US4742548A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Unidirectional second order gradient microphone
Assignee: AT&T Inc
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Filing: 1984-12-20
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Granted: 1988-05-03
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Expires: 2004-12-20
Abstract
Abstract A second order gradient microphone with unidirectional sensitivity pattern is obtained by housing each of two commerically available first order gradient microphones centrally within a baffle. The baffles have flat surfaces, are preferably square or circular and have parallel surfaces the two baffles being parallel to each other. The rotational axes of the microphones are arranged to coincide. The output signal from one of the microphones is subtracted from the delayed signal output of the other.
Inventors
- 👤 Martin Sessler
- 👤 James E. West
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 15:37
CPC Classifications
H; H04; H04R; H04R1/00; H04R1/02; H04R1/04; H04R3/00; H04R3/005; H04R1/20; H04R1/32; H04R1/40; H04R1/406
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
144 words
A microphone arrangement for use with incident wave energy whose frequency varies from a first to a second frequency, said second frequency being substantially greater than said first frequency and the first and second frequencies respectively corresponding to a first and a second wavelength, said arrangement comprising a plurality of first order gradient microphones, each microphone having first and second sensing surfaces separated by a first acoustical path, and each microphone providing an output signal; a plurality of baffles, each baffle receiving at least one associated microphone, each baffle blocking said first acoustical path of each associated microphone and creating a second acoustical path, said second acoustical path being greater than said first acoustical path and substantially less than said second wavelength; and means for combining the output signals of said microphones to provide a second order directional response pattern for said microphone arrangement.
Claim 2
Dependent Claim
144 words
A microphone arrangement for use with incident wave energy whose frequency varies from a first to a second frequency, said second frequency being substantially greater than said first frequency and the first and second frequencies respectively corresponding to a first and a second wavelength, said arrangement comprising a plurality of first order gradient microphones, each microphone having first and second sensing surfaces separated by a first acoustical path, and each microphone providing an output signal; a plurality of baffles, each baffle receiving at least one associated microphone, each baffle blocking said first acoustical path of each associated microphone and creating a second acoustical path, said second acoustical path being greater than said first acoustical path and substantially less than said second wavelength; and means for combining the output signals of said microphones to provide a second order directional response pattern for said microphone arrangement.
Claim 3
Dependent Claim
16 words
The arrangement of claim 1 wherein said combining means adds the output signals from said microphones.
Claim 4
Dependent Claim
16 words
The arrangement of claim 1 wherein said combining means subtracts the output signals from said microphones.
Claim 5
Dependent Claim
24 words
The arrangement of claim 1 wherein said combining means includes at least one delay element which delays an associated one of said output signals.
Claim 6
Dependent Claim
17 words
The arrangement of claim 1 wherein said first and second sensing surfaces are parallel to one another.
Claim 7
Dependent Claim
19 words
The arrangement of claim 1 wherein said sensing surfaces of each microphone have a different one of two polarities.
Claim 8
Dependent Claim
20 words
The arrangement of claim 6 wherein said microphones are arranged with sensing sufaces of the same polarity facing one another.
Claim 9
Dependent Claim
19 words
The arrangement of claim 6 wherein said microphones are arranged with sensing surfaces of different polarities facing one another.
Claim 10
Dependent Claim
23 words
The arrangement of claim 1 wherein a pair of microphones is substantially parallel and separated by a distance less than said second wavelength.
Claim 11
Dependent Claim
15 words
The arrangement of claim 1 wherein each microphone is centrally disposed within an associated baffle.
Claim 12
Dependent Claim
27 words
The arrangement of claim 1 further including at least one additional baffle connected to said microphones, each additional baffle being greater in size than said second wavelength.
Claim 13
Independent Claim
127 words
A method of producing a directional sensitivity pattern for a microphone arrangement for use with incident wave energy whose frequency varies from a first to a second frequency, said second frequency being substantially greater than said first frequency and the first and second frequencies respectively corresponding to first and second wavelengths, said method comprising the steps of perforating a recess through each baffle in a pair, placing a bidirectional first order microphone having first and second sensing surfaces separated by a first acoustical path into each recess, the placement of each microphone replacing said first acoustical path with a second acoustical path, said second acoustical path being substantially less than said second wavelength, each microphone providing an output signal, and combining the output signals of each microphone.
Claim 14
Independent Claim
127 words
A method of producing a directional sensitivity pattern for a microphone arrangement for use with incident wave energy whose frequency varies from a first to a second frequency, said second frequency being substantially greater than said first frequency and the first and second frequencies respectively corresponding to first and second wavelengths, said method comprising the steps of perforating a recess through each baffle in a pair, placing a bidirectional first order microphone having first and second sensing surfaces separated by a first acoustical path into each recess, the placement of each microphone replacing said first acoustical path with a second acoustical path, said second acoustical path being substantially less than said second wavelength, each microphone providing an output signal, and combining the output signals of each microphone.
Claim 15
Dependent Claim
30 words
The method of claim 12 further comprising the step of introducing a delay into the output of at least one of said microphones prior to combining the microphone output signals.
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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) | 1991-05-03 | 1991-11-02 | 1992-05-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-03 | 1995-11-02 | 1996-05-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-03 | 1999-11-02 | 2000-05-03 | $7700.00 | Window Closed / Lapsed |