Abstract: In the frequency domain, the method comprises the following steps: a) calculating a first noise reference by analyzing the spatial coherence of the signals picked up; b) calculating a second noise reference by analyzing the directions of incidence of the signals picked up; c) estimating a main direction of incidence of the signals picked up; d) selecting as a referent noise signal one or the other of the noise references as a function of the estimated main direction; e) combining the signals picked up into a noisy combined signal; f) calculating a probability that speech is absent in the noisy combined signal on the basis of the respective spectral energy levels of the noisy combined signal and of the referent noise signal; and g) selectively reducing the noise by applying variable gain that is specific to each frequency band and to each time frame.

Abstract: In a method and equipment for operating a voice-supported system, such as a communications and/or intercom/two-way intercom device in a motor vehicle, using at least one microphone and at least one loudspeaker to reproduce a signal generated by the microphone, as well as a bandpass filter configured between the microphone and the loudspeaker, a power of the signal as a function of a frequency is determined, and the bandpass filter is adjusted as a function of at least one local maximum of the power of the signal as a function of the frequency.

Abstract: A method for reducing audible noise in a vehicle audio component includes steps of: determining that the audio component is or is about to be operating in a susceptible mode wherein it is likely to receive electrical interference caused by an electrical component operating in an interfering operating state; communicating to the electrical component that the audio component is operating in the susceptible mode; and changing operation of the electrical component from the interfering operating state to a non-interfering operating state less likely to generate electrical signals causing audible noise.

Abstract: An echo cancelling algorithm in a communication device initializes a step size value used in an adaptive echo filter based on a background noise signal power level relative to a power level of a received signal and a power level of an echo estimate relative to an output of an echo canceller. The algorithm then adjusts the step size value. One aspect adjusts the step size based on the detection of large fast fourier transform values at one, or more, disturbing-signal frequencies. Another aspect estimates residual echo energy to adjust an estimated echo energy, which then is used to set a double talk flag if a transmit signal has much more power than the estimated echo signal. Another aspect compares transmit signal power to a decimated version of the transmit signal power and sets the double talk flag if the former exceeds the latter by a predetermined amount.

Abstract: Active noise control system and method for controlling an acoustic noise generated by a noise source at a listening location, in which system and method sound is picked up in the surroundings of the listening location by a sound sensor; an electrical noise signal which corresponds to the acoustic noise of the noise source is generated and filtered adaptively in accordance with control signals. The adaptively filtered noise signal is irradiated into the surroundings of the listening location by a sound reproduction device, where a secondary path transfer function extends between the sound reproduction device and sound sensor. The noise signal is filtered with a transfer function that models the secondary path transfer function. The signals which are provided by the sound sensor after first filtering serve as control signals for the adaptive filtering.

Abstract: An active vibratory noise control apparatus includes a basic signal generator configured to output a basic sine wave signal and a basic cosine wave signal. An adaptive finite impulse response filter is configured to output a control signal to cancel the vibratory noise. A vibratory noise cancelling device is configured to generate vibratory-noise canceling sound. An error signal detector is configured to output an error signal. A reference signal generator is configured to output a reference signal and corrects the basic cosine wave signal and the basic sine wave signal based on correction values. A buffer is configured to accumulate a number of reference signals corresponding to a number of taps of the adaptive finite impulse response filter. A filter coefficient updating device is configured to sequentially update filter coefficients of the adaptive finite impulse response filter to minimize the error signal.

Abstract: An active noise/vibration/sound control system for a vehicle has an ANC (active noise control apparatus), an AVC (active vibration control apparatus), and an ASC (active sound control apparatus). To prevent the ANC, the AVC, and the ASC from interfering with each other and hence to prevent vehicle cabin environment of vibrations, noise, and sound from being impaired, activation and inactivation of the ANC, the AVC, and the ASC are controlled or their control characteristics are controlled in relation to each other by a weighting variable calculator as a coordination controller, depending on an engine rotation frequency and a frequency change which are representative of a running state of the vehicle as detected by an engine rotation frequency detector and a frequency change detector that serve as a running state detector.

Abstract: Gain characteristics depending on the frequency of a reference signal from speakers to a passenger position in a motor vehicle, i.e., gain characteristics which are an inversion of vehicle cabin sound field characteristics, are set in a first acoustic corrector. At the passenger position, a gain characteristic curve that is flat at various frequencies is achieved to prevent gain peaks and dips from occurring at the passenger position. A sound effect generated at the passenger position is made linear depending on the state of a noise source, or more specifically, a noise source caused by an accelerating action on the motor vehicle.

Abstract: A cosine wave over one period is stored as waveform data in a memory, and address shift values based on a phase lag in transfer characteristics from a speaker to a microphone are stored in a memory. An address shift value is read from the memory by referring to the frequency, and waveform data are read from the memory at addresses that are produced by shifting the addresses from which the reference cosine wave signal and the reference sine wave signal are read, by the address shift value. The read waveform data are used as a first reference signal and a second reference signal, which are applied to adaptive notch filters, to suppress vibratory noise.

Abstract: A digital sound processing system suitable for use in a vehicle includes an interior rearview mirror assembly having a mirror casing having a reflective element disposed thereat. The interior rearview mirror assembly includes at least one microphone, with the microphone located at one of a rear portion of the mirror casing, a bezel portion of the mirror casing, a side portion of the mirror casing, an upper portion of the mirror casing, and a lower portion of the mirror casing. The microphone generates at least one signal indicative of a vocal input with vehicle cabin noise included therewith. A digital signal processor processes the signal and provides an output signal with reduced vehicle cabin noise.

Abstract: A vehicle has an electric drive mode, a body defining a vehicle interior, a first and second set of audio speakers positioned outside and inside of the interior, respectively, and a controller. The controller generates an acoustic signal, broadcasts the acoustic signal via the first set of speakers during an electric drive mode, and generates and broadcasts a cancelling signal via the second set of speakers. The broadcasts are coordinated to substantially cancel an attenuated portion of the acoustic signal resulting from propagation of the acoustic signal into the interior. A method cancels a synthesized sound within a vehicle interior by collecting vehicle operating values, generating an acoustic signal as the synthesized sound during an electric drive mode, and processing the acoustic signal to generate a modified acoustic signal approximating an attenuated portion of the acoustic signal propagating into the vehicle interior.

Abstract: A method of and a system for detecting a person occupying a vehicle seat or a corresponding underlay whereby the underlay is provided with a single dynamic sensor and whereby the measurement signal is compared with a reference signal in comparing means, wherein the system comprises first measuring means for measuring a first measurement signal in a first frequency band representing a signal for human presence, and second measuring means for measuring the reference signal as a second measurement signal in a second frequency band representing a signal for background noise, comparing means for indicating an occupancy, wherein the signal strength in the first measurement signal in the first frequency band of human presence signal domination is compared to the signal strength in the reference signal in the second frequency band where essentially only background noise exists.

Abstract: An active noise control system prevents a continuous muffled sound from being generated as an abnormal sound under a high sound pressure from a speaker when a microphone as a sound detector is covered, and reduces noise immediately when the microphone is uncovered. A first threshold value as an upper limit value and a second threshold value as a lower limit value are provided for the filter coefficient of an adaptive notch filter. When the filter coefficient is greater than the first threshold value, a control sound is faded out according to a forgetting process. When the filter coefficient is smaller than the second threshold value, an adaptive control process is resumed. Even if the microphone is covered, the filter coefficient does not exceed the first threshold value as the upper limit value.

Abstract: A method of controlling noise from a six cylinder engine that can selectively use in separate operating modes either three cylinders, four cylinders, or all six cylinders, is provided that uses a noise cancellation system to provide a cancellation sound at a first frequency representative of the engine operating mode. When the vehicle changes, for example, from a three cylinder utilization mode to six cylinder utilization mode, the method extends the provision of the noise cancellation sound, at a frequency representative of three cylinder operation, beyond the time when three cylinder mode is changed to six cylinder mode. As a result, a residual “pop” noise associated with the vehicle exhaust, that is traditionally heard during the transition period is cancelled and no longer noticeable. The method also includes implementation of a waiting time before a providing cancellation sounds of different frequencies, to avoid amplitude mismatch.

Abstract: While a vehicle incorporating an active vibration noise control apparatus is decelerating, hysteresis is given if an operating point moves from an operating point on a sampling period characteristic curve to an operating point on another sampling period characteristic curve. Even if a base period detected depending on noise contains fluctuations, a smooth noise control process is performed. Since a division number produced when the base period is divided by a sampling period is a real number, the freedom of design is widened. Less strict limits are posed on the processing capability of a CPU of the active vibration noise control apparatus to provide a wider control range.

Abstract: An active noise control system generates an anti-noise signal to drive a speaker to produce sound waves to destructively interfere with an undesired sound in a targeted space. The speaker is also driven to produce sound waves representative of a desired audio signal. Sound waves are detected in the target space and a representative signal is generated. The representative signal is combined with an audio compensation signal to remove a signal component representative of the sound waves based on the desired audio signal and generate an error signal. The active noise control adjusts the anti-noise signal based on the error signal. The active noise control system converts the sample rates of an input signal representative of the undesired sound, the desired audio signal, and the error signal. The active noise control system converts the sample rate of the anti-noise signal.

Abstract: A noise reduction device, including a microphone for detecting noise, a noise controller for reversing the phase of noise detected by the microphone based on information outputted from the microphone, and a speaker for outputting sound based on information outputted from the noise controller, is arranged at a seat surrounded by a shell portion having a cavity, wherein a speaker is disposed in the cavity of the shell portion.

Abstract: A method for attenuating the low-frequency noise generated at the outlet (18) of an exhaust line (14). A signal representing the noise to be attenuated is defined; a first high-frequency acoustic wave (F1) is emitted from a first transducer (22) into an attenuation region (26) of the exhaust line (14), the first acoustic wave having a carrier frequency higher than 50 kHz; and a second high-frequency acoustic wave (F1+?fcb) is emitted by a second transducer (24) into the attenuation region (26) of the exhaust line, the second acoustic wave having the carrier frequency of the first high-frequency acoustic wave (F1) and containing a low-frequency counter-noise signal (?fcb) which is out of phase with the signal representing the noise to be attenuated.

Abstract: The present invention provides a method, apparatus, and computer implemented instructions for computer-based onboard noise suppression devices with remote web-based management features. The present invention detects noise within a computer. A noise canceling signal is generated based on parameters. These parameters may include, for example, the percentage of noise to suppress. The noise canceling signal is broadcasted to reduce or eliminate noise. Additionally, the present invention provides the ability to remotely manage noise suppression within computers.

Abstract: A method for reducing noise in a vehicle by reducing under certain conditions the rotational speed of certain rotational components.

Abstract: There is provided an entertainment system comprising at least one seat, an electronic unit (100) for active noise reduction in the seat and at least one headphone (300). The headphone has an electro-acoustic reproduction transducer (310), a microphone (330) for recording interference signals and an adjusting unit (320) having an active filter for correcting a frequency response characteristic of the output signal of the microphone, for performing pre-filtration for active noise reduction and for the output of a corrected and filtered signal. The electronic unit (100) performs active noise reduction based on the corrected and filtered signal of the adjusting unit (320).

Abstract: A system and method for detecting a sound originating from a body and enhancing signal-to-noise ratio with respect to noise originated outside the body is disclosed. The system comprises a light source for producing a quasi-monochromatic, spatially-coherent light beam; and interferometer for interfering alight beam originated from the source, incident upon the body and reflected from it, with a reference beam, which also originates from the light source; and a detector for detecting changes caused by motion of a least one interference fringe across the detector, and for generation a corresponding electric signal.

Abstract: System including signal processor in communication with sound detector and with sound-emitting device. Sound detector and sound-emitting device are in audio communication with occupant compartment. Signal processor is configured for receiving input signal from sound detector being indicative of background audio noise in occupant compartment, and for causing sound-emitting device to emit output sound that partially cancels background audio noise in manner responsive to received input signal. Another system, including array of sound detectors and array of sound-emitting devices. Method includes providing signal processor in communication with sound detector and sound-emitting device, where sound detector and sound-emitting device are in communication with occupant compartment. Further in method, signal processor is caused to receive input signal from sound detector being indicative of background audio noise in occupant compartment.

Abstract: A noise reduction device including a noise detection microphone including a high-frequency noise detection microphone and a low-frequency noise detection microphone for respectively detecting a high-frequency noise and a low-frequency noise generated from a noise source; a noise control unit for generating a control sound signal for cancelling a noise detected by the noise detection microphone in a control center of control space; and a loudspeaker for outputting a control sound based on the control sound signal from the noise controlling unit. The high-frequency noise microphone is disposed in a vicinity of a head portion of a user in a state in which directivity in an opposite direction with respect to the control center is added, and the low-frequency noise detection microphone is disposed outside of a sound-insulating wall.

Abstract: A method of tuning a hands-free system in a mobile vehicle, the method including receiving a plurality of vehicle condition inputs, creating a noise parameter based on the vehicle condition inputs and adjusting a noise suppression algorithm of the hands-free system based on the created noise parameter.

Abstract: An active vibratory noise control apparatus reduces vibratory noise which is produced in the passenger compartment of a vehicle based on vibratory noise generated by a variable-cylinder internal combustion engine that can selectively be operated in a full-cylinder operation mode in which all of the cylinders are operated and a partial-cylinder operation mode in which some of the cylinders are out of operation. The active vibratory noise control apparatus has a partial-cylinder operation mode determining circuit for determining whether the variable-cylinder internal combustion engine is in the partial-cylinder operation mode or not. Depending on a determined result from the partial-cylinder operation mode determining circuit, a transistor is turned on or off to switch an amplifying circuit which drives a speaker into and out of operation.

Abstract: An active noise reducing device includes switchover frequency memory which stores a speaker having weaker influence of level drop or dips in gain characteristics of transmission from first speaker and second speaker both working as secondary noise generators to microphone working as a residual signal detector, and also stores a frequency band of that speaker. Output switcher appropriately and selectively switches first speaker over to second speaker in response to the noise frequency at present calculated based on the rpm of engine by frequency calculator. This structure allows the active noise reducing device to work steadily even if level drop or a dip occurs in the gain characteristics of transmission from the speaker to the microphone, and allows suppressing the occurrence of abnormal sound due to divergence or distorted sound due to excessive output. Ideal noise reduction effect can be expected.

Abstract: A microphone assembly includes one or more transducers positioned in one or more housings. A processing circuit is coupled to the transducer for outputting an electrical signal such that the microphone in combination with the processing circuit very effectively cancels noise. The microphone assembly can be employed in a vehicle accessory.

Abstract: A system for countering ambient noise when operating an address system in at least one compartment of a passenger transport unit includes: (a) a noise control unit; and (b) at least one memory unit coupled with the noise control unit. The at least one memory unit stores noise characteristic information relating with at least one operational condition of the transport unit. The noise control unit employs the noise characteristic information to effect the countering.

Abstract: An electromechanical converter has independent electric input sections. The output of an active noise reduction controller is inputted into an electric input section and the audio signal from an audio section is inputted into an electric input section. These are mechanically combined at a vibration section and the combined signal is radiated as a sound wave into the space. With such a structure, both the active noise reduction function and the audio reproduction function are realized without installing a large device in an existing audio reproduction apparatus.

Abstract: An apparatus for reducing baffle vibration includes a baffle that is subject to vibration. A first transducer that is seated in the baffle includes a first diaphragm that is acoustically coupled to a listening area in a vehicle and also acoustically coupled to a cavity in the vehicle. A first input signal applied to the first transducer causes the first diaphragm to move in a first direction, thereby generating an acoustic output. A second transducer is mechanically coupled to the first transducer. The second transducer includes a second diaphragm that is acoustically coupled to the first diaphragm and also acoustically coupled to the listening area. A second input signal applied to the second transducer causes the second diaphragm to move in a second direction that is substantially opposite to the first direction to reduce a vibration imparted to the baffle while substantially maintaining the acoustic output.

Abstract: The invention concerns a listening device (1) for transmitting electroacoustic signals comprising an earphone (2) and means for connecting said earphone (2) with a remote electroacoustic source (3). The invention is characterized in that it comprises an acoustic filter (4) and that its shape is perfectly adapted to the external auditory canal of the ear so as to provide sufficient soundproofing to the external environment. The invention also concerns a headphone comprising one or two such listening devices.

Abstract: An active noise controller can determine the signal transmission characteristics from the power amplifier and the speaker to the microphone without using any special external measuring instrument and calculate a cosine correction value and a sine correction value without using an external computer. The active noise controller uses the cosine correction value and the sine correction value to actively reduce vibrational noise. The measurement mode is selected on touch panel (3), and correction value calculator (22) calculates cosine correction value C0 and sine correction value C1 by using filter coefficients W0 and W1 which allow error signal e?(n) to approach zero. Memory (23) stores these values C0 and C1.

Abstract: A noise reduction system for actively blocking a noise source for a means of transport. The noise reduction system comprises at least one counter sound source and at least one intensity sensor. The at least one counter sound source and the at least one intensity sensor are arranged in a measuring region. In the measuring region, measuring of the noise intensity of the noise source and measuring of the counter sound intensity of the counter sound source are by the intensity sensor. Based on the measured noise intensity and the counter sound intensity, the counter sound source is controllable such that the sound energy input of the noise source can be globally reduced by the counter sound source.

Abstract: In a sound field control apparatus including multiple speakers, multiple microphones gathering sound radiated from the multiple speakers, a mode decomposition filter that performs mode decomposition on a sound pressure distribution, and a control filter that controls the input signals to be input to the multiple speakers such that the mode amplitudes of the modes decomposed by the mode decomposition filter can have a predetermined value, a sound pressure distribution in the acoustic space is measured, and the sound pressure distribution in the acoustic space is expressed by using a sinusoidal function and cosine function of a space frequency of the mode to be controlled in amplitude. The mode space frequency is corrected such that the expressed sound pressure distribution can be equal to the measured sound pressure distribution, and the filter coefficient for the mode decomposition filter is determined based on the mode space frequency obtained by the correction (corrected mode space frequency).

Abstract: A digital sound processing system suitable for use in a vehicle comprises an interior rearview mirror assembly that includes at least a first microphone and a second microphone. The first microphone generates a first signal indicative of a vocal input with vehicle cabin noise included therewith and the second microphone generates a second signal indicative of a vocal input with vehicle cabin noise included therewith. A digital signal processor is provided that processes the first signal and the second signal and that provides an output signal with reduced vehicle cabin noise. The digital signal processor preferably comprises a microprocessor executing at least one million instructions per second.

Abstract: An engine sound control apparatus capable of arranging a sound of a frequency that is lower than the fundamental-order frequency of the engine. The engine sound control apparatus detects the frequency of the engine sound and generates a sound signal of a frequency that is in accordance with a control signal and outputting the sound signal generated by the oscillator. Through the interaction between the sound generated by the apparatus and the engine sound, occupants in the passenger compartment will perceive a sound of a frequency that is equal to the difference between the generated sound and the fundamental-order sound. This yields a sound that is lower in frequency than the fundamental-order sound without actually generating a sound of a frequency that is lower than that of the fundamental-order sound.

Abstract: In an active noise cancellation system having an adaptive filter that outputs a control signal, first and second speakers that emit a canceling signal generated based on the control signal, a microphone that detects an error signal, a correction filter that corrects the base signal by a correction value to generate a reference signal and a filter coefficient updater that successively updates the adaptive filter coefficient based on the error signal and reference signal such that the error signal is minimized, the correction value of the correction filter is set to a sum obtained by adding the transfer characteristic from the first speaker to the microphone, and a product obtained by multiplying the transfer characteristic from the second speaker to the microphone by the prescribed value, thereby enabling to reduce the number of microphones and avoid the increase in parts, the amount of work to provide complicated wiring to the microphones, and the computational load involved in updating the adaptive filter co

Abstract: An acoustic system uses a self speaker installed to be at the back of a listener in a first individual space and an error microphone installed to be closer to the listener than the self speaker. A sound-leakage reduction filter generates control sound for negating sound leaked from another speaker installed in a second individual space to the first individual space, and provides the control signal to the self speaker. A virtual sound-source filter generates a virtual sound source, and a rear-sound-source inverse filter corrects rearward localization of a sound image toward the listener.

Abstract: A speech correction apparatus includes a speaker for generating guidance speech; a microphone set at a hearing position; an acoustic-characteristic setting unit for separating ambient noise from the guidance speech at the hearing position; an operating unit; a speech correcting filter for correcting the sound pressure level of the guidance speech generated by the speaker based on the average power of the guidance speech and the average power of the ambient noise which are separated; a loudness-compensating-gain calculating unit; and a speech-head correcting unit for correcting the average power of the guidance speech corresponding to the speech head at the border between a silent state and a speech state of the guidance speech.

Abstract: Microphone is arranged at an evaluation point at the front seat; a signal for controlling vibration noise at this position is sent out from speaker at the front seat; secondary sound for canceling an influence of secondary sound at the front seat on the rear seat is sent out from speaker at the rear seat; microphone is arranged at an evaluation point at the rear seat; a signal for controlling vibration noise at this position is sent out from speaker; and secondary sound for canceling an influence of secondary sound at the rear seat on the front seat is sent out from speaker at the front seat.

Abstract: A subtractor subtracts a first control signal output from a first bandpass filter from an error signal, and supplies a differential signal to a second bandpass filter. The second bandpass filter, which has a central frequency of 70 Hz, is affected by an operation of the first bandpass filter, i.e., a first control signal, which has a central frequency of 40 Hz. The first bandpass filter is not affected by an operation of the second bandpass filter, i.e., the second control signal.

Abstract: A vehicular active vibratory noise control apparatus includes an adaptive notch filter (second control signal generating unit) for generating a corrected error signal representative of a road noise only by removing the component of a rotational frequency (the component of an engine muffled sound) from an error signal, generates a first control signal from the corrected error signal and a reference signal, and reduces the component of the rotational frequency (engine muffled sound) at a position where a microphone is located (evaluating point).

Abstract: The present invention provides an active control type noise reducing device that is disposed at a sound barrier and with which can be obtained an excellent noise reduction effect with respect to moving sound sources. Linear array of flat loudspeakers are arranged in ascending order from an incoming side of automobiles towards an outgoing side. Delay times of 0, ?, 2?, . . . , 8? are respectively given in the arrangement order to the linear array of flat loudspeakers. By delaying signals in correspondence to the arrangement order, the wavefront of a control sound can be slanted in a diagonal direction. Namely, “line sound sources”, where sound sources are linearly arranged, arc pseudo-realized.

Abstract: A system and method for enhancing the sound signal produced by an audio system in a listening environment by compensating for ambient sound in the listening environment, comprises producing an audio sound in the time domain from an electrical sound signal in the time domain. The electrical sound signal in the time domain is transformed into an electrical sound signal in the frequency domain and the electrical sound signal in the frequency domain is retransformed into an audio sound in the time domain. The total sound level in the environment is measured and a signal representative thereof is generated. The audio sound signal and the total sound signal are processed to extract a signal representing the ambient sound level within the environment, and equalization is performed in the frequency domain to adjust the output from the audio sound signal to compensate for the ambient noise level.

Abstract: An in-vehicle communication system includes a control unit which locates coupling points of each one of active speaker units to in-vehicle network. The plurality of the active speaker units includes a plurality of acoustic characteristics set data and programs for determining their own addresses. The respective active speaker units thus can be coupled to in-vehicle network without changing their software, and acoustic characteristics values in response to their coupling points in the vehicle can be established.

Abstract: The present invention relates to a method for processing sound signals in a vehicle multimedia system. A sound signal is recorded by a microphone. A voice signal component resulting from reproducing a voice signal and an audio signal component resulting from reproducing an audio signal are compensated in the recorded sound signal. The invention further relates to a system for processing sound signals and a vehicle multimedia system.

Abstract: A noise control device according to the present invention comprises: four or more noise detectors each for detecting a plurality of noises arriving thereat, and outputting the noises as a noise signal; a control speaker for radiating, to a control point, a control sound based on each noise signal; and a filter section for signal-processing noise signals from the noise detectors by using filter coefficients which respectively correspond to the four or more noise detectors and which are set such that the control sound from the control speaker reduces the plurality of noises arriving at the control point, and for adding up all the signal-processed noise signals, and for outputting a resultant signal to the control speaker. The control point and the control speaker are provided within a polyhedral-shaped space whose apexes are placement positions of the noise detectors.

Abstract: New and improved electroacoustic devices each including at least one transducer assembly having one or more microphones typically mounted on a baffle plate and disposed in substantially the same acoustic plane as a speaker or speakers. In the various embodiments, at least one microphone and at least one speaker face the same or opposite directions. Each microphone may be parallel to or oriented at an angle with respect to the speaker. In other embodiments, the speaker includes a central opening or cavity in which a microphone having one of various orientations is provided. The orientations of the microphone or microphones with respect to the speaker or speakers minimize adverse noise reduction effects associated with the differences in sensitivities, frequency responses and phase responses and acoustic time delays between the microphones and the speaker or speakers, as well as minimize sound reflections that are picked up by the microphone or microphones.

Abstract: A frequency detecting circuit estimates the frequency fp of a propeller shaft based on the frequency fc of vehicle speed pulses, and calculates a control frequency fp? which is a harmonic of the frequency fp. A basic signal generator generates a basic cosine wave signal xp1 and a basic sine wave signal xp2 of the control frequency fp?. Adaptive filters and an adder generate a control signal Scp for canceling a driveline noise produced in a passenger compartment by the propeller shaft. A speaker outputs a canceling sound based on the control signal Scp into the passenger compartment.