A method for reducing noise in at least one monitor position in a vehicle compartment by actively controlling the power of a primary noise (d.sub.m(t)) as sensed at two or more control positions in the vehicle compartment, the method comprising the updating of filter coefficient(s) of (an) adaptive filter(s) (w(n)) based on variable contribution of error sensors and actuator(s) for different noise source operating conditions.

Active noise control systems and methods are disclosed that include generating with a first sub-system, anti-noise that is configured to reduce or cancel noise occurring at a listening position. Generating with a second sub-system, anti-noise that is configured to reduce or cancel noise occurring at the listening position. The first active noise control sub-system has a higher robustness than the second active noise control sub-system.

A 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 various temporal or frequency domain amplitude characteristics. 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. This may include adjusting a leakage value of an adaptive filter controller.

A conversation support device includes: a speaker; a microphone; a noise source acquisition unit that acquires a noise signal indicating noise; a first calculator that calculates a transfer characteristic of a secondary path between the speaker and the microphone; an echo cancellation unit that cancels an echo by using the transfer characteristic of the secondary path; a second calculator that calculates a coefficient of an adaptive filter, based on the transfer characteristic of the secondary path and the noise signal; and an active noise cancellation controller that generates a noise cancelling signal by using the coefficient of the adaptive filter and the noise signal. The noise cancelling signal is for controlling cancellation of the noise.

A propagation delay identification system for active noise cancelation for a vehicle audio system may include at least one sensor configured to transmit sensor data indicative of acceleration data, hammer data and microphone data, at least one output sensor configured to transmit an impulse response, and a processor. The processor may be programmed to receive the sensor data and pulse function, identify a propagation path delay between the microphone data and a cross-correlation between the acceleration data and hammer data, and generate a source pulse function. The processor further identify a secondary path delay based on an arrival time of peak energy of a convolution of the impulse response and filtered pulse function, and apply a binary limiter to a reference signal in response to the secondary path delay exceeding the propagation path delay to reduce boosting of an audio signal based on coherent reference and error signals.

A method of operating a personal audio device configured to be removed from and inserted into a user's ear can include generating an input signal by an input signal generating device. The method can also include determining whether an insertion event has occurred based on the generated input signal and causing the personal audio device to operate in a low power mode responsive to an absence of an insertion event determination after a first period of time. The method can also include causing the personal audio device to operate in an ultra-low power mode responsive to the absence of an insertion event determination after a second period of time that occurs after the first period of time, the ultra-low power mode having a lower power consumption than the low power mode.

A first cancellation signal output from a first speaker cancels noise at a first cancellation point, which is a typical position of the right ear of a user, together with a second cancellation signal output from a second speaker. In addition, the second cancellation signal output from the second speaker cancels noise at a second cancellation point, which is a typical position of the left ear of the user, together with the first cancellation signal output from the first speaker. The first speaker and the second speaker are arranged side by side on a second line segment, which passes through the midpoint of a first line segment connecting the first cancellation point and the second cancellation point to each other and is perpendicular to the first line segment, and a range where the relationship between noise and the first cancellation signal and the second cancellation signal is the same as that at the cancellation point is extended.

Adaptive filters output a cancellation sound from a speaker, a selector selects outputs of a plurality of auxiliary filters each corresponding to different positions, a subtractor subtracts the selected output from the output of the microphone and outputs the subtracted output to the adaptive filter as an error signal, and a position detection device detects a position of a head of a user. A transfer function estimated so that the error signal becomes 0 when noise is canceled at the corresponding position is preset in the auxiliary filter. When the auxiliary filter corresponding to the position close to the head of the user changes, the switching control unit stepwise increases the frequency with which the output of the auxiliary filter is selected by the selector to 100%.

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 (.sub.m(n)) between an electrical error signal (e.sub.m(n) and a modelled secondary anti-noise signal .sub.m(n) with at least one predefined threshold (, ).

A sound signal control device in a device including an input transducer to detect sound in a space in a vehicle, a sensor to image an occupant in the space, and an output transducer to emit sound into the space includes: a controller to generate information indicating a position of a head of the occupant and information indicating a state of the occupant, based on an image imaged by the sensor; a processor to generate a cancellation signal for cancelling noise at the position based on a sound signal representing sound detected by the input transducer and the information, and generate a control signal for controlling sound at the position based on the cancellation signal; and a converter to cause the output transducer to emit a sound corresponding to the control signal. The processor adjusts a degree to which the noise is cancelled, based on the information indicating the state.