A road noise cancellation (RNC) system may include a signal analysis controller for detecting non-stationary, transient events based on sensor signals having a spectral or temporal character significantly different from steady-state road or cabin noise. Upon detection of such non-stationary events, the RNC system may modify the sensor signals to mask the non-stationary event, thereby preventing the RNC system's adaptive filters from mis-adapting because of transient, non-stationary events. Alternatively, the RNC system may pause or slow or pause adaptation of its controllable filters for the duration of a frame that includes the non-stationary event.

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 audio processing system is provided with a speaker, a plurality of microphones, and an audio processing device. The audio processing device includes a plurality of filters that allow audio signals of audio collected by the plurality of microphones to pass any respective first bands included in a band of the audio output from the speaker, a plurality of delayers that delay the audio signals passed through the plurality of filters by delay times corresponding to the first bands respectively, a correlation value calculator that calculates a correlation value of a plurality of audio signals delayed respectively by the plurality of delayers and an audio signal of the audio output from the speaker, and a determinator that determines presence or absence of abnormality in the plurality of microphones and the speaker based on the correlation value.

In a signal processing device, a signal processing method, a recording medium, and a rangehood apparatus, a filter coefficient is set in a sound cancelling filter, and the sound cancelling filter outputs a cancellation signal. A coefficient calculator calculates a first filter coefficient. An oscillation suppressor calculates a second filter coefficient by applying a window function to the first filter coefficient to set the second filter coefficient as the filter coefficient.

A system for detecting divergence in a noise-cancellation system, comprising: a controller configured to: determine a power of a component of the error signal, the component being correlated to the at least one reference sensor signal; determine an average value, over a first time period, of a value representative of a time gradient of the power of the component of the error signal; and determine whether the average value is greater than a threshold.

A road noise cancellation (RNC) system may include a signal analysis controller for detecting non-stationary, transient events based on sensor signals having a spectral or temporal character significantly different from steady-state road or cabin noise. Upon detection of such non-stationary events, the RNC system may modify the sensor signals to mask the non-stationary event, thereby preventing the RNC system's adaptive filters from mis-adapting because of transient, non-stationary events. Alternatively, the RNC system may pause or slow or pause adaptation of its controllable filters for the duration of a frame that includes the non-stationary event.

[Object] To shorten a time until an effect is obtained after start of an adaptive process mode on an ambient sound.

[Solution] Provided is a signal processing device including: a noise cancellation processing unit configured to generate a noise cancellation signal on the basis of a collected ambient sound; a signal processing unit configured to generate an ambient sound adapted signal by performing dynamic analysis related to a feature of the ambient sound and filtering the ambient sound; and a control unit configured to control a plurality of modes related to signal processing. The plurality of modes includes a first mode in which acoustic reproduction based on the noise cancellation signal is performed and a second mode in which acoustic reproduction based on the noise cancellation signal and the ambient sound adapted signal is performed, and the signal processing unit continues the dynamic analysis even in the first mode.

An apparatus includes a noise reduction headphone comprising one or more microphones and an acoustic transducer, the one or more microphones configured to generate an input signal; and a controller comprising one or more processing devices, the controller configured to: process the input signal through one or more noise reduction filters to generate a noise-reduction signal, compare the input signal to an estimate of ambient noise to determine if the energy of the input signal is greater than the estimate of ambient noise, wherein if the energy of the input signal is greater than the estimate of ambient noise by a predetermined amount, a change in the noise reduction signal is suppressed; and generate an output signal, the output signal comprising, at least in part, the noise-reduction signal, wherein the acoustic transducer is configured to produce an acoustic output in accordance with the output signal.

A playback audio signal is combined with a feedback signal from a feedback microphone to provide a first combined signal. The first combined signal is filtered with a feedback filter to provide a driver command signal. The driver command signal is provided to an acoustic transducer for transduction to acoustic energy. The first combined signal is compared with the feedback signal to detect a feedback instability based upon the comparison.

The application describes techniques for howling detection. A processing module for a noise control circuit is described. The processing module comprises a howling detector configured to receive an input signal and to determine a log-linearity metric based on the input signal. Gain adjustment of the noise control unit following the detection of howling is also described, wherein the amount of gain adjustment may be based on an estimation of the maximum stable gain of the noise control unit.