Active noise cancelling apparatus

Electrical audio signal processing systems and devices – Acoustical noise or sound cancellation – Adjacent ear

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G10K 1116

Patent

active

054993016

ABSTRACT:
An active noise cancelling apparatus for actively controlling noise generated by a compressor, where noise is apt to externally leak from an opening portion of a machine chamber storing the compressor driven by an A.C. power supply. The active noise cancelling apparatus includes: a microphone, provided in the vicinity of the opening portion, for detecting noise generated by the compressor; fundamental wave component extracting portion for extracting a fundamental wave component of rotation frequency of the compressor, from a sound signal of the noise detected by the microphone; periodic signal generating circuit for a periodic signal correlative to the fundamental wave component extracted by the fundamental wave component extracting portion; periodic signal outputting circuit for outputting a predetermined periodic signal by means of comparing a phase of the periodic signal generated by the periodic signal generating circuit with a phase of the fundamental wave component; uncancelled sound extracting portion for extracting noise having been not cancelled, excluding the fundamental wave component; sound source waveform generating circuit for forming a harmonics component from the signal outputted by the fundamental wave component extracting circuit; control signal generating circuit for correcting a control signal outputted from the sound source waveform generating circuit, based on a signal from the uncancelled sound extracting portion and for generating the corrected signal in a feedback manner; and a loudspeaker for outputting the control signal generated from the control signal correcting circuit.

REFERENCES:
patent: 4566118 (1986-01-01), Chaplin et al.
patent: 5125241 (1992-06-01), Nakanishi et al.
patent: 5129003 (1992-07-01), Saruta
patent: 5170433 (1992-12-01), Elliott et al.
Saruta et al., "Refrigerator Equipped with Active Noise Control System," International Symposium on Active Control of Sound and Vibration, pp. 509-512 (Apr. 1991).

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