, among a plurality of available reference sensors, as a first entry of a reference sensor set. After selecting the first entry, the active noise control system repeats a process in which a sensor capable of providing the largest information quantity to a current reference sensor set among remaining sensors is selected as a new entry of a reference sensor set, until a desired number of sensors is reached or a desired control level is reached. When the reference sensor set is determined, the active noise control system utilizes the entries of the reference sensor set to generates a noise control signal suitable for canceling the noise signal.