Electret transducer with variable electret foil thickness

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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 Snsitivity 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: 84.88.136.149 On: Thu, 18 Dec 2014 10:06:32