A method for noise cancellation includes monitoring a system for a current operating point, monitoring the system for a predetermined disturbance, and in response to the predetermined disturbance, determining the disturbance to be in one of a transient or steady state response period. A set of data is selected corresponding to the current operating point of the system, the disturbance, and the response period from a database containing predetermined noise cancellation waveform data. A noise cancelling waveform is output to audio transducers based upon the selected set of data.

An active noise reduction device includes: a reference signal input terminal that receives a reference signal from a reference signal source attached to an automobile; a simulated vibration transfer characteristics filter unit that generates a second signal by correcting, using simulated vibration transfer characteristics, a first signal for outputting, from a loudspeaker attached to the automobile, a sound different from a canceling sound, the simulated vibration transfer characteristics simulating vibration transfer characteristics from the loudspeaker to the reference signal source; a first subtracter that outputs a corrected reference signal obtained by subtracting the second signal generated, from the reference signal received by the reference signal input terminal; and an adaptive filter unit that applies an adaptive filter to the corrected reference signal outputted from the first subtracter to generate a canceling signal to be used to output the canceling sound.

A notebook computer includes a control chip, a speaker, and the fan. The control chip and the fan are disposed inside a chassis of the notebook computer. The method includes: controlling, by the control chip, the speaker to send a first sound signal, where the first sound signal and a first noise signal that is generated by running of the fan have opposite phases and a same frequency. The first sound signal is used to cancel the first noise signal.

An active noise reduction system reduces a noise in an internal space of a mobile body. The active noise reduction system includes a controller configured to control a canceling sound output device. The controller is configured to generate a first canceling estimation signal as an estimation signal of a canceling sound at a position of an error detector based on a reference signal, generate a second canceling estimation signal as an estimation signal of the canceling sound at a head position of an occupant by adjusting a time delay and an amplitude of the first canceling estimation signal based on a reference distance, and update a control filter for controlling the canceling sound output device based on the second canceling estimation signal.

An active noise reduction system includes a reference signal generator configured to generate a reference signal, a canceling sound generator configured to generate a canceling sound, an error detector configured to detect an error between a noise and the canceling sound and generate an error signal corresponding to the error, and a controller configured to control the canceling sound generator based on the reference signal and the error signal, wherein the controller is configured to update an estimation value of acoustic characteristics in an internal space of a mobile body based on the reference signal and the error signal, estimate a head position of an occupant in the internal space based on the updated estimation value of the acoustic characteristics, and update a control filter based on the estimated head position of the occupant, the control filter being a filter for controlling the canceling sound generator.

A noise cancelling system for a vehicle includes a microphone, at least one first sensor configured to collect first data related to an element that generates a noise sound, at least one second sensor configured to collect second data related to an element that changes a secondary path of the noise sound, a controller configured to select a secondary path model corresponding to the second data from among a plurality of pre-stored secondary path models, input the first data to a secondary path filter corresponding to the selected secondary path model, and generate an anti-noise signal based on output data of the secondary path filter and error data received from the microphone, and a speaker configured to output an anti-noise sound based on the anti-noise signal.

A work machine includes a housing. The housing at least partly houses a machine. The housing has an opening. The work machine includes a path leading into the housing from the opening. The work machine includes a controller and a speaker. The controller is configured to cause a speaker to output a control sound for reducing operating noise. The operating noise is generated in the housing by motion of the machine and propagates in the path from a source of the operating noise to the opening. The speaker is arranged so that the control sound propagates in the path with its wavefront parallel to a wavefront of the operating noise that propagates in the path.

An assembly actively controls the rolling noise for a motor vehicle. The assembly includes a path control device that includes another sensor fastened on the steering knuckle, such as an accelerometer. The path control device is capable of transmitting, to the anti-noise device, measurements obtained by the other sensor. The anti-noise device is capable of generating an anti-noise signal depending on the acceleration measurements obtained and controlling its transmission via the loudspeaker.

A noise control system detects, identifies, and cancels specific, preselected sounds that an operator does not want to hear during operation of a machine. One or more of a microphone or another sensor detects sound vibrations or other operational parameters that result in the generation of sound vibrations during operation of the machine. A controller identifies, and selectively cancels only the specific, preselected sounds the operator does not want to hear while operating the machine by generating an anti-noise signal to interfere with the specific, preselected sounds.

A transfer function measuring method includes: outputting a first signal to each of a plurality of loudspeakers to cause the plurality of loudspeakers to simultaneously output sounds with mutually different frequencies; acquiring second signals output from a microphone as a result of acquiring the sounds with the mutually different frequencies; and calculating a transfer function of each of the sounds with the mutually different frequencies based on the first signal and the second signals.