SU93157A1 - Line Integral Reverberometer - Google Patents

Description

The subject of the invention is a linear-integral reverberometer for the study of room acoustics.

The proposed linear-integral reverberometer differs from the already known instruments of similar purpose used by the linear detector simultaneously with the linear integrator device. Such an instrument design makes it possible to simplify and speed up the process of measuring the reverberation time of the investigated elements.

FIG. 1 shows the electrical circuit of the integrator based on the electric ballistic principle; pas figs. 2 is an electrical circuit of an integrated device with a choke; pas figs. 3 is a skeleton diagram of an apparatus for measuring the reverberation time and in FIG. 4 is a schematic diagram of a linear-integral reverberometer using a high-capacity capacitor as an inertial element.

To determine the reverberation time of a room with the required accuracy, the measurements must satisfy two basic requirements.

First, in each room it is necessary to measure

in such a number of points that, 10 possible statistical averaging.

. Secondly, the measurement method should be such that as a result of arithmetic averaging of the results of many measurements made at different points in the room, the total result of deviations of individual processes of attenuation from the average law is statistically compensated.

To satisfy the first requirement, the method should provide the required measurement speed.

The second can be recalled: not if the readout (R) of the reverberometer, when measured at all individual points, will correspond to the CONDITION:

FI: / {ip (t} dt,

where P (1) is a function that determines the dependence of the sound pressure at a given point of a room on time in the process of reverberation damping, and K is the constant of the reverberometer.

With these two requirements, the existing methods are not adequately satisfied, and as a result, the measurements of the reverberation time are complicated and slow down. The proposed linear-integral reverberometer eliminates this drawback and allows us to simplify and speed up the process of measuring the reverberation time by using an electrically inertial system based on the electrobalance principle. An electrically inertial system can be practically realized either with the help of a large-capacity electric capacitor, or with the help of throttles with a large inductance. The electrical diagram of the integrating device based on the electrobearist principle using the condisator is shown in the FNG. 1. The magnitude of the current / a flowing through the sonic resistance Rz under the influence of an impulse of an electromotive force E, which varies exponentially in time, is determined by the differential equation .. uhA i, c,. / e, /, c, The solution of equation (2) has the form //, -I / h (i) IR - / R, R, C, V / ,, The maximum force ka ii is defined by the expression 1 / s, R, C, /, + R. Since the attenuation coefficient is related to the time of the standard reverberation T by the ratio -, (5) subject to the fact that pr and i s is 1, i.e. condition 6.9 K, + R , R, R, C, the maximum magnitude of the current "2 will be determined by the expression: E T 6.9;, ° / C, From the expression (8) it can be seen that, measuring 1-pgl .: at a certain value fo, It is possible to determine the time of the standard reverberation T. If between the sound pressure.m.P (i, acting on the microphone and the electric There is a linear relationship to the thromotive force at the input of the integrating device, then the maximum current value ii, and therefore the reverberometer readings will correspond to condition (1). Operate for exponential attenuation of sound: О "/ С / С," Г Thus, if the inertia of the integrating device is sufficiently large, which is determined by the fulfillment of condition (7), the readings of the reverberometer will be proportional to the area bounded by the attenuation curve and the coordinate axes of time and sound pressure. It can be shown that this will be true for those cases where the sound attenuation curve has partial deviations from the exponential law. In this case, the readings of the reverberometer will correspond to the reverberation time of the ideal decay process, i.e., an exponential process and equivalent to the measured integral of the sound pressure over time. The electrically inertial system can also be obtained using drossel. The electrical circuit of the integrator with the choke is shown in FIG. 2. The current I flowing through the choke under the influence of an exponential impulse of an electromotive force is determined by a differential equation; and A Yao -f --- dt /. The solution to this equation is i (t Maximum force k i is determined by the expression MlL-i K the maximum magnitude of the current is defined by the expression T This shows that I integrate; all throttle-type device, under the conditions (13), also provides determine the reverberation time by measuring the integral reverb effect according to condition (I). Fig. 3 shows the skeleton diagram of the inclusion of all the equipment needed to measure the reverberation time. nerator / howling tone, loudspeaker 2, microphone 3. microphone amplifier 4, detector 5, switching device 6 and integrating its device 7. The switching device, which should ensure the inclusion of the integrated 1, its devices simultaneously with the beginning of the reversal process, can be practically implemented with the help of an electromagnetic relay. A schematic diagram of a linear-integral reverberometer using a large capacitor as the inertial element is shown in FIG. 4. Measurement of the reverberation time using such a reverberometer is as follows. When the button 8 is open, the contact springs 9 of the relay 10 occupy the position shown in the diagram. In this case, the capacitor Ci of the integrating device is closed} and short, the circuit L of the loudspeaker and the room is filled with sound energy. The sound vibrations affect the microphone and, accordingly, the microphone currents are detected with the aid of a lamp 12 and are applied to an integrating device. The initial voltage at the input of the integrator, which corresponds to the steady state sound level in the room, is monitored by the readings of the galvanometer 13 and is set to a certain value by adjusting, amplifying the microphone silytel 4 or the voltage at the output of the generator / howl tone that feeds loudspeaker 2. When you press 8 relay W triggers and the ohvrememeino breaks the loudspeaker chain and the circuit shorting the capacitor C. As a result of this, a current flows through the resistance, the amplitude of which measured by galvanometer 14, is directly proportional to the reverberation time. The subject of the invention is a line-integral reverberometer, which is designed so that, in order to quickly obtain indications suitable for arithmetic averaging, it simultaneously uses a linear detector and a linear ballistic device, for example, galvanometer with integrating RC or RL circuit. 0-1-WVVWV

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