SU1233033A1 - Method of measuring sound pressure - Google Patents

Abstract

The invention relates to acoustic measurements in liquid and gaseous media and can be used to measure the pressure generated by a low frequency acoustic source. The aim of the invention is to expand the technological capabilities of the measurement by measuring the absolute pressure. According to the method of measuring sound pressure in the range of low-frequency elastic waves, whose pressure is measured, acoustic transducers are installed. First, a high-frequency elastic wave is excited at an angle of 0 to the direction of propagation of the sound wave. A phase-modulated high-frequency wave is adopted by the transducer due to non-linear interaction with the low-frequency wave. The maximum phase shift of the LF is measured between signals on the transducers. Then, a high-frequency wave is excited in the opposite direction, and the maximum phase shift Δf between signals on the transducers is measured. The formula for calculating the low frequency pressure is given. 1 il. from € ate N3 with so about so with so

Description

The invention relates to acoustic measurements in liquid and gaseous-gas environments and can be used to measure the pressure produced by a low-frequency acoustic source.

The aim of the invention is to expand the technological capabilities of the measurement by providing the possibility of measuring the absolute sound pressure.

The drawing shows an installation diagram for implementing a method for measuring sound pressure.

The installation contains reversible acoustic transducers 1 and 2 for emit- ting a high-frequency pump wave, an acoustic source 3 of a low-frequency signal, a generator of 4 high-frequency waves, a synchronous switch 5 and a series-connected amplifier 6, a phase detector 7, a low-frequency amplifier 8 and an indicator 9.

The method of measuring sound pressure is carried out as follows.

In the area of propagation of acoustic waves generated by acoustic source 3, reversible acoustic transducers 1 and 2 are installed. When the signal from the 4 high-frequency wave generator is applied, acoustic transducer 1 emits high-frequency elastic waves whose frequencies are at least 10 times higher than the frequency of sound waves. In the case of nonlinear interaction of sound waves with high-frequency elastic waves, the modulus of the phase of the second oscillation first occurs. Phase modulation of a high-frequency wave is caused by a change in the velocity of propagation of its profile points in the field of a low-frequency wave, which depends on the magnitude of the alternating density pressure and the velocity of displacement of particles of the medium. High frequency acoustic transducers 1 and. 2 is set at a distance not greater than two wavelengths of the low frequency signal, and the direction of propagation of high frequency elastic waves is chosen at an angle of 0 to the direction of propagation of low frequency elastic waves. Acoustic transducer 2 receive a high-frequency phase-modulated signal. The magnitude of the maximum value of the time-varying F d shift of the QF between the signal

with acoustic transducers 1 and 2, for which the phase shift selected in the phase detector 7 is amplified and recorded on the indicator 9. Then, the input of the acoustic transducer 2 is connected with the key 5 to the output of the high-frequency generator and an electrical signal is sent to it. At the same time, high-frequency elastic waves are excited in the opposite direction, which are again modulated by low-frequency elastic waves. In this case, the geometrical conditions of propagation and interaction of the waves are identical; they change only by 180 the angle at which the elastic waves intersect. Acoustic transducer 1 receives a high-frequency signal modulated in phase by measured low-frequency pressure, for which the output of transducer 1 is switched to input of amplifier 6 using key 5. Measure the value of the maximum value of the phase shift Ц between signals from acoustic transducers 2 and 1. The measured low-frequency pressure is determined by the formula

3

Optch, - m) j,

p.

.

2L jcos9

where p, c is the density and speed of sound in an unperturbed medium;

L is the distance between the points of excitation and reception; - high frequency

elastic waves; n, m - coefficients;

- the length of the low-frequency

elastic wave; n m 1 when L Oh, 2.

45

n 4 (1 - cosQ)

sin (GH 1 - so89);

50

m

(1 + COS0)

- with L - 2 A.

 + convocations)

55

 The method of measuring low frequency pressure allows direct measurement of the absolute pressure generated by an acoustic source, since it eliminates. the need for prior

measurements of the nonlinearity parameter of the medium or comparison with reference receivers.

Claims (1)

Invention Formula J The method of measuring sound pressure, which implies high-frequency elastic waves, which propagate at an angle of 9 to the direction of propagation of sound waves, receive high-frequency elastic waves at another point, measure the time shift between; 1, the high-frequency elastic waves at the points of their excitation and reception and phase shift determine the pressure, characterized in that, in order to expand the technological capabilities rhenium due to measuring absolute pressure, fixed maximum phase shift L V, then excite high-frequency elastic waves in the opposite direction, the maximum measured value of the phase shift ,, dm Editor R. Tsitsika Compiled by G.Fyodorov Tehred O. GortvayorGorReshetnik. 272/45 Circulation 778 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., d. A / 5 Production and printing company, Uzhgorod, st. Project, 4 I 2330: 334. and sonic darle) P1e 1.- determined by the formula R 2L.uu cosQ - (lh &,) where p, Cd - density and speed of sound in the undisturbed medium, respectively; L is the distance between the points of excitation and reception of high-frequency elastic waves; jj is the frequency of high-frequency elastic waves; k is the length of the sound wave; n, nn are the coefficients of V -, --- th 1 for L 0.2 and 20 1TL 1 cos 9) h TTL G b, 1 (l-cos9) j HL ,, (cos Q 1 rr Sih Til at L Q l . (1 cos 91