Other

Hitachi Plant Engineering Construction Co., Ltd.

Hitachi, Ltd.

Nissan Motor Company Limited

Bridgestone Corporation

Tanetoshi Miura

Minoru Takahashi

Hareo Hamada

Takashi Kuribayashi

Keiichiro Mizuno

Noriharu Sato

Akio Kinoshita

Yasushi Yoshimura

Makoto Kohashi

Kinichiro Asami

Akio Akasaka

Yoshitaka Oguri

Haruo Hamada

Hideki Hyoudo

Kaoru Okabe

Ryusuke Gotoda

Takashi Enokida

A method for electrically attenuating a noise in an area for a sound wave to be propagatable in a three dimensional direction by making up a drive signal from the information on the noise and previously given filter coefficients by use of an adaptive digital filter and then generating an additional sound wave in accordance with the drive signal for cancellation of the noise. In the electric noise attenuation method, there are provided in a given region for noise attenuation, first and second error sensor groups for detecting an interference sound wave produced between the noise and additional sound wave, at a sampling time, a filter coefficient is calculated based on the information relating to the first error sensor group, at the next sampling time, another filter coefficient is calculated based on the information relating to the second error sensor group, and these operations are repeatedly executed sequentially for each error sensor to thereby update the filter coefficient of the adaptive digital filter.

Electronic noise attenuation method and apparatus for use in effecting

An electronic noise attenuation system for attenuating a sound wave propagated from a source of noise by generating another sound wave 180.degree. out of phase and having the same sound pressure with the propagated sound wave from electro-mechanic transducer means disposed in a propagation passage of sound waves. In the electronic noise attenuation system, a drive signal for drive the electro-mechanic transducer means is generated in accordance with output signals respectively output from upstream-side and downstream-side mechano-electric transducer means respectively disposed in the propagation passage with the electro-mechanic transducer means therebetween. Namely, the drive signal is created by performing an operation on a difference signal between the output signal of the upstream mechano-electric transducer means and the drive signal according to a given transfer function. Also, the transfer function is determined in accordance with the difference signal and the output signal of the downstream mechano-electric transducer means.

Electronic noise attenuation system

An electronic noise attenuation system for attenuation of non-steady noise occurring in a propagation passage such a duct line by conducting adaptive controls by use of a computer system including a digital filter therein. Sensing microphones M.sub.1, M.sub.2 are located in the propagation passage with a cancellation sound source S therebetween at positions where the transfer functions Hr, Ht of a sound wave generated from the cancellation sound source are equivalent to each other. The output signal of the sensing microphone M.sub.1 and the phase-inverted version of the output signal of the sensing microphone M.sub.2 are input via an add circuit to the control part of the system. The system can prevent the occurrence of an acoustic feedback from the cancellation sound source to the sensing microphone M.sub.1 so as to realize a stable and highly accurate noise attenuation.

An earphone characteristic measuring device comprises an acoustic coupler having an acoustic tube simulated to an external auditory canal in which an earphone under measurement is to be inserted and an acoustic tube of a smaller diameter having an acoustic impedance of approximately 320 ohms connected to an end of the first acoustic tube, a sound source for emitting an impulse sound to the acoustic coupler, a microphone mounted at the end of the first acoustic tube for picking up sound pressure information and a characteristic calculation circuit for transforming an earphone characteristic of the acoustic coupler to an earphone characteristic of a real ear based on an input impedance of the acoustic coupler viewed from an end of the earphone inserted in the acoustic coupler and an input impedance of the real ear represented by a sum of an eardrum impedance of the real ear and an external auditory canal volume of the real ear, stored in a memory in response to the sound pressure information from the microphone. The use of the acoustic coupler of a simple structure facilitates the measurement of a vent characteristic of the earphone and an insertion gain and improves reliability of the measurement.

Earphone characteristic measuring device

Growing community of inventors

Kokubunji, Tokyo, Japan

Tanetoshi Miura