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.

Noise cancellation systems and methods are provided that receive a reference signal representative of a noise to be reduced and provide a noise cancellation signal based upon the reference signal. Some examples include a feedback signal representative of a residual noise in the environment. At least one of the reference signal, the noise cancellation signal, or the feedback signal is filtered to remove components based upon a rotational rate of a rotating equipment associated with the environment, such as an engine of a vehicle. Accordingly, the noise cancellation system may not interfere with sounds related to the engine.

Audio systems, methods, and computer readable mediums having program code to receive a harmonic signal related to rotating equipment, such as a vehicle drivetrain in some examples, and provide a harmonic cancellation (or enhancement) signal. The harmonic cancellation signal is transduced into an acoustic signal, and a feedback sensor, such as a microphone, detects an error signal representative of acoustic energy at a first location in the environment. A projection filter filters the error signal to provide an estimated error signal at a second location in the environment, such as at the location of an occupant's ear(s). An adaptive module adjusts the cancellation signal based on the estimated error signal.

Embodiments of the present application provide a method and system for active noise control, which can meet different needs of different consumers on sound quality of headphones. The method includes: determining an expected noise control curve of performing active noise control on a target object; determining a target filter according to the expected noise control curve and a filter model; and performing noise control processing on an external noise signal using the target filter.

An active noise control apparatus of vehicles capable of making it difficult for a passenger in a vehicle to hear the voice of another passenger, achieving privacy protection, and a method of controlling the same are disclosed. The active noise control method includes primarily determining a noise level based on a first microphone signal input through a microphone corresponding to a first seat, secondarily determining whether to output an anti-noise signal generated based on the first microphone signal and the magnitude of the anti-noise signal based on the noise level and the level of the first microphone signal, and outputting the anti-noise signal through a headrest speaker of a second seat in response to the secondary determining.

An illustrative controller includes: a transmitter to drive the acoustic transducer to generate acoustic bursts; a receiver to sense a response of the acoustic transducer to echoes; and a processing circuit coupled to the transmitter and to the receiver, the processing circuit configured to convert said received response into output data by: correlating said response to a driving signal to obtain a correlation response; distinguishing peak areas from non-peak areas in said correlation response; deriving a noise level in a portion of said correlation response based on the non-peak areas within said portion; calculating a signal to noise ratio (SNR) for a peak signal within the portion as a ratio of a peak value for the peak signal to the noise level in said portion of said correlation response; and accepting the peak signal as an echo only if the SNR for said peak signal exceeds a predetermined threshold.

A feedback noise reduction method, a feedback noise reduction system, and an earphone are provided. In the method, a channel morphological parameter of an acoustic channel between a microphone and a speaker in a feedback noise reduction system is detected; the feedback noise reduction system is switched from using a first noise reduction filter to using a second noise reduction filter in a case that it is determined that the acoustic channel is in an interfered state based on the channel morphological parameter; and a noise reduction signal is generated by using the second noise reduction filter to cancel a noise signal received by the feedback noise reduction system. A frequency response of the second noise reduction filter in a predetermined frequency band is less than a frequency response of the first noise reduction filter in the predetermined frequency band.

There is provided an ear cup including a housing containing a filter assembly and a motor-driven impeller for creating an airflow through the filter assembly, the housing including an air outlet downstream from the filter assembly for emitting the filtered airflow from the housing. The ear cup further includes an acoustic driver carried by the housing, a reference internal noise sensor carried by the housing, and active noise control circuitry that is configured to use a signal provided by the reference internal noise sensor to operate the acoustic driver.

There is provided an ear cup including a housing containing a filter assembly and a motor-driven impeller for creating an airflow through the filter assembly, the housing including an air outlet downstream from the filter assembly for emitting the filtered airflow from the housing. The ear cup further includes an acoustic driver mounted to the housing, a reference internal noise disposed within the housing and a reference ambient noise mounted to the housing. The ear cup further includes active noise control circuitry that is configured to simultaneously use both a signal provided by the reference internal noise and the signal provided by the reference ambient noise to operate the acoustic driver.

A noise reduction device includes a processor that converts a noise signal collected by a microphone disposed in a control space into a noise signal in a frequency domain, a storage that stores the converted noise signal in the frequency domain as a reference signal, and a signal generator that generates a noise reduction signal for reducing the noise signal collected by the microphone at a control position of the control space. The processor determines whether or not the noise signal is non-stationary noise based on a frequency characteristic of the converted noise signal in the frequency domain and a frequency characteristic of the reference signal. When it is determined that the noise signal is the non-stationary noise, the processor controls the signal generator so as to cancel generation of the noise reduction signal.