In some embodiments, a method for evaluating headphones during a manufacturing process can include generating a test sound and measuring a response to the test sound from a headphone being evaluated. The method can further include configuring and/or calibrating the headphone based on the measurement. In some embodiments, such a method can be implemented as part of a process for manufacturing of a large number of headphones having active noise cancellation functionality.

The headphones (10) comprise:

a transducer (16) (12);

an noise-canceling processing chain (30, 40) comprising: a microphone (31, 41); a noise-canceling processing filter (34, 44) which comprises in series: a stabilisation filter (34A, 44A) whose transfer function is substantially equal to the inverse of the transfer function of the processed secondary path, and a noise cancellation filter (34B, 44B) whose transfer function is a noise cancellation transfer function.

The secondary path is formed between the transducer (16) and the eardrum, and

the transfer function of the processed secondary path is the transfer function of the secondary path combined with the transfer functions of the processing components, excluding the processing filter (34, 44).

An active noise cancellation (ANC) system is provided with at least one loudspeaker to project anti-noise sound within a passenger cabin of a vehicle in response to receiving an anti-noise signal. At least one microphone provides an error signal indicative of noise and the anti-noise sound within the passenger cabin. An occupancy controller is programmed to modify a transfer function between the at least one microphone and at least one virtual microphone based on an occupancy signal indicative of occupant presence within the passenger cabin. An adaptive filter controller is programmed to filter the error signal using the transfer function to obtain an estimated virtual microphone error signal. A controllable filter generates the anti-noise signal based on the estimated virtual microphone error signal.

In a method for tuning at least one parameter of a noise cancellation enabled audio system with an ear mountable playback device comprising a speaker and a feedforward microphone the playback device is placed onto a measurement fixture, the speaker facing a test microphone located within an ear canal representation. The parameter is varied between a plurality of settings while a test sound is played. A measurement signal from the test microphone is received and stored in the audio system at least while the parameter is varied. A power minimum in the stored measurement signal and a tune parameter associated with the power minimum are determined in the audio system from the plurality of settings of the varied parameter.

In a first system signal processing unit, a first system auxiliary filter generates a correction signal for correcting an error signal from a noise signal, a first system subtractor subtracts the correction signal from an output of a first microphone to obtain an error signal, an adaptive filter performs an adaptive operation using the error signal to generate a cancel sound output from a first speaker, and a DMS detects a position of a user's ear. When the position of the user's ear moves, the controller stops the adaptive operation, updates the transfer function of the first system auxiliary filter to the transfer function corresponding to the noise cancel position matching the position of the user's ear, gradually changes the transfer function of the adaptive filter to the transfer function corresponding to the matching noise cancel position, and resumes the adaptive operation after the change is completed.

A method of reducing signals associated with one or more classes of unwanted noise is disclosed which includes choosing one or more classes as noise to be cancelled while allowing the remainder of classes amongst a plurality of classes to pass through, dividing an incoming time-varying signal into a plurality of snippets having a single or a plurality of durations, transforming each snippet into an associated frequency spectrum, thus generating a plurality of spectra, for each spectrum of the plurality of spectra, identifying presence of the one or more classes chosen as noise, for each identified class of noise, multiplying a 180° phase-shifted version of a frequency signal associated with the identified class of noise by a frequency spectrum of the incoming signal, thereby generating an associated frequency-domain noise-cancelled spectrum, inverse transforming the frequency-domain noise-cancelled spectrum into a time-varying noise-cancelled signal, and outputting the time-varying noise-cancelled signal.

An embodiment electromyography signal detection device includes a noise signal obtaining device configured to obtain a noise signal of an unknown reference frequency at a periphery of a user, an electromyography signal acquisition device configured to measure an electromyography signal from the user, and a controller configured to remove a noise signal included in the electromyography signal of the user based on the obtained noise signal of the unknown reference frequency.

An apparatus for noise reduction in audio signal processing includes a power amplifier, a zero-crossing detector, and a threshold detector. The power amplifier has an input signal terminal for receiving an audio input signal and an output signal terminal. The audio input signal is a digital-to-analog converted version according to a version of a digital audio signal. The power amplifier has an analog gain which is controllable in response to an analog gain control signal. The zero-crossing detector determines a zero-crossing detection signal according to an internal signal provided between the input signal terminal and the output signal terminal. The threshold detector determines a gain setting according to the digital audio signal and the zero-crossing detection signal to generate the analog gain control signal indicating the gain setting, wherein the threshold detector controls the analog gain of the power amplifier according to the analog gain control signal.

In a first system signal processing unit, a first system auxiliary filter generates a correction signal for correcting an error signal from a noise signal, a first system subtractor subtracts the correction signal from an output of a first microphone to obtain an error signal, an adaptive filter performs an adaptive operation using the error signal to generate a cancel sound output from a first speaker, and a DMS detects a position of a user's ear. When the position of the user's ear moves, the controller stops the adaptive operation, updates the transfer function of the first system auxiliary filter to the transfer function corresponding to the noise cancel position matching the position of the user's ear, gradually changes the transfer function of the adaptive filter to the transfer function corresponding to the matching noise cancel position, and resumes the adaptive operation after the change is completed.

A device can include a microphone, a memory configured to store a sound source table including correspondence relationships among boarding items, virtual sound items and filter set values, and a processor configured to receive a sound signal through the microphone and determine a first filter set value matching characteristics of the received sound signal using the sound source table.