An input signal representative of an undesired acoustic noise in a region is captured by one or more first sensors and processed to generate a cancellation signal. An output signal is generated based on the cancelation signal to cause one or more acoustic transducers to cancel, at least in part, the undesired acoustic noise in the region. A feedback signal representative of residual acoustic noise in the region is captured by one or more second sensors. A characteristic of each of the feedback signal, the cancellation signal, and a combination of the cancellation signal and the feedback signal is determined. One or more thresholds are compared to a ratio of (i) the characteristic of the combination of the cancellation signal and the feedback signal and (ii) a combination of the characteristic of the feedback signal and the characteristic of the cancellation signal to determine a convergence state.

An active noise reduction device includes a first adaptive filter, a first filter coefficient updater, and a controller that determines, based on a first parameter of the first adaptive filter, whether first noise control based on a first cancelling sound is in a stable state or an unstable state. The controller transitions the first filter coefficient updater to a restriction state in which an effect of reducing first noise is smaller than in a normal state when it is determined that the first noise control is in the unstable state while the first filter coefficient updater is updating a coefficient of the first adaptive filter in the normal state, and transitions the first filter coefficient updater back to the normal state when it is determined that the first noise control is in the stable state while the first filter coefficient updater is in the restriction state.

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.

An audio system for an ear mountable playback device includes a speaker, an error microphone, which senses sound being output from the speaker, and a sound control processor. The processor is configured for controlling and/or monitoring a playback of a detection signal or a filtered version of the detection signal via the speaker, recording an error signal from the error microphone, and determining whether the playback device is in a first state, where the playback device is worn by a user, or in a second state, where the playback device is not worn by a user, based on processing of the error signal.

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 active noise reduction device includes a first adaptive filter, a first filter coefficient updater, and a controller that determines, based on a first parameter of the first adaptive filter, whether first noise control based on a first cancelling sound is in a stable state or an unstable state. The controller transitions the first filter coefficient updater to a restriction state in which an effect of reducing first noise is smaller than in a normal state when it is determined that the first noise control is in the unstable state while the first filter coefficient updater is updating a coefficient of the first adaptive filter in the normal state, and transitions the first filter coefficient updater back to the normal state when it is determined that the first noise control is in the stable state while the first filter coefficient updater is in the restriction state.

A headset system comprises: a headset comprising at least one microphone and at least one speaker and configured to transmit and receive sound; a wire system coupled to the headset and comprising a wire; and a control unit coupled to the wire system and configured to: receive from the wire a combined signal comprising a first signal and a second signal, determine that the first signal is a spurious signal, and detect a failure of the wire system based on the determining.

A method for reducing the power of an acoustic primary noise signal (d.sub.m(n)) at one or more control positions in a vehicle passenger compartment using an adaptive filter. The method comprising to compare a mean correlation coefficient (γ.sub.m(n)) between an electrical error signal (e.sub.m(n) and a modelled secondary anti-noise signal ŷ.sub.m(n) with at least one predefined threshold (α, β).

An active vibratory noise reduction system includes: a canceling vibratory sound generator; an error signal detector for detecting a canceling error between the canceling vibratory sound and a vibratory noise as an error signal; and an active vibratory noise controller for generating, based on the error signal, a control signal for controlling the canceling vibratory sound generator. The active vibratory noise controller is provided with a stability improving unit including: a correction value generation unit for generating an error signal correction value by multiplying a reaching control sound estimation value by a stabilization coefficient; an error signal correction unit for correcting the error signal by using the error signal correction value to generate a corrected error signal, and a stabilization coefficient updating unit for sequentially updating the stabilization coefficient based on the corrected error signal and the reaching control sound estimation value by using an adaptive algorithm.