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STEERABLE STEREO VARIABLE DIRECTIONAL PATTERN MICROPHONE REQUIRES ONLY TWO CHANNELS

IP.com Disclosure Number: IPCOM000005469D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2001-Oct-10
Document File: 2 page(s) / 101K

Publishing Venue

Motorola

Related People

Richard E. Werner: AUTHOR

Abstract

The steerable stereo, variable dlrectlonal pattern, mlcrophone system provided by two coincident or- thoganally disposed cosine pattern microphones and one coincident omnidirectional microphone (or the various combinations of limacon family microphone which may be matrixed to provide the equivalent) re- quires three transmission or recording channels for full exploitation.

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@ MOTOR0L.A Technical Developments Volume 2 January 1982

STEERABLE STEREO VARIABLE DIRECTIONAL PATTERN MICROPHONE REQUIRES ONLY TWO CHANNELS

By Richard E. Werner

ABSTRACT

   The steerable stereo, variable dlrectlonal pattern, mlcrophone system provided by two coincident or- thoganally disposed cosine pattern microphones and one coincident omnidirectional microphone (or the various combinations of limacon family microphone which may be matrixed to provide the equivalent) re- quires three transmission or recording channels for full exploitation.

   A method is described by which much of the effectiveness of the three-channel system is retained when transmission or recording circumstances permit only two-channel operation. The listener retains the means to reject undesired sounds and selects desired sounds by control of the directivity of the microphones and the direction in which they are pointed, and by his own stereophonic discrimination.

THREE-TO-TWO (Figure 1)

   The orthogdnal cosine pattern mlcrophone signals are matrixed via constant 90' phase different net- works to obtain a toroidal directional pattern. The sensitivity in the plane of the torus is uniform: but the phase of the electrical signal is correlated with the angular direction to the sound source. This signal Oc- cupies one channel and the omnidirectional microphone signal occupies the second channel.

RECEPTION (Figure 2)

   Subsequent to reception (or playback), one of the signals is passed through a controllable phase- shlft circuit so that when summed with the other channel, the signals will be additive for sounds from one direction and subtractive for the opposite direction. Depending upon mixing ratios, various directional patterns are achievable with the usual limacon family being observed in a plane perpendicular to the plane of the torus whereas a broader pattern Is achieved in the plane of the torus. Th...