The disclosure provides a method and a system for head-related transfer function (HRTF) adaptation. The method includes performing a system identification. The system identification includes a pinna identification and a shadowing identification.

Two subsystems, each including a microphone, a speaker, a canceling sound-generating adder, an error-computing adder, and two adaptive filters and two auxiliary filters that accept two noises as input, are provided in correspondence with two cancellation positions. Each canceling sound-generating adder adds together the outputs from the adaptive filters and outputs the result to the speaker of each subsystem. Each error-computing adder adds together the output from the microphone of the subsystem and the output from the auxiliary filter of the subsystem, and the result is treated as the error of the adaptive filters of each subsystem. A transfer function is learned in advance and set in each auxiliary filter such that each error computed by each error-computing adder becomes zero (0) when a transfer function in which each noise is canceled at each cancellation position in a predetermined standard acoustic environment is set in each adaptive filter.

An example active noise control filtering with an adaptive filter structure includes a controllable filter matrix with reference and error input signals, and updating the filter coefficients dependent on an optional filtered reference signal and an error signal, the error signal being representative of a performance criterion of the filter module. Further, a leakage functionality and a convergence functionality is applied to the updated filter coefficients. The leakage functionality is controlled by at least one of a flush functionality, freeze functionality, spatial freeze functionality and leakage threshold, and the convergence functionality is controlled by the freeze functionality and spatial freeze functionality.

A noise-cancellation system, including: a noise-cancellation filter configured to generate a noise-cancellation signal; an actuator configured to receive the noise-cancellation signal and to transduce a noise-cancellation audio signal based on the noise-cancellation signal, the noise-cancellation audio signal destructively interfering with an undesired noise in a noise-cancellation zone in a predefined volume; an error sensor configured to output an error sensor signal, the error sensor signal being representative of residual undesired noise in the noise-cancellation zone; a performance cost filter configured to receive and filter the error sensor signal and to output a performance cost filter signal, the performance cost filter signal being representative of the error sensor signal as weighted by a performance cost function; and an adjustment module configured to receive the performance cost filter signal and to adjust the noise-cancellation filter such that the noise-cancellation audio signal minimizes the performance cost filter signal.

Two subsystems, each including a microphone, a speaker, a canceling sound-generating adder, an error-computing adder, and two adaptive filters and two auxiliary filters that accept two noises as input, are provided in correspondence with two cancellation positions. Each canceling sound-generating adder adds together the outputs from the adaptive filters and outputs the result to the speaker of each subsystem. Each error-computing adder adds together the output from the microphone of the subsystem and the output from the auxiliary filter of the subsystem, and the result is treated as the error of the adaptive filters of each subsystem. A transfer function is learned in advance and set in each auxiliary filter such that each error computed by each error-computing adder becomes zero (0) when a transfer function in which each noise is canceled at each cancellation position in a predetermined standard acoustic environment is set in each adaptive filter.

A noise-cancellation system, including: a noise-cancellation filter configured to generate a noise-cancellation signal; an actuator configured to receive the noise-cancellation signal and to transduce a noise-cancellation audio signal based on the noise-cancellation signal, the noise-cancellation audio signal destructively interfering with an undesired noise in a noise-cancellation zone in a predefined volume; an error sensor configured to output an error sensor signal, the error sensor signal being representative of residual undesired noise in the noise-cancellation zone; a performance cost filter configured to receive and filter the error sensor signal and to output a performance cost filter signal, the performance cost filter signal being representative of the error sensor signal as weighted by a performance cost function; and an adjustment module configured to receive the performance cost filter signal and to adjust the noise-cancellation filter such that the noise-cancellation audio signal minimizes the performance cost filter signal.

An example active noise control filtering with an adaptive filter structure includes a controllable filter matrix with reference and error input signals, and updating the filter coefficients dependent on an optional filtered reference signal and an error signal, the error signal being representative of a performance criterion of the filter module. Further, a leakage functionality and a convergence functionality is applied to the updated filter coefficients. The leakage functionality is controlled by at least one of a flush functionality, freeze functionality, spatial freeze functionality and leakage threshold, and the convergence functionality is controlled by the freeze functionality and spatial freeze functionality.

An active noise cancellation method and active noise cancellation earphones are provided, which may improve a noise cancellation effect of the active noise cancellation earphones. The method includes: determining a first primary path transfer function according to a first out-of-ear data collected by the out-of-ear microphone and a first in-ear data collected by the in-ear microphone when the speaker plays audio data; determining audio data received by the in-ear microphone according to the first in-ear data, the first out-of-ear data and the first primary path transfer function; determining a first secondary path transfer function according to the audio data played through the speaker and the audio data received by the in-ear microphone; and updating an operation coefficient of the filter to a first operation coefficient according to the first primary path transfer function and/or the first secondary path transfer function.

An audio system for an ear mountable playback device comprises a compensation filter configured to generate a third compensation signal by applying filter operations to an audio signal, and an error compensation unit configured to generate a compensated error signal on the basis of the third compensation signal and a disturbed audio signal from an error microphone. The audio system further comprises a first noise filter configured to be adapted based on the compensated error signal, and a detection unit configured to estimate the acoustic leakage condition on the basis of the first noise filter or of the disturbed audio signal and an audio output signal. The compensation filter is configured to be adapted based on the acoustic leakage condition.

An active noise control device controls a speaker on the basis of an error signal outputted from a detector that has detected, at a control point, a synthesized sound of a noise transmitted from a vibration source and a cancellation sound outputted from the speaker in order to cancel out the noise, and is provided with a control signal generation unit that generates a control signal for controlling the speaker by performing signal processing on a reference signal by a control filter corresponding to an error signal buffered at the end of an input buffer for buffering error signals on a time-series basis.