Active noise control
First Claim
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1. An active noise control system for reducing the amount of noise propagated through a duct, comprising:
- a microphone incorporated in a wall of said duct, and operative for detecting the sound of the propagated noise;
a source of anti-sound mounted substantially at the center of a transverse cross-section of said duct; and
a control circuit responsive to the magnitude of the sound detected by the microphone for driving the anti-sound source to substantially suppress first transverse mode excitation in said duct.
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Accused Products
Abstract
An active noise control system for reducing the amount of noise propagated along a duct comprises a microphone mounted in the wall of the duct for detecting the noise, and an active antiphase noise source, such as a loudspeaker, which is mounted substantially in the center of the cross-section of the duct. A control circuit coupled between the microphone and the antiphase noise source includes an integrator having a specific transfer function, which improves the loop gain of the microphone/source loop at low frequencies, and secures stability by altering the phase.
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Citations
8 Claims
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1. An active noise control system for reducing the amount of noise propagated through a duct, comprising:
- a microphone incorporated in a wall of said duct, and operative for detecting the sound of the propagated noise;
a source of anti-sound mounted substantially at the center of a transverse cross-section of said duct; and
a control circuit responsive to the magnitude of the sound detected by the microphone for driving the anti-sound source to substantially suppress first transverse mode excitation in said duct. - View Dependent Claims (2, 3, 4, 5, 6)
- a microphone incorporated in a wall of said duct, and operative for detecting the sound of the propagated noise;
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7. An active noise control system for reducing noise propagated along a duct through which a fluid medium flows, comprising:
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(a) a microphone for detecting the propagated noise; (b) means for mounting the microphone in and flush with a wall of the duct at a substantially calm location where the fluid medium flows at a virtually zero velocity; (c) anti-sound means for radiating sound in an anti-phase relationship with the noise detected by the microphone; (d) means for mounting the anti-sound means substantially at the center of a transverse cross-section of the duct of minimize transverse mode excitation within the duct; and (e) control means operatively connected to the microphone and the anti-sound means, and operative for driving the anti-sound means in response to the noise detected by the microphone to radiate sound which destructively interferes with the propagated noise. - View Dependent Claims (8)
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Specification