GB435980A - Improvements in or relating to the stereophonic reproduction of sound - Google Patents

Abstract

435,980. Reproducing music &c. ELECTRICAL RESEARCH PRODUCTS, Inc., 195, Broadway, New York, U.S.A.-(Assignees of Friebus, R. T. ; 15, Marion Road, Montclair, New Jersey, U.S.A.) April 17, 1935, No. 11848. Convention date, April 26, 1934. [Class 40 (iv)] In a sound-reproducing system employing two or more spaced microphones feeding spaced loud-speakers over separate channels, the apparent lateral position of the sound source is dependent mainly on the relative strengths of the direct waves received by the microphones, while the apparent " fore and aft " position is dependent mainly on the relative strengths of the direct and reflected waves received by the microphone nearest to the source. In order to simulate any desired positional effects, such as movement of the source, each channel is connected to the microphones so as to receive currents corresponding to both direct and reflected sound energy in variable proportions. Fig. 1 shows two channels 13, 14 feeding loud-speakers 15, 16 and each receiving currents from microphones 10, 11 through independently variable volume control devices 22, 23, 26, 27. It is explained how the volume controls may be adjusted to simulate movements of a single performer and of an orchestra on the dummy stage 12. One or both of the microphones may be moved while the controls are being manipulated. Fig. 4 shows three channels 51-53 feeding spaced loud-speakers 66-68 and each receiving currents from a " close-up " microphone 60 and a " distant " microphone 63 through separate volume controls 54, 55. In addition, auxiliary " off-stage " loudspeakers 69, 70 may be connected to the outer channels 51, 53 in parallel with the loudspeakers 66, 68, each having a separate volume control 71-74. This arrangement is useful to simulate the passage of a band across the dummy stage. In Fig. 7, each of the two channels 90, 91 receive currents from a " closeup " microphone 60 and a "distant" microphone 63 as in Fig. 4 and also a proportion of the currents in the other channel through a volume control 92 or 93. Each channel feeds two loud-speakers 66, 94 located one above the other through volume controls 72, 96. The arrangements may be adapted for recording and subsequent reproduction, a separate record or sound track being made for each channel.