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-

••/•o

I

25• ' N•,,,,. • ø '

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: 130.209.6.50 On: Sun, 21 Dec 2014 21:40:05