Noise abatement within a signal stream containing unwanted signal referred to as noise is performed by acquiring a digitized noise signal and using a digital processor circuit to subdivide the acquired noise signal into different frequency band segments and thereby generate a plurality of segmented noise signals. Then individually for each segmented noise signal, the processor shifts in time the segmented noise signal by an amount dependent on a selected frequency of the segmented noise signal to produce a plurality of shifted segmented noise signals. The precise time shift applied to each noise segment considers the frequency content of the segment and the system processing time. Individually for each segmented noise signal, amplitude scaling is applied. The shifted and amplitude-scaled segmented noise signals are then combined to form a composite anti-noise signal which is output into the signal stream to abate the noise through destructive interference.

The present invention provides an audio adjustment method and associated audio adjustment device for active noise cancellation. The audio adjustment method includes: broadcasting a single tone having a frequency f.sub.k; generating M sets of filtering coefficients regarding the frequency f.sub.k, wherein each set of filtering coefficients within the M sets of filtering coefficients includes a combination of an amplitude and a phase, and the M sets of filtering coefficients are different from one another; determining an m.sup.th set of filtering coefficients from the M sets of filtering coefficients to minimize energy corresponding to the frequency f.sub.k; and adjusting the single tone with the m.sup.th set of filtering coefficients to obtain an adjusted single tone corresponding to the frequency f.sub.k.

An active noise cancellation (ANC) system including a selectable decimation rate decimator that receives an oversampled digital input and has an input that selects the decimation rate, a filter that receives an output of the decimator, and a selectable interpolation rate interpolator that receives an output of the filter and has an input that selects the interpolation rate. The selectable decimation rate decimator and the selectable interpolation rate interpolator operate to provide a selectable sample rate for the filter based on the selected decimation and interpolation rates. The filter may be an anti-noise filter, feedback filter, and/or a filter that models an acoustic transfer function of the ANC system. Rate selection may be static, or dynamically controlled based on battery or ambient noise level. A ratio of the decimation rate and the interpolation rate is fixed independent of the dynamically controlled decimation and interpolation rates.

An audio processing device (100) includes a correction microphone (110), a reference microphone (120), a classification unit (130), an active noise cancellation (ANC) unit (140), and a speaker (150). The correction microphone is arranged in an area adjacent to an ear of a user of the device and picks up acoustic signals in the area and outputs same as a correction signal. The reference microphone picks up surrounding noises (124) from a surrounding area of the user and outputs same as a reference signal. The classification unit receives the reference signal and splits the reference signal corresponding to a spectrum and amplitude thereof into signal components of two or more classes and outputs a classified signal. The ANC unit receives and processes the correction signal based on the classified signal and outputs a corresponding audio signal. The speaker receives the audio signal and provides a corresponding acoustic signal output.

According to one embodiment, a system for reducing interference noise of rotor and stator blades includes rotor blades, stator blades, loudspeakers, one or more reference microphones, and a controller. The rotor blades rotate about a central axis. The loudspeakers are discretely arranged on a circle that has a center positioned on the central axis. Each loudspeaker generates a control sound. The controller causes the loudspeakers to generate control sounds of a same phase and a same amplitude. The control sounds correspond to the loudspeakers. The r is selected based on a preset attenuation level concerning the interference noise, and the k, where a is a length of the rotor blades, b is a radius of the circle, r =a/b, k is an upper limit wavenumber.

An active vibration noise control system is applied to a vehicle provided with an EPS motor to change behavior of the vehicle. The active vibration noise control system includes an ANC processor configured to receive acoustic information at a predetermined position in a vehicle compartment as an error signal and control a vibration noise based on a reference signal correlate with the vibration noise and the error signal that is received and an inverse electromotive force information receiving section receiving information on an inverse electromotive force induced on the EPS motor by behavior change of the vehicle. The ANC processor utilizes as a reference signal the information on the inverse electromotive force received by the inverse electromotive force information receiving section. The active vibration noise control system actively controls the vibration noise generated in the vehicle.

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.

Various technologies described herein pertain to active noise cancellation in the interior of a vehicle. In exemplary embodiments, a microphone mounted on the vehicle outputs an audio signal indicative of noise emitted by a noise source. A computing system of the vehicle determines a position of the noise source based upon sensor signals output by sensors mounted on the vehicle. The computing system further determines a position of a passenger in the vehicle based upon a sensor mounted inside the vehicle. The computing system generates a complementary signal that is configured to attenuate the noise based upon the audio signal, the position of the noise source, and the position of the passenger. The complementary signal is then output by way of a speaker in the interior of the vehicle.

Embodiments are disclosed relating to an active noise reducing system and method for a headphone with a rigid cup-like shell which has an outer surface and an inner surface that encompasses a cavity with an opening. The system and method include picking up sound at least at three positions that are regularly distributed over the outer surface, and providing a first electrical signal that represents the picked-up sound. The system and method further include: filtering the first electrical signal to provide a second electrical signal, and generating in the opening of the cavity sound from the second electrical signal. Filtering is performed with a transfer characteristic that is configured so that noise that travels through the shell from beyond the outer surface to beyond the inner surface is reduced by the sound generated in the opening.

An in-ear device includes a housing shaped to hold the in-ear device in an ear, and an audio package, disposed in the housing, to emit sound. A tympanic membrane measurement unit (TMMU) is structured to measure a movement of a tympanic membrane in the ear caused by external sound received by the tympanic membrane, and a controller is coupled to the audio package and the TMMU. The controller includes logic that when executed by the controller causes the in-ear device to perform operations. The operations include measuring a movement of the tympanic membrane, and in response to measuring the movement of the tympanic membrane, outputting sound from the audio package to destructively interfere with the external sound received by the tympanic membrane.