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Patent US4965832A successfully refreshed from Google Patents.
US4965832A
Expired / Lapsed
US
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Active noise control
Assignee: The General Electric Company PLC
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Filing: 1989-04-25
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Granted: 1990-10-23
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Expires: 2009-04-25
Abstract
Abstract An active noise control system for controlling noise propagated through a duct comprises a first microphone located to receive the propagated noise at a point in a plane perpendicular to the length of the duct. A loudspeaker is located substantially at that plane for introducing sound into the duct. An analog first control circuit is operative in response to the noise received by the first microphone to feed a signal to the loudspeaker such that the sound introduced thereby destructively interferes with the noise at that point. A second microphone is located further downstream to receive residual noise propagated along the duct despite the destructive interference. A second control circuit, responsive to the residual noise received by the second microphone, controls parameters of the analog first control circuit so as to minimize the residual noise. In particular, the first control circuit includes an integrator which has a transfer function which is electrically controlled by the second control circuit.
Inventors
- 👤 John W. Edwards
- 👤 Nicolaas M. J. Dekker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 15:17
CPC Classifications
G; G10; G10K; G10K11/00; G10K11/16; G10K11/175; G10K11/178; G10K11/1785; G10K11/17853; G10K11/1781; G10K11/17813; G10K11/17819; G10K11/17857; G10K11/1787; G10K11/17879; G10K11/17881; G10K2210/00; G10K2210/10; G10K2210/112; G10K2210/30; G10K2210/301; G10K2210/3013; G10K2210/3028; G10K2210/3034; G10K2210/3045; G10K2210/321; G10K2210/3217; G10K2210/50; G10K2210/506
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
190 words
An active noise control system, comprising: (a) a duct through which noise to be controlled can propagate from a noise source; (b) first receiving transducer means located to receive the propagated noise at a point in a plane perpendicular to the length of the duct; (c) transmitting transducer means located substantially at said plane for introducing sound into the duct; (d) analog first control means connected in a feedback loop with said first receiving transducer means and said transmitting transducer means and operative, in response to the noise received by said first receiving transducer means, for feeding a signal to the transmittng transducer means such that the sound introduced thereby destructively interferes with the noise at said point, said first control means including integrating circuit means having an electrically-controllable transfer function; (e) second receiving transducer means located further from the noise source than said plane to receive residual noise propagated along the duct despite said destructive interference; and (f) second control means, responsive to the residual noise received by said second receiving transducer means, for controlling parameters of said first analog control means so a to minimize said residual noise.
Claim 2
Dependent Claim
190 words
An active noise control system, comprising: (a) a duct through which noise to be controlled can propagate from a noise source; (b) first receiving transducer means located to receive the propagated noise at a point in a plane perpendicular to the length of the duct; (c) transmitting transducer means located substantially at said plane for introducing sound into the duct; (d) analog first control means connected in a feedback loop with said first receiving transducer means and said transmitting transducer means and operative, in response to the noise received by said first receiving transducer means, for feeding a signal to the transmittng transducer means such that the sound introduced thereby destructively interferes with the noise at said point, said first control means including integrating circuit means having an electrically-controllable transfer function; (e) second receiving transducer means located further from the noise source than said plane to receive residual noise propagated along the duct despite said destructive interference; and (f) second control means, responsive to the residual noise received by said second receiving transducer means, for controlling parameters of said first analog control means so a to minimize said residual noise.
Claim 3
Dependent Claim
21 words
A system a claimed in claim 1, wherein said first control means includes an attenuator circuit having an electrically-controllable attenuation factor.
Claim 4
Dependent Claim
27 words
A system as claimed in claim 1, wherein said second control means comprises an analog processor to which analog signals representing the received residual noise are fed.
Claim 5
Dependent Claim
28 words
A system a claimed in claim 1, wherein said second control means comprises a digital data processor to which digital signals representing the received residual noise are fed.
Claim 6
Dependent Claim
36 words
A system as claimed in claim 4, wherein said second control means comprises analog/digital converter means for converting analog signals from said second receiving transducer means into digital signals for feeding to the digital data processor.
Claim 7
Dependent Claim
16 words
A system as claimed in claim 1, wherein said second control means comprises a bandpass filter.
Claim 8
Dependent Claim
16 words
A system as claimed claim 6, wherein said bandpass filter has an electrically-controllable passband centre frequency.
Claim 9
Dependent Claim
21 words
A system as claimed in claim 1, wherein said first control means includes power amplifier means for driving the transmitting transducer.
Claim 10
Dependent Claim
20 words
A system as claimed in claim 1, wherein each of said first and second receiving transducer means comprises a microphone.
Claim 11
Dependent Claim
14 words
A system as claimed in claim 1, wherein the transmitting transducer comprises a loudpspeaker.
References Cited (Backward Citations)
GB1492963A
Cited
GB1548362A
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GB2054999A
Cited
GB2088951A
Cited
GB2147166A
Cited
GB2149273A
Cited
US4677676A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-10-22 | 1994-04-23 | 1994-10-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-10-22 | 1998-04-23 | 1998-10-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-10-22 | 2002-04-23 | 2002-10-23 | $7700.00 | Window Closed / Lapsed |