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4,429,189
43.88.Hz ELECTRET TRANSDUCER WITH A
SELECTIVELY METALIZED BACKPLATE
David A. Berkley, I!ene J. Busch-Vishniac, Robert L. Wallace, Jr., and James E. West, assignors to Bell Telephone Laboratories, In- corporated
31 January 1984 (Class 179/111 E); filed 20 November 1981
This is one of five co-filed and co-issued patents having to do with various implementations of a directional, electret transducer line array pre- viously disclosed by R. L. Wallace. A vertical array of small microphone elements can achieve a desirable lighthouse-beam pattern in the speech range, making it ideal for conference table voice pickup. Indeed, a commer-
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cial application of the patent is found in AT&T's "Quorum" teleconferenc- ing system. Instead of using individual microphone elements, this new ver- sion proposes a single strip electret 10 superimposed on a selectively metalized backplate. The patent includes a great deal of interesting informa- tion about electret transducers in general as well as the present trans- ducer.--GLA
4,429,190
43.88.Hz CONTINUOUS STRIP ELECTRET
TRANSDUCER ARRAY
Christopher D. G. Stockbridge, assignor to Bell Telephone Laborato- ries, Incorporated
31 January 1984 (Class 179/111 E); filed 20 November 1981
Number 2 in a series of five patents describes a continuous electrot strip superimposed over a metallic backplate having a plurality of large areas connected by thin strips. This variant simulates the original discrete trans- ducer array rather than a continuous line cquivalcnt.--GLA
4,429,191
43.88.Hz ELECTRET TRANSDUCER WITH VARIABLY
CHARGED ELECTRET FOIL
Ilene J. Busch-Vishniac, Robert L. Wallace, Jr., and James E. West, assignors to Bell Teleph6ne Laboratories, Incorporated
31 January 1984 (Class 179/111 E); filed 20 November 1981
Number 3 in this group of five patents describes several p{actical ways to achieve the effect of an electret strip line source in which the electrostatic charge varies according to some desired relationship.•GLA
4,429,192
43.88.Hz ELECTRET TRANSDUCER WITH VARIABLE
ELECTRET FOIL THICKNESS
I!ene J. Busch-Vishniac, Robert L. Wallace, Jr., and James E. West, assignors to Bell Telephone Laboratories, Incorporated
31 January 1984 (Class .179/111 E); filed 20 November 1981
Still another way to control the S•nsitivity of an electret strip trans- ducer is to vary the effective air gap betweeit.the electret foil and the back- plate.•GLA
4,429,193
43.88.Hz ELECTRET TRANSDUCER WITH VARIABLE
EFFECTIVE AIR GAP
I!ene J. Busch-Vishniac, Robert L. Wallace, Jr., and James E. West, assignors to Bell Telephone Laboratories, Incorporated
31 January 1984 (Class 179/111 E); filed 20 November 1981
The last patept in this group of five ties things up by describing still another method for varying the effective air gap of an electret strip trans- ducer. In this case, a plurality of holes is drilled in the backplate.•GLA
4,560,840
43.88.Si DIGITAL HANDSFREE TELEPHONE
Bjorn N. Hansen, assignor to International Standard Electric Corpo- ration
24 December 1985 (Class 179/81 B); filed in the United Kingdom 1 March 1983
The speakerphone circuit described here uses microprocessor control by which the microphone signal, background room noise, and the telephone channel speech signal are sampled to determine their amplitudes. Signal levels are compared to preset thresholds, and lookup tables of attenuation controls are used to govern the gain settings for the speech pathways so as to prevent acoustical feedback and to perform voice-controlled transmit/re- ceive switching.•DLR
467 J. Acaust. Sac. Am. 84(1), July 1988; 0001-4966/88/070467-01500.80; ¸ 1988 Acaust. Sac. Am.; Patent Reviews 467
Redistribution subject to ASA license or copyright; see http://acousticalsociety.org/content/terms. Download to IP: 132.174.255.116 On: Thu, 27 Nov 2014 04:55:15
