An adaptive noise canceling (ANC) circuit adaptively generates an anti-noise signal from a reference microphone signal that is injected into the speaker or other transducer output to cause cancellation of ambient audio sounds. An error microphone proximate the speaker provides an error signal. A secondary path estimating adaptive filter estimates the electro-acoustical path from the noise canceling circuit through the transducer so that source audio can be removed from the error signal. Tones in the source audio, such as remote ringtones, present in downlink audio during initiation of a telephone call, are detected by a tone detector using accumulated tone persistence and non-silence hangover counting, and adaptation of the secondary path estimating adaptive filter is halted to prevent adapting to the tones. Adaptation of the adaptive filters is then sequenced so any disruption of the secondary path adaptive filter response is removed before allowing the anti-noise generating filter to adapt.

A quiet headspace for the passenger in a vehicle (car/train/bus/aircraft etc.) which comprises a canopy to provide some passive attenuation of the noise coming from the surroundings and within the canopy a noise reduction system comprising, in combination one or more loudspeakers and one or more microphones located close to the passenger's head, and one or more microphones located around the periphery of the canopy.

A personal audio device, such as a wireless telephone, includes an adaptive noise canceling (ANC) circuit that adaptively generates an anti-noise signal from a reference microphone signal and injects the anti-noise signal into the speaker or other transducer output to cause cancellation of ambient audio sounds. An error microphone is also provided proximate to the speaker to provide an error signal indicative of the effectiveness of the noise cancellation. A secondary path estimating adaptive filter is used to estimate the electro-acoustical path from the noise canceling circuit through the transducer so that source audio can be removed from the error signal. A level of the source audio with respect to the ambient audio is determined to determine whether the system may generate erroneous anti-noise and/or become unstable.

A first control signal filter to which a cosine wave oscillating at a control frequency is input; a second control signal filter to which a sine wave oscillating at the control frequency is input; a control signal adder for outputting a control signal generated by adding an output of the first control signal filter and an output of the second control signal filter; a filter coefficient update unit for updating filter coefficients of the first control signal filter and the second control signal filter; and a frequency correction value calculation unit for calculating a frequency correction value for correcting the control frequency on the basis of the control signal and the control frequency.

An apparatus for realizing an active noise cancellation control law transfer function between a sensing microphone and a speaker. The apparatus includes a multiplicity of filters. Each filter is operable over a different frequency range. At least one filter has an adjustable parameter whereby the filter can be adjusted such that the filters cumulatively realize a required control law transfer function. The adjustable parameter may in one embodiment be the amplitude. In other embodiments, it may be other parameters.

Sound reduction includes receiving a reference signal corresponding to undesired sound present in the target space, and producing, based on the reference signal, a cancelling signal representative of the undesired sound present in the target space. Sound reduction further includes producing, based on the cancelling signal, sound to destructively interfere with the undesired sound present in the target space, and delaying at least one of the reference signal and the cancelling signal to reduce or compensate for runtime differences between signal paths that transfer the reference signal to the target space.

In accordance with embodiments of the present disclosure, a processing circuit may implement an adaptive filter, a first signal injection portion which injects a first additional signal into a first frequency range content source audio signal, and a second signal injection portion which injects a second additional signal into a second frequency range content source audio signal, wherein the first additional signal and the second additional signal are substantially different. The adaptive filter may have a response that generates the antinoise signal from the reference microphone signal to reduce the presence of the ambient audio sounds at the acoustic output, wherein the response of the adaptive filter is shaped in conformity with the reference microphone signal and the error microphone signal by adapting the response of the adaptive filter to minimize the ambient audio sounds in the error microphone signal, wherein the antinoise signal is combined with at least the first frequency range content source audio signal.

Differing from conventionally-used exhaust pipe utilizing discontinuous section area(s) and sound-absorbing material(s) to abate the noise produced by an engine, the present invention provides a waste air exhausting device consisting of: a housing, a supporting plate disposed in the housing, a miniature microphone disposed at the end of the housing, and a loudspeaker disposed on the supporting plate. Therefore, according to the noise produced by the engine, a noise controller system coupling to the miniature microphone and the loudspeaker is able to produce an anti-noise signal through the loudspeaker for abating the engine noise. On the other hand, the noise controller system can also produce an anti-noise signal having specific frequencies components according to the frequency of the engine noise and a reference signal, so as to modulate the frequency of the engine noise by broadcasting the anti-noise signal having the specific frequencies components in the housing through the loudspeaker.

A kit for attenuation of noise includes a noise source audio transducer, two ear pieces, and a control unit. The two ear pieces have respective resilient bodies that engage outer portions of ear canals of respective ears of a user while respective in-ear transducers of the two ear pieces are respectively positioned in inner portions of the ear canals. The respective in-ear transducers detect discrepancies (e.g., incomplete superpositioning) between the noise and the anti-noise. The respective in-ear transducers optionally detect respective secondary path effects in the ear canals. The noise source audio transducer detects noise generated by a noise source (e.g., snoring noise). The control unit configures an adaptive filter based at least in part on an error signal, and optionally based in part on secondary path effects. The control unit generates signals representative of anti-noise. The two ear pieces produce the anti-noise responsive to the signals. The two ear pieces produce masking noise with sound level that varies in direct correlation with sound level of the noise generated by the noise source.

A method performed by an audio system that includes a headset with a left headset housing and a right headset housing. The method includes driving a speaker of the left headset housing with an audio signal, determining whether audio howl is present within the left headset housing by comparing spectral content from a first error microphone signal produced by a first error microphone of the left headset housing and spectral content from a second error microphone signal produced by a second error microphone of the right headset housing, and, in response to determining that audio howl is present, filtering the audio signal to mitigate the audio howl.