SU29612A1 - Method for measuring sound reverberation - Google Patents

Description

A method for measuring the sound reverberation is proposed.

Its essence is that the reverberation time is determined by the ratio of the amount of sound remaining in the room after turning off the sound source, and measured by the indications of a ballistic galvanometer that is switched on in the detector circuit simultaneously with the sound source turned off. in the same circuit under the action of the sound source.

The drawing shows schematically an installation for carrying out the proposed method.

With sound source 7, a room is filled with sound vibrations, which after some time are mixed with sound vibrations due to the echo of the room. These acoustic signals, perceived by the D1 microphone 2, amplified in the cathode amplifier 3, are detected by the detector 4, the current of which is recorded by an ordinary galvanometer 5.

After the installation of the sound vibrational mode in the room, which is judged by the established maximum

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readings of galvanometer 5, proceed to measurement.

Record the indication of the above-mentioned galvanometer and turn off the sound source / with simultaneous switching of the detector 4. With the terminals of the galvanometer to the clamp of the ballistic galvanometer 6.

The constant current J in the anode circuit of the detector lamp of the sensing device can be considered proportional to the strength of the sound in front of the microphone, so that the ratio of sound values can be replaced by the ratio of the corresponding electrical ones.

The decrease of the current J during the reverberation of the sound in the room will occur according to a known law:

 Yc - current with a valid sound source,

k is constant for a given room.

Ai

(kA is the absorption of the room, f is the speed of sound, w is the volume).

The integral of / over time will characterize the amount of sound remaining in the room after turning off the sound source.

Denote this integral by /, then:

 - -.

oo

From where

k- ° K-JIf k is known, one can find out the reverberation time t- (during the reverberation time, usually a time is assumed, during which the primary amplitude is reduced by 10 times).

Indeed:

If given:

ki.

1-6

/.And10 In 1 (G

or, substitute the value of k:

t, -4J.

To determine / use, as was said above, an ordinary galvanometer incorporated into the detector circuit.

To determine the same / serves as a ballistic galvanometer, turned on the place of the ordinary simultaneously with the shutdown of the sound source. Since the reverberation time can be quite long (up to 8 seconds), the intrinsic period of the ballistic galvanometer must be, in order to obtain greater accuracy of measurement, in the order of 3-5 minutes.

It should be noted that according to neg 1 jjdt

which acoustics size

sufficiently characterizes the acoustic merit of the room, provided that the sound source is constant (see, for example, The Bell System, Technical journal April. 1930).

The subject matter of the invention.

The method of measuring the reverberation of sound, characterized in that the reverberation time is determined by the ratio of the amount of sound that is in the room after turning off the sound source and measured by the indications of a ballistic galvanometer 5 included in the detector circuit 4, simultaneously with the sound source turned off using a galvanometer 6 current in the same circuit under the action of the sound source.