Active silencer

Details Active silencer Active silencer

1987-07-07

1989-02-21

Fuller, B. R.

Acoustics

Sound-modifying means

By wave interference

381 71, F01N 106

Patent

active

048057339

ABSTRACT:
An active silencer provided in a pipe which has one end reaching the noise source and the other end open, the active silencer being provided with a sound generating means which is provided at the sidewall of the pipe facing inside the pipe, a sound collecting means which is provided outside the pipe close to the other end and which detects noise dissipated from the pipe opening, a phase leading means which outputs a lead phase output signal which is advanced from the phase of an output signal of the sound collecting means by a phase corresponding to a predetermined time determined by the distance between the sound generating means and the sound collecting means; and a drive means which outputs a signal constituting the lead phase output signla inverted in phase as a drive signal for the sound generating means, the predetermined time .tau. being set so that .tau.=L/C, wherein the distance between the sound generating means and the sound collecting means is L and the speed of sound is C.

REFERENCES:
patent: 2043416 (1936-06-01), Lueg
patent: 3936606 (1976-02-01), Wanke
patent: 4025724 (1977-05-01), Davidson et al.
patent: 4122303 (1978-10-01), Chaplin et al.
"Phase Locked Loop, Linear Integrated Circuits, SE565 NE565" Signetics Corporation, USA, 1970.
Method of Use of PLL-IC by M. Hata and K. Furukawa, pp. 21 to 26, Sangyo Hochi Center, 1970 (in Japanese).

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