SU1021954A1 - Method of absolute determination of acoustic wave pressure amplitude - Google Patents

Abstract

METHOD OF ABSOLUTE DEFINITION. The amplitude of the PRESSURE of the ACOUSTIC JULNA, which consists in the fact that a plane acoustic wave is excited, is recorded using an informative parameter transducer at the frequency of the excited wave at two points of the medium at a fixed distance B. from the other in the direction of wave propagation and the measured parameters determine the amplitude of the pressure of the excited acoustic wave, characterized in that, in order to expand the range of the measured pressure amplitudes and improve the accuracy, as an informative th parameter selected amplitude of the received transducer signals, their measured at the doubled frequency 25 and amplitude of the acoustic wave pressure is calculated by the formula CM iPa-t | Pii-P afPn P - 1 ftSCJ l) E where p - density of the medium; C is the speed of sound in the medium, Y is the nonlinearity parameter of the medium / f Py, mRu, are the measured values of the amplitudes of the signals at the frequency (W 1) and 2. (

Description

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4; ai The invention relates to acoustic and acoustic measurements and can be used for absolute calibration of acoustic transducers. A known method for the absolute determination of the amplitudes of the pressure of an acoustic wave, which consists in measuring the radiation pressure using a radiometer made, for example, in the form of a light disk, pin or cone, the dimensions of which are much larger than the length of the sound wave, and based on these measurements determine the amplitude of wave i. . The disadvantage of the method is its low noise immunity, since the radiameter readings are influenced by acoustic currents, conventional currents and other currents. In addition, the method cannot be used to measure amplitudes in a pulsed emission mode. A technical approach and an achievable result is a method for absolute determination of the amplitude of the pressure of an acoustic wave, consisting in that a plane acoustic wave is excited in a medium, and an informative parameter is recorded at frequency I of the excited wave at two points of the medium, found 1x at a fixed distance 1 from one another in the direction of the propagation of the wave, and according to the measured parameters distribution of the amplitude of the pressure of the excited acoustic wave. As an informative filter, choose the oscillation phase and the magnitude of the amplitude of oscillations of the phase difference at two reception points arising due to acoustic modulation of the wave propagation time due to excitation of low-amplitude low-plane plane waves of large amplitude, the amplitude P of the pressure t2 is determined. The disadvantage of this method is relatively narrow range of pressure amplitudes measured. This is caused, first of all, by the ambiguity of reference of the deviation phase, namely, there is such a value of pressure power P | where the phase oscillation rate is the same at the amplitudes of the acoustic wave pressure P, P + P, P + 2P, etc., i.e. unambiguous determination of the pressure amplitude is possible only in the range not exceeding Pn. In addition, the results change. , -. . Rhenium is affected by an additional phase shift due to acoustic wind. The purpose of the invention is to expand the range of measured pressure amplitudes and to increase the accuracy. This goal is achieved by the method of absolute v determining the amplitude of the pressure of an acoustic wave, which consists in the fact that a plane acoustic wave is excited in a medium, and an informative parameter is recorded at a frequency of the excited wave at a fixed distance between the waves of the excited wave } one from in the direction of the wave propagation, and the measured amplitude of the pressure of the excited acoustic wave is determined from the measured parameters; the amplitudes n yn received signals transducer measured at the doubled frequency of 2 and the amplitude of the acoustic wave pressure P is calculated by the formula 1R11) R.1-Rag1% 1) p is the density of the medium; with the speed of sound in the environment; -y-parameter non-linearity of the medium / Р and RP-measured values of the amplitudes of the signals at the frequency (m-1) and 2 (and-2) at the first and second receiving points. The drawing shows a block diagram of the device dp implementation of the method. The device contains electroacoustic-connected harmonic oscillator 1, radiating 2 and wideband receiving 3 transducers placed in 4, acoustic parameters f, known for which, wideband amplifier 5 and spectrum analyzer 6. The essence of the method is as follows. in the medium, a plane acoustic wave is excited, for example, by means of a piezo-transducer. Due to the nonlinearity of the medium in the latter, an acoustic wave is excited at the double frequency, the amplitude of which depends on the amplitude P of the excited wave frequency and the distance from the radiator. Then, a broadband acoustic receiver receives the acoustic signal at two points at distances 1 and 1 from the center of the radiating transducer, whereby the amplitude p of signals at frequency E and frequency 2f is measured, for example. , The true values of the amplitudes U at the frequency and at the frequency 2 and the measured values of the signals Py, at each point I w z zash: ratios P 10 MPaG-Rao (e, -), (1) where tC is the unknown path conversion factor. Since at each reception point at frequency 2, not only the pressure amplitude due to the non-linearity of the medium is recorded, but also the pressure amplitude Pc, caused by the non-linear non-linearity of the trajectory, (always, the presence of a signal at 2f, KOTOptaR, is always present in (The “receiving signal amplitude in TO4Kieix receiving signal amplitude at frequency 2 {equal to Р CE V Hiliilb ОЧр - ioc; 1 such as for a flat wave TüSe.) Р, (ea) -R. P; picking attentive relations (2) and (3), the true value of the amplitude P of the pressure of the acoustic wave mon determine if the radiated wave is not flat, if the radiated wave is not flat, the measurement of the south pressure can be determined from the relation failPn-PteiPn) 1Cf (4.1 where A is the parameter, xfact izunci wave type, and A 2 for a plane wave, A a spherical wave No. 1 and A 2V R / RO for a center of a liidric wave, R is (C + 1d) / 2, the Re is the radius of the irradiating radiation generator. The method with the device is performed as follows l, With the help of a generator of electrical signals 1 and a transducer 2, for example, of a piezoceramic one, i.e. 4 excites the acoustic frequency wave. By moving the phyme piezoelectric generator 3 in the acoustic emission of the acoustic wave, the signal is received by an acoustic signal, amplified by a wideband amplifier that ensures equal amplification of the signals at frequencies {- to 2, and using the spectator channel b) you divide and measure amplitudes (signals at frequency i and 2 {. The amplitudes are substituted into formula (1) to calculate the true pressure of the acoustic wave. It should be noted that the operating ability of the method does not depend on the configuration of the converter 3, since avisit l (m1 path conversion coefficient, knowledge of which is not necessary. When implementing the method, it is necessary to provide a pure traveling wave mode, since if there is even a small amplitude of the wave, the amplitude of the received signal can vary as the transducer moves 3 and ffmula (1) is not fair. Therefore, the manufacture of the converter 3 in the form of a hollow sphere or a tubular cylinder can be its dimensions | in principle, any compared to the wavelength, and in the manufacture of converter 3, the plate should either be made smaller in size than the length of the wave1, so that it doesn’t cost a lot of waves, or work in long immersion mode (lasting about 10 periods of high frequency fill) and measurements carried out on the first transmitted pulse, excluding repeatedly reflected, for example, by time gating. The method practically does not contain restrictions on the range of measured values. The maximum pressure amplitude of the acoustic wave, which can be measured, is determined by the contraction of And in the case of a typical, hydrophysically, medical research {f 1 MHz, 1 ~ 10 cm, U 7 (water) is. 3-10 Pa. The minimum ampli tude pressure is determined by the dynamic range and noise level of the receiving path of the device implementing the method and for the above parameters is about 100 Pa. The main advantage of the method is the possibility of measuring with high accuracy without preliminary calibration of the receiving path, as well as its high noise immunity, since the measurement results are not affected by the acoustic wind in the medium, and the oscillator frequency fluctuations have practically no effect. It is also necessary to indicate the possibility of measuring in a pulsed mode, since an acoustic high-frequency pulse in a nonlinear medium behaves in the same way as a continuous wave, if in a pulse

51021954

many lengths are laid. The need for a continuous wave is sufficient, and the need to conduct such a negative pressure amplitude is often due to the fact that radiation causes cavitation.

Claims (1)

METHOD FOR ABSOLUTE DETERMINATION. The amplitude of the ACOUSTIC WAVE PRESSURE, which consists in the fact that a plane acoustic wave is excited in the medium, register an informative parameter at a frequency using a transducer? 'of the excited wave at two points of the medium, at a fixed distance E - one from the other in the direction of wave propagation, and from the measured parameters determine the pressure amplitude of the excited acoustic wave, characterized in that, in order to expand the range of measured pressure amplitudes and improve accuracy, as an informative parameter, the amplitudes of the signals received by the transducer are selected, they are measured at a double frequency of $ 2, and the pressure amplitude of the acoustic wave is calculated by the formula η p (PiMfP'H-pQzi.fP'ial e where p is the density of the medium, C is the speed of sound in the medium γ is the nonlinearity parameter of the medium / Ru, _and P ”are the measured values of the amplitude of ^{1 g} tone signals at the frequency £ (u = I) and 2 £ (h" 2) at the first and second points of reception. CZ with © Joint venture II 1021954 *