Patent US3573400A successfully refreshed from Google Patents.
US3573400A
Expired / Lapsed
US
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Directional microphone
Assignee: AT&T Inc
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Filing: 1968-08-14
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Granted: 1971-04-06
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Expires: 1988-08-14
Abstract
Abstract A directional microphone with toroidal sensitivity characteristics which can be selectively distorted is constructed with an arrangement of acoustic tubes which sample an acoustic field at a number of separated points on an inner circle and at separated points on a concentric outer circle. The acoustic signals from the inner points are summed in a first acoustic cavity and the signals from the outer points are summed in a second cavity. The first and second cavities are separated by a foil electret or other electroacoustic transducer which produces a signal proportional to the difference in sound pressure between them. Several of the acoustic tubes may be adjusted to alter the shape of the microphone''s sensitivity pattern in the plane of maximum sensitivity and the entire acoustic system is selectively dimensioned to equalize the system''s inherent frequency response.
Inventors
- 👤 Gerhard M Sessler
- 👤 James E West
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 16:04
CPC Classifications
H; H04; H04R; H04R1/00; H04R1/20; H04R1/32; H04R1/34; H04R1/38
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
111 words
A directional transducer comprising, first and second selectively dimensioned acoustic chambers, electroacoustic transducer means for converting the acoustic signals in said acoustic chambers into electrical signals, a first plurality of exposed acoustic tubes opening into said first acoustic chamber and extending radially outward therefrom to sample a sound field at a plurality of points on a first circle exterior to said chambers, and a second plurality of exposed acoustic tubes opening into said second acoustic chamber and extending radially outward therefrom to sample a sound field at a plurality of points on a second circle exterior to said chambers, said first and said second circles being concentric and having different radii.
Claim 2
Dependent Claim
111 words
A directional transducer comprising, first and second selectively dimensioned acoustic chambers, electroacoustic transducer means for converting the acoustic signals in said acoustic chambers into electrical signals, a first plurality of exposed acoustic tubes opening into said first acoustic chamber and extending radially outward therefrom to sample a sound field at a plurality of points on a first circle exterior to said chambers, and a second plurality of exposed acoustic tubes opening into said second acoustic chamber and extending radially outward therefrom to sample a sound field at a plurality of points on a second circle exterior to said chambers, said first and said second circles being concentric and having different radii.
Claim 3
Dependent Claim
141 words
A directional electroacoustic transducer which comprises, a first selectively dimensioned acoustic chamber, a second selectively dimensioned acoustic chamber, at least one electroacoustic transducing element associated with said first and second acoustic chambers for converting the acoustic energy in said chambers into electrical signals, a first group of acoustically conductive tubes with exposed ends opening into said first acoustic chamber and extending outward from said first acoustic chamber a first selected distance to reception points on a first circle of radius r, and a second group of acoustically conductive tubes with exposed ends opening into said second acoustic chamber and extending outward from said second acoustic chamber a second selected distance to reception points on a second circle of radius R, where R is greater than r and where said first and second circles are concentric and lie in the same plane.
Claim 4
Dependent Claim
141 words
A directional electroacoustic transducer which comprises, a first selectively dimensioned acoustic chamber, a second selectively dimensioned acoustic chamber, at least one electroacoustic transducing element associated with said first and second acoustic chambers for converting the acoustic energy in said chambers into electrical signals, a first group of acoustically conductive tubes with exposed ends opening into said first acoustic chamber and extending outward from said first acoustic chamber a first selected distance to reception points on a first circle of radius r, and a second group of acoustically conductive tubes with exposed ends opening into said second acoustic chamber and extending outward from said second acoustic chamber a second selected distance to reception points on a second circle of radius R, where R is greater than r and where said first and second circles are concentric and lie in the same plane.
Claim 5
Dependent Claim
34 words
A directional electroacoustic transducer as defined in claim 2 wherein a selected number of said acoustic tubes are of variable length so as to permit adjustment of the shape of said directional sensitivity pattern.
Claim 6
Dependent Claim
52 words
A directional electroacoustic transducer as defined in claim 2 wherein said first and second selectively dimensioned acoustic chambers and said first and second groups of tubes are dimensioned such that the chamber-tube systems from a Helmholtz resonator with a resonance frequency positioned at the lower end of the frequency range of interest.
Claim 7
Dependent Claim
48 words
A directional electroacoustic transducer as defined in claim 4 wherein said first group of acoustically conductive tubes comprise four tubes orthogonally positioned with respect to a central axis and wherein said second group of acoustically conductive tubes comprise four tubes orthogonally positioned with respect to a central axis.
Claim 8
Dependent Claim
93 words
A directional transducer comprising, an enclosed cylindrical casing containing an electroacoustic transducer positioned to divide said casing into first and second selectively dimensioned acoustic cavities, means sampling the sound field exterior to said casing at a plurality of selected points in the same plane for supplying aCoustic signals to said cavities, said means including a first plurality of acoustic tubes opening into said first acoustic cavity and extending radially outward from said casing, and a second plurality of acoustic tubes opening into said second acoustic cavity and extending radially outward from said casing.
Claim 9
Dependent Claim
93 words
A directional transducer comprising, an enclosed cylindrical casing containing an electroacoustic transducer positioned to divide said casing into first and second selectively dimensioned acoustic cavities, means sampling the sound field exterior to said casing at a plurality of selected points in the same plane for supplying aCoustic signals to said cavities, said means including a first plurality of acoustic tubes opening into said first acoustic cavity and extending radially outward from said casing, and a second plurality of acoustic tubes opening into said second acoustic cavity and extending radially outward from said casing.
Claim 10
Dependent Claim
31 words
A directional microphone as defined in claim 6 wherein said first and second plurality of acoustic tubes each comprise four tubes orthogonally positioned about the central axis of said cylindrical casing.
Claim 11
Dependent Claim
182 words
A directional microphone comprising, a cylindrical casing enclosed at both ends, a circular electroacoustic transducer element coextensive with the internal cross section of said cylindrical casing and located so as to separate said cylindrical casing into two selectively dimensioned acoustic chambers, a first group of four open acoustic tubes of equal length extending radially outward from the sides of said cylindrical casing, the tubes of said first group being mated to said casing so as to open into a first of said selectively dimensioned acoustic chambers and extending outward to a plurality of selected reception points located on a first circle, a second group of four open acoustic tubes of equal length extending radially outward from the sides of said cylindrical casing, the tubes of said second group being mated to said casing so as to open into a second of said selectively dimensioned acoustic chambers and extending outward to a plurality of selected reception points located on a second circle, said second circle being concentric with said first circle and having a radius greater than the radius of said first circle.
Claim 12
Dependent Claim
182 words
A directional microphone comprising, a cylindrical casing enclosed at both ends, a circular electroacoustic transducer element coextensive with the internal cross section of said cylindrical casing and located so as to separate said cylindrical casing into two selectively dimensioned acoustic chambers, a first group of four open acoustic tubes of equal length extending radially outward from the sides of said cylindrical casing, the tubes of said first group being mated to said casing so as to open into a first of said selectively dimensioned acoustic chambers and extending outward to a plurality of selected reception points located on a first circle, a second group of four open acoustic tubes of equal length extending radially outward from the sides of said cylindrical casing, the tubes of said second group being mated to said casing so as to open into a second of said selectively dimensioned acoustic chambers and extending outward to a plurality of selected reception points located on a second circle, said second circle being concentric with said first circle and having a radius greater than the radius of said first circle.
Claim 13
Dependent Claim
134 words
A directional microphone comprising first and second selectively dimensioned acoustic chambers spaced apart by a selected distance, first and second electroacoustic transducers, said first transducer being associated with said first cavity and said second transducer being associated with said second cavity, a first plurality of equal length acoustically conductive tubes opening into said first acoustic chamber and extending outward to a plurality of reception points located on a first circle in a reception plane intermediate said first and said second chambers, a second plurality of equal length acoustically conductive tubes opening into said second acoustic chamber and extending outward to a plurality of reception points located on a second circle in said reception plane, said first and second circles being concentric, and subtractive circuit means for electrically interconnecting said first and second electroacoustic transducers.
Claim 14
Dependent Claim
134 words
A directional microphone comprising first and second selectively dimensioned acoustic chambers spaced apart by a selected distance, first and second electroacoustic transducers, said first transducer being associated with said first cavity and said second transducer being associated with said second cavity, a first plurality of equal length acoustically conductive tubes opening into said first acoustic chamber and extending outward to a plurality of reception points located on a first circle in a reception plane intermediate said first and said second chambers, a second plurality of equal length acoustically conductive tubes opening into said second acoustic chamber and extending outward to a plurality of reception points located on a second circle in said reception plane, said first and second circles being concentric, and subtractive circuit means for electrically interconnecting said first and second electroacoustic transducers.
Claim 15
Dependent Claim
66 words
A directional transducer as defined in claim 6 wherein the acoustic tubes of said first plurality of tubes and the acoustic tubes of said second plurality of tubes are of equal length and equal length and e-ual cross section, and wherein said first and second acoustic cavities are dimensioned to be of equal volume, thus to achieve for said directional transducer a substantially toroidal sensitivity pattern.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-04-05 | 1974-10-05 | 1975-04-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-05 | 1978-10-05 | 1979-04-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-05 | 1982-10-05 | 1983-04-06 | $7700.00 | Window Closed / Lapsed |