Patent US4947356A successfully refreshed from Google Patents.
US4947356A
Expired / Lapsed
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Aircraft cabin noise control apparatus
Assignee: UK Secretary of State for Trade and Industry
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Filing: 1989-02-10
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Granted: 1990-08-07
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Expires: 2009-02-10
Abstract
Abstract In propeller of fan driven aircraft, cabin noise levels may be reduced by adjustment of the phase relationship between a reference propeller or fan and some or all of the other propellers or fans. An aircraft cabin (1) contains four microphones and two loudspeakers which form the active elements of a noise control system. The microphone outputs are fed via amplifiers to a digital signal processor (11) having an adaptation algorithm in a memory store. The processor generates an error signal which is used to adjust the synchrophase angle between the reference propeller and a synchrophased propeller, controlled by a synchrophaser. Thus the synchrophase angle is varied dynamically during flight to minimize propeller noise in the cabin over a range of flying conditions.
Inventors
- 👤 Stephen J. Elliott
- 👤 Philip A. Nelson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 14:17
CPC Classifications
B; B64; B64C; B64C1/00; B64C1/40; B64C11/00; B64C11/46; B64C11/50; G; G10; G10K; G10K11/00; G10K11/16; G10K11/175; G10K11/178; G10K11/1785; G10K11/17853; G10K11/17854; G10K11/17857; G10K11/1787; G10K11/17879; G10K11/17883; G10K2210/00; G10K2210/10; G10K2210/123; G10K2210/128; G10K2210/1281; G10K2210/30; G10K2210/301; G10K2210/3046
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
155 words
Cabin noise control apparatus for an at least two propeller or fan driven aircraft, said apparatus comprising: a plurality of transducers located inside a cabin of said aircraft; a signal processor means for receiving and analyzing signals from said plurality of transducers wherein said signal processor means computes an estimate of the gradient of the sum of the means square outputs of the transducers with respect to the phase relationship θm between a reference propeller or fan and each other propeller or fan and causes the synchrophaser to increment θm by an amount dependent on the value of the gradient in order to minimise the sum of the mean square outputs of the transducers; and a synchrophaser for varying, during flight, the phase relationship between a reference propeller or fan of the aircraft and at least one of the other propellers or fans of the aircraft in response to the output from said signal processor.
Claim 2
Dependent Claim
155 words
Cabin noise control apparatus for an at least two propeller or fan driven aircraft, said apparatus comprising: a plurality of transducers located inside a cabin of said aircraft; a signal processor means for receiving and analyzing signals from said plurality of transducers wherein said signal processor means computes an estimate of the gradient of the sum of the means square outputs of the transducers with respect to the phase relationship θm between a reference propeller or fan and each other propeller or fan and causes the synchrophaser to increment θm by an amount dependent on the value of the gradient in order to minimise the sum of the mean square outputs of the transducers; and a synchrophaser for varying, during flight, the phase relationship between a reference propeller or fan of the aircraft and at least one of the other propellers or fans of the aircraft in response to the output from said signal processor.
Claim 3
Dependent Claim
19 words
Cabin noise control apparatus as claimed in claim 1 wherein at least one of the transducers is a microphone.
Claim 4
Dependent Claim
19 words
Cabin noise control apparatus as claimed in claim 1 wherein at least one of the transducers is an accelerometer.
Claim 5
Dependent Claim
33 words
Cabin noise control apparatus as claimed in claim 1 characterised in that the signal processor forms part of an active noise control system which generates sound waves in anti-phase with ambient noise waves.
Claim 6
Dependent Claim
142 words
Cabin noise control apparatus for an at least two propeller or fan driven aircraft, said apparatus comprising: a plurality of transducers located inside a cabin of said aircraft; a signal processor means for receiving and analyzing signals from said plurality of transducers and for computing an estimate of a gradient of a sum of a mean square output of said transducers with respect to a phase relationship θm between at least one reference propeller or fan and at least one other propeller or fan; and a synchrophaser for varying, during flight, the phase relationship between said reference propeller or fan and said at least one other propeller or fan and in response to said signal processor means, incrementing θm an amount dependent upon the value of said gradient in order to minimize the sum of the mean square outputs of said transducers.
Claim 7
Dependent Claim
142 words
Cabin noise control apparatus for an at least two propeller or fan driven aircraft, said apparatus comprising: a plurality of transducers located inside a cabin of said aircraft; a signal processor means for receiving and analyzing signals from said plurality of transducers and for computing an estimate of a gradient of a sum of a mean square output of said transducers with respect to a phase relationship θm between at least one reference propeller or fan and at least one other propeller or fan; and a synchrophaser for varying, during flight, the phase relationship between said reference propeller or fan and said at least one other propeller or fan and in response to said signal processor means, incrementing θm an amount dependent upon the value of said gradient in order to minimize the sum of the mean square outputs of said transducers.
Claim 8
Dependent Claim
19 words
Cabin noise control apparatus as claimed in claim 5 wherein at least one of said transducers is a microphone.
Claim 9
Dependent Claim
19 words
Cabin noise control apparatus as claimed in claim 5 wherein at least one of said transducers is an accelerometer.
Claim 10
Dependent Claim
34 words
Cabin noise apparatus as claimed in claim 5 in which said signal processor comprises at least a portion of an active noise control system which generates sound waves in anti-phase with ambinent noise waves.
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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) | 1993-08-06 | 1994-02-05 | 1994-08-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-08-06 | 1998-02-05 | 1998-08-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-08-06 | 2002-02-05 | 2002-08-07 | $7700.00 | Window Closed / Lapsed |