US4424419A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electret microphone shield
Assignee: Nortel Networks Ltd
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Filing: 1981-10-19
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Granted: 1984-01-03
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Expires: 2001-10-19
Abstract
Abstract An electret microphone has a metal shield around it in order to guard against electromagnetic interference. Acoustic waves reach the electret element through a passage in the shield. The electret response is undesirably affected by an electric field produced by body capacitance when the microphone is brought close to a user's mouth. To overcome this effect, the microphone has a conductive film, transparent to acoustic waves, positioned between the passage and the electret element, the film contacting a grounded part of the casing. The conductive film can form an integral part of a microphone moisture barrier.
Inventors
- 👤 Guy J. Chaput
- 👤 Edward M. Sich
- 👤 Beverley W. T. Gumb
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 23:24
CPC Classifications
H; H04; H04R; H04R19/00; H04R19/01
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
69 words
In an electret microphone comprising a casing and an electret element within the casing for producing an electrical signal corresponding to acoustic vibration passing into the casing through a passage therein, the improvement comprising a conducting film blocking the passage, the conducting film transparent to said acoustic vibration and impermeable to moisture, the film electrically contacting a fixed potential body whereby to fix the potential of the conducting film.
Claim 2
Dependent Claim
69 words
In an electret microphone comprising a casing and an electret element within the casing for producing an electrical signal corresponding to acoustic vibration passing into the casing through a passage therein, the improvement comprising a conducting film blocking the passage, the conducting film transparent to said acoustic vibration and impermeable to moisture, the film electrically contacting a fixed potential body whereby to fix the potential of the conducting film.
Claim 3
Dependent Claim
21 words
An electret microphone as claimed in claim 1, in which the conducting film comprises a conducting layer deposited on a substrate.
Claim 4
Dependent Claim
18 words
An electret microphone as claimed in claim 2, in which the substrate is a film of flexible plastics.
Claim 5
Dependent Claim
23 words
An electret microphone as claimed in claim 3, in which the combination of the plastic substrate and the deposited conducting layer is moisture-impermeable.
Claim 6
Dependent Claim
32 words
An Electret microphone as claimed in claim 4, further comprising a sealing member pressing the combination of said substrate and the conducting layer into engagement with an inside surface of the casing.
Claim 7
Dependent Claim
28 words
An electret microphone as claimed in claim 1, in which the casing is conducting and is grounded, said conducting film electrically contacting an inner surface of the casing.
Claim 8
Dependent Claim
21 words
An electret microphone as claimed in claim 6, in which both the conducting film and the casing are made of aluminum.
Claim 9
Dependent Claim
20 words
An electret microphone as claimed in claim 1, in which the conducting film is composed of a conductor loaded plastic.
Claim 10
Dependent Claim
14 words
An electret microphone as claimed in claim 8, in which the conductor is carbon.
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) | 1987-01-02 | 1987-07-04 | 1988-01-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-01-02 | 1991-07-04 | 1992-01-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-01-02 | 1995-07-04 | 1996-01-03 | $7700.00 | Window Closed / Lapsed |