GB1001518A - Artificial reverberation apparatus - Google Patents

Abstract

1,001,518. Reverberation systems; stereophonic systems. WESTERN ELECTRIC CO. Inc. Sept. 14, 1961 [Sept. 29, 1960], No. 33046/61. Heading H4R. Artificial reverberation apparatus comprises, connected between a signal input for electrical signals representative of sound and a signal output, at least one all-pass network comprising a path including means 31 (Fig. 3a) for producing fractional gain, delay means 33 connected parallel to the means 31 and means 34 producing fractional gain and connected to feedback signals from the output to the input of the delay means 33. Output signals are obtained having substantially no attenuation of any frequency relative to other frequencies in the bandwidth of the input signals. A portion of an input signal is applied to an amplifier 31 of gain (- g) less than unity while the remainder is passed by an addition network 35 to a delay device 33. A portion of the output from the delay device is applied through an amplifier of gain (1 - g<SP>2</SP>) to an addition network 32 where it is added to the signal from amplifier 31. The remainder is fed back through amplifier 34 of gain (+ g) to be passed through the delay device 33 again. The gain g is 0À7 and the gain of the apparatus as a whole is unity for all frequencies. Several such apparatuses may be connected in tandem (Fig. 4, not shown) in which case the delays of the delay devices are such that the delay of one of them is equal to the overall reverberation time required and the delays of the others form a geometrically diminishing sequence. One or more such apparatuses 55 (Fig. 5) may be connected with " comb filter networks " 51, 52, 53 each consisting of a delay device 21 (Fig. 2a) and a feedback loop 22 of gain (+ g) less than unity. Quasi-stereophonic apparatus.-Two output signals are derived from a single input signal by two artificial reverberation apparatuses each comprising a delay device 61 or 61<SP>1</SP> (Fig. 6) and a feedback loop 62 or 62<SP>1</SP>. An undelayed path 63 or 63<SP>1</SP> is provided in each apparatus. For the apparatus with positive feedback loop 62 a difference output signal is obtained in subtracter 66 and for the apparatus with negative feedback loop 62<SP>1</SP> a sum output is obtained at addition network 67.