A noise reducing device includes: an acoustic-to-electric conversion section for collecting noise and outputting an analog noise signal; an analog-to-digital conversion section for converting the analog noise signal into a digital noise signal; and a digital processing section for generating a digital noise reducing signal on a basis of the digital noise signal and a desired parameter. The device further includes: a retaining section for retaining a plurality of parameters corresponding to a plurality of kinds of noise characteristics; a setting section for setting one of the plurality of parameters as the desired parameter of the digital processing section; a digital-to-analog conversion section for converting the digital noise reducing signal into an analog noise reducing signal; and an electric-to-acoustic conversion section for outputting noise reducing sound on a basis of the analog noise reducing signal.

An electrostatic transducer including a membrane, a first electrode and a second electrode. The first electrode is disposed parallel to the membrane. The membrane is configured to respond mechanically to a varying first electric field in accordance with respective electric potentials applied between the first electrode and the membrane. The second electrode is disposed parallel to the membrane opposite from the first electrode. The membrane is configured to respond mechanically to a varying second electric field in accordance with respective electric potentials between the second electrode and the membrane. The first and second electrodes have through holes configured for acoustic transmission to and from the membrane. The housing includes: (i) a nozzle configured for acoustic transmission from the membrane through the holes of the first electrode to an ear canal and (ii) an aperture configured to provide acoustic transmission through the holes of the second electrode between the membrane and air external to the housing.

An active noise control device controls a speaker so as to output a canceling sound for canceling noise transmitted from a vibration source. The active noise control device includes a control signal generating unit configured to perform signal processing on a basic signal corresponding to a predetermined frequency by a feedback filter and a extraction filter, which is an adaptive notch filter, to generate a control signal that control the speaker, a secondary path filter updating unit configured to update sequentially and adaptively a secondary path filter, and a feedback filter setting unit configured to set the feedback filter based on the secondary path filter.

An active noise reduction system using adaptive filters. A method of operation the active noise reduction system includes smoothing a stream of leakage factors. The frequency of a noise reduction signal may be related to the engine speed of an engine associated with the system within which the active noise reduction system is operated. The engine speed signal may be a high latency signal and may be obtained by the active noise reduction system over audio entertainment circuitry.

A treadmill having a running deck comprising a motor arranged to drive movement of a tread belt, a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions are executable by the processor to determine an anti-phase waveform based on waveform attributes of a noise emitted from the treadmill and to cause a sound of the anti-phase waveform to be emitted into a surrounding environment.

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.

An electric powered work machine according to one aspect of the present disclosure includes a first and a second digital filters, a control sound source, an error sensor, and a characteristics adjustor. The first digital filter includes a series of taps and generates a control signal. The control sound source produces an artificial noise in accordance with the control signal. The error sensor converts a synthesized sound of the artificial noise and a target noise at a canceling location to an error signal. The second digital filter includes N taps and generates a filtered reference signal. The characteristics adjustor uses the error signal and the filtered reference signal to adjust a coefficient of each tap of M taps in the series of taps. Each of M and N is a positive integer satisfying M<N.

An active noise control device includes a secondary path filter coefficient updating unit. The secondary path filter coefficient updating unit is configured to update a coefficient of a secondary path filter by using a coefficient of the secondary path filter after previous updating as a previous value, when a phase characteristic of the secondary path filter that sets an initial value as the coefficient and a phase characteristic of the secondary path filter that uses the previous value as the coefficient are not approximate to each other.

An active noise control device includes a control signal generating unit including a first adaptive filter configured to generate a control signal by performing a filtering process on a reference signal corresponding to noise, an identifying unit configured to identify a peak frequency in an impedance frequency characteristic of an actuator, a peak frequency storage unit configured to store an initial peak frequency of the actuator, a first determination unit configured to determine whether or not a difference between the peak frequency currently identified and the initial peak frequency is greater than or equal to a threshold value, and a control unit configured to change a characteristic of the control signal generated by the control signal generating unit when the first determination unit determines that the difference is greater than or equal to the threshold value.

An active noise control device includes a first adaptive filter configured to generate a control signal by performing a filtering process on a reference signal corresponding to noise, and a first filter coefficient updating unit configured to update a filter coefficient of the first adaptive filter based on based on the reference signal and an added error signal acquired by adding a first error signal acquired by detecting residual noise by a first microphone and a second error signal acquired by detecting residual noise by a second microphone.