Noise canceling system
First Claim
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1. A noise canceling system for an air distribution structure comprising:
- duct means for delivering air;
a source of noise located with respect to said duct means so as to transmit noise into said duct means as a forward component which is subject to reflection due to coaction with said duct means to produce a reflected component whereby noise from said source of noise can be present in said duct means as both a forward component and a reflected component;
sensing means located in said duct means;
said sensing means includes a pair of sensors in a spaced relationship along said duct means relative to said source of noise;
noise canceling means located with respect to said duct means so as to transmit a canceling noise into said duct means;
circuitry connected to said sensing means and said noise canceling means and including means for distinguishing between said forward component and said reflected component and for producing an output representative of only said forward component and means for driving said noise canceling means so as to produce noise corresponding only to said forward component.
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Abstract
Two microphones spaced along a duct of an air conditioning system provide inputs to circuitry whereby the noise being generated is distinguished from reflected noise. The circuitry imposes a time delay corresponding to the time required for generated noise to pass from the upstream microphone to a canceling speaker. The canceling speaker is driven by the circuitry, subject to the time delay, such that noise at the speaker is canceled by the appropriately driven speaker. In a preferred embodiment movement of the speaker is sensed whereby the actual sound being produced can be compared with the sound required by the canceling speaker driving signal.
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Citations
14 Claims
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1. A noise canceling system for an air distribution structure comprising:
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duct means for delivering air; a source of noise located with respect to said duct means so as to transmit noise into said duct means as a forward component which is subject to reflection due to coaction with said duct means to produce a reflected component whereby noise from said source of noise can be present in said duct means as both a forward component and a reflected component; sensing means located in said duct means; said sensing means includes a pair of sensors in a spaced relationship along said duct means relative to said source of noise; noise canceling means located with respect to said duct means so as to transmit a canceling noise into said duct means; circuitry connected to said sensing means and said noise canceling means and including means for distinguishing between said forward component and said reflected component and for producing an output representative of only said forward component and means for driving said noise canceling means so as to produce noise corresponding only to said forward component. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification