US 5,293,578 AGranted

Noise reducing device

AssigneeFujitso Ten Limited

InventorsMasaaki Nagami, Akira Motojima, Yoshihiro Kageyama

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Abstract

A noise reducing device including a noise silencing device having a delay unit for delaying a phase of the noise wave, an amplifying unit for adjusting a gain of the delayed noise wave, a superposing unit for superposing the delayed noise wave as the noise silencing wave, a frequency selecting unit for selecting at least one frequency with respect to the noise wave, a factor selecting unit for selecting at least one of a delaying factor used for the delaying unit and a gain factor used for the amplifying unit with respect to the selected frequency, and a controlling unit for controlling at least one of the delaying unit and amplifying unit utilizing the selected delaying factor and a gain factor, respectively, whereby a noise silencing wave having the same frequency and amplitude as that of a noise to reduced but having a reverse phase can be easily obtained, and thus efficient noise reduction can be obtained despite variation of the frequency of the noise.

Claims26

Dependent claims

A noise reducing device in which noise is silenced by superposing on an original noise wave generated from a noise wave source a noise silencing wave having a different phase from that of said noise wave and generated from a noise silencing device, said noise silencing device comprising:

a) a frequency selecting means for selecting at least one frequency with respect to said noise wave, said frequency selecting means having
i) a first and pass filter means comprising a plurality of band pass filters having different pass bands, whereby an electric signal representing said noise wave is separated into a plurality of frequency bands;
ii) detecting means for detecting a frequency band in which a peak level of said noise wave exists;
b) a delaying means for delaying a phase of said noise wave, said delaying means comprising a plurality of delay circuits connected to said band pass filters to delay said separated electric signal;
c) an amplifying means for adjusting a gain of said delayed noise wave, said amplifying means comprising a plurality of amplifying circuits connected to said delay circuits for adjusting the gain to said delayed signal and servicing as a gate circuit;
d) factor selecting means for selecting at least one of a delaying factor used for said delaying means and a gain factor used for said amplifying means with respect to said selected frequency;
e) controlling means for controlling at least one of said delaying means and amplifying means utilizing said selected delaying factor and gain factor, respectively;
f) a processing means for processing at least a signal output from said amplifying circuit to output a noise silencing signal;
and
g) means for superposing said noise silencing signal on said original noise wave.

7 more elements

a delaying means for delaying a phase of said noise wave;
an amplifying means for adjusting a gain of said delayed noise wave;
a frequency selecting means for selecting at least one frequency band having a largest output level from a plurality of frequency bands containing said noise wave;
a parameter memory means for previously storing a plurality of delaying factors, each different from each other, and a plurality of gain factors, each different from each other, said delaying and gain factors being determined with respect to a condition of said noise wave source and connected to said frequency selecting means so that when information about the condition of said noise wave source is output from said frequency selecting means, at least one of said delaying factors and at least one of said gain factors stored in said parameter memory means is selected to control at least one of said delaying means and amplifying means, and
said amplifying means generating a noise silencing wave to be superposed on said original noise wave.

2 more elements

Dependencies are inferred from the claim text.