Telephonic communications – Substation or terminal circuitry – For loudspeaking terminal
Patent
1989-12-22
1992-06-09
Dwyer, James L.
Telephonic communications
Substation or terminal circuitry
For loudspeaking terminal
379420, 379390, 379432, 381 92, 381 83, H04M 120, H04R 132
Patent
active
051214261
ABSTRACT:
A loudspeaking telephone station (speakerphone) includes a loudspeaker and one or more microphones within the same housing. The microphones are directional, each having a polar response characteristic that includes a major lobe, one or more side lobes, and nulls between pairs of lobes. The loudspeaker is positioned in the null of the polar response characteristic that resides between the major lobe and an adjacent side lobe. The microphone apparatus is positioned so that its major lobe is aimed in a direction that is generally perpendicular to the direction that the loudspeaker is aimed. Means are provided for increasing the distance between input sound ports of a first-order-gradient (FOG) microphone and thereby improving its sensitivity. A pair of such improved FOG microphones are used in assembling a second-order-gradient microphone. Full duplex operation is achieved when a pair of echo cancelers are added to further reduce the coupling between the transmit and receive directions of the speakerphone.
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Knowles Electronics, Inc.--Technical Bulletin TB-21 "EB Directional Hearing Aid Microphone Application Notes".
Baumhauer, Jr. John C.
McAteer Jeffrey P.
Wittman Brian A.
AT&T Bell Laboratories
Dwyer James L.
Morra Michael A.
Shehata M.
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