Honda Giken Kogyo Kabushiki Kaisha

Matsushita Electric Industrial Co., Ltd.

Matsushita Denkisangyo Kabushiki Kaisha

Honda Giken Koygo K.k.

Hisashi Sano

Toshio Inoue

Akira Takahashi

Hiroyuki Hashimoto

Kenichi Terai

Isao Kakuhari

Tsuyoshi Yamashita

Hideshi Sawada

Yoshio Nakamura

Shuichi Adachi

Takayuki Tsuji

Makoto Namekawa

Toshihiko Ohashi

Masaichi Akiho

Akira Suto

Kunio Miyauchi

Hideki Kasuya

Tetsu Kanamori

Hideki Sato

Sou Nakamura

Kenji Imai

Syunichi Imanishi

An active noise control system is capable of canceling out noise in the passenger compartment of a vehicle based on low-frequency road noise. The active noise control system has a feed-forward control unit for being supplied with reference signals highly correlated to noise from a noise source and generating a noise cancellation signal which is out of phase to noise in the passenger compartment of the vehicle, and a canceling sound generating unit disposed in the passenger compartment for generating a noise canceling sound in response to the noise cancellation signal from said feed-forward control unit. The active noise control system also has microphones for generating reference signals which are positioned respectively near the base of the front seat, near the center of a roof, and within a trunk compartment, i.e., respectively at vibrational antinodes of a primary or secondary acoustic normal mode of the passenger compartment in the longitudinal direction thereof. Output signals from the microphones are supplied as the reference signals.

Active noise control system

An active noise control system for reducing road noise of low frequency generated inside the cabin of a vehicle is provided. The active noise control system includes a noise detector, a signal generator for processing the input noise signal to generate a signal for producing noise canceling waves, a limiting amplifier having a specified threshold value for variably amplifying the processed signal so that the amplitude of output signal will not exceed the threshold value, and an electrical acoustic converter for producing noise canceling acoustic waves in accordance with the output signal.

In an active noise control apparatus in which an audio signal and a noise control signal are mixed to thereby sound a loudspeaker inside a motor vehicle, a general-purpose audio head unit cannot conventionally be freely changed for the one already mounted on the motor vehicle. As a solution, an active noise control unit is provided with a buffer amplifier and a mixer. An audio signal amplified by a power amplifier in an audio head unit is adjusted in level by the buffer amplifier such that a level of an audio signal outputted after amplification by the first amplifier becomes substantially equal to a level of the audio signal outputted from the audio head unit. Then, at the mixer, a noise control signal outputted from an active noise controller is added to an audio signal outputted from the buffer amplifier. Therefore, any audio head unit can be freely changed for the one already mounted on the vehicle as long as the audio head unit contains therein a power amplifier.

Vehicle-mounted noise control apparatus

A vibration/noise active control system for automotive vehicles which generates a canceling signal for canceling vibrations and noises generated within the compartment of the vehicle, based on a reference signal related to the vibrations and noises by means of an adaptive filter. The canceling signal is converted into a canceling sound. The adaptive filter has a filter coefficient thereof changed based on the cancellation error between the canceling sound and the vibrations and noises within the compartment, detected by an error sensor, and the reference signal. A memory stores a plurality of filter coefficient values of the adaptive filter corresponding to a plurality of predetermined traveling conditions of the vehicle. A discriminator reads out a filter coefficient value of the adaptive filter corresponding to the detected predetermined traveling condition of the vehicle, supplies the read-out filter coefficient value to the adaptive filter to generate the canceling signal, and stores a filter coefficient value of the adaptive filter which has been changed based on the generated canceling signal.

Vibration/noise active control system for vehicles

An active vibration controller includes acceleration detectors for generating output signals on the basis of vibrations of a vehicle, speakers provided in a vehicle's cabin, microphones provided in the vehicle's cabin for receiving generated sounds from the speakers and road noises generated on the basis of running of the vehicle, and adaptive digital filters using output signals from the acceleration detectors as inputs for controlling filter factors on the basis of an RLS algorithm to minimize levels of output signals from the microphones in response to output signals from the microphones and output signals from the acceleration detectors through use of a transfer function matched to the transfer function of the vehicle's cabin in a sound field between the speakers and the microphones. The controller minimized levels of output signals from the microphones by developing an applied output signal to the speakers. Thus parameters of the filter factors are adaptively updated in accordance with identified system characteristics, providing satisfactory estimation accuracy, and quick convergence to changed sensed noise to silence road noise in the vehicle's cabin.

Active vibration controller

A reproduced sound is sent from a speaker as a sound source unit provided in a sound field. An error signal is produced by a microphone on the basis of a difference in sound between the reproduced sound from the speaker and noise coming from the outside of the sound field into the sound field. A digital filter has a fixed transfer function approximated to a transfer function of the sound field, to which a signal for driving the speaker is supplied. Variation of the transfer function of the sound field is detected by the digital filter. A difference signal between the error signal and an output signal from the digital filter is calculated by an adder. The difference signal determined by the adder is inputted into an IMC filter. A signal for compensating the variation of the transfer function of the sound field and variation of the noise is produced by the IMC filter. A variable parameter of the IMC filter is set so that an absolute value of a product of a value of an approximated and set amount of variation, a distance from the sound source unit to the error-detecting unit, and the variable parameter of the IMC filter is less than 1. Thus, the noise coming into the inside of the sound field is canceled by using an output sound of the speaker.

Active noise-suppressive control method and apparatus

An adaptive control circuit is responsive to a reference signal, i.e. an output from a sensor which senses vibration from a vibration source, for generating a cancelling signal having a transfer characteristic inverse to a transfer characteristic of vibration from the vibration source to a human body. A loud speaker is responsive to an output from the adaptive control circuit for generating cancelling vibration. A microphone senses an error between the vibration from the vibration source and the cancelling vibration from the loud speaker and generates an error signal indicative of the sensed error. The adaptive control circuit varies the inverse transfer characteristic by an amount corresponding to the error signal so as to minimize the above error. A divided processing circuit divides the output from the sensor into vibration components falling respectively within a plurality of frequency ranges and separately processes the divided vibration components. The divided processing circuit has a sampling circuit which samples the divided vibration components at different sampling periods between the above frequency ranges.

Active vibration control system

A noise-canceling method for simultaneously canceling a plurality of harmonic components of the engine rotational speed contained in engine noise. Reference signals are generated in correspondence with a plurality of harmonic components, and an adaptive signal processing is executed by using each reference signal, a composite-sound signal of the engine sound and a composite noise-canceling sound at a noise-canceling point, thereby generating a noise-canceling signal. The noise-canceling signal is input to a speaker. The reference signal corresponding to a harmonic component of a low level is multiplied by a constant K before it is input to the speaker so as to approximately equalize the levels of all the harmonic components at the noise-canceling point.

Noise canceling method

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Utsunomiya, Japan

Hisashi Sano