The Digital Reverberation Time Meter

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  • Date Hikaru
    Technical Research Laboratory, Japan Broardcasting Corporation

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  • ディジタル残響計
  • ディジタル ザンキョウケイ

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Abstract

A new electronic digital reverberation time meter was devised, which enables to indicate automotically the average of reveberation times (Tm) observed in N repeated times. The composition is as follows: The first system is a sound pulse generator. Repetition period of a sound pulse is adjustable to be any one of 0. 5, 1, 2 and 3 seconds. Pulse duration is about a half of them. The second system is composed of level discriminating circuit and gating circuit, which makes counting pulses pass while reverberation falls through an appointed level range (adB), actually 10, 20 or 30 dB. The third system is a circuit which stops the counting when number of observations reaches N. The fourth system is a pulse counting circuit of decimal type. Frequency of counting pulse is selected to the value equal to 60/a・1/N・10^n p. p. s. , so that the counting tubes indicate Tm×10^n directly. In general it is necessary to observe a number of reverberation curves in order to obtain the reverberation time of a room with desired accuracy, so the new device can eliminate much of time and efforts comparing with a high speed level recorder which is widely used.

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