SU1603286A1 - Method of measuring parameters of normal waves in acoustic waveguides - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the speeds of amplitudes and directions of propagation of normal waves in acoustic waveguides. The aim of the invention is to improve the measurement accuracy of the parameters of the propagation of normal waves in non-uniform along the path of the waveguides due to the exclusion of measurement errors associated with the change in speed along the waveguide path. The waveguide generates a set of reference frequency modulated signals with a linear frequency variation, which allows to take into account the change in the velocity of propagation of normal waves along the waveguide path. 1 il.

Description

i (L

The invention relates to a measurement technique and can be used to measure the speeds of amplitudes and directions of propagation of normal waves in acoustic waves.

The purpose of the invention is to increase the accuracy of measurement of the parameters of normal waves in waveguides that are not uniform along the route by eliminating measurement errors associated with the change in velocity along the waveguide path.

The drawing shows a block diagram of a device implementing a method for measuring parameters of normal waves in acoustic waveguides.

The device consists of the radiator 1, located in the waveguide 2 and connected to the output of the generator 3, /. sound receiver 4 connected via amplifier 5 to the inputs of synchronous detectors 6, generators 7 of the reference signal with linear-frequency modulation.

connected to the second inputs of synchronous detectors 6, and spectrum analyzers 8. connected to the outputs of the detectors 6. Moreover, the emitter 1 and the sound receiver 4 are mounted with the possibility of moving along the waveguide 2.

The method of measuring the parameters of normal waves in acoustic waveguides is carried out as follows.

With the help of radiator 1, in a non-uniform along the path waveguide 2 with a para- meter, slightly varying along the path, a sound field P with a frequency CO is excited. Moving the sound receiver 4 relative to the radiator 1 evenly with speed V, a signal of duration T is received, which is detected synchronously in synchronous detectors 6 with reference signals of generators 7 having linear frequency module 1 with the initial frequency W - o, deviation D and iemen -

are from to with pshgom no more than 2 and / t.

After detection, a signal is received and. In spectrum analyzers 8, the spectra of the detected signals are calculated. For each spectral component C; 2, the value of П „is determined, at which this component has a maximum value of C. This value corresponds to such a deviation at which, for a given normal wave, the change in the frequency of the received signal associated with the change in normal wave velocity, i.e.

i

Ug SOT

dCn

aZG

II, h

the + sign corresponds to the normal wave propagating in. positive direction

X axis and sign

at. against

opposite; With p - the speed of the normal wave.

After determining $ 7, r, the velocities, amplitudes and direction of wave propagation are found by the formulas

С „(Х)

. DhffX A - P

 T (FS) 2 p /

where AI is the amplitude of the normal wave. The direction of propagation is determined by the sign Cn, and selects 10

15

0

five

0

0

c, outcome of the maximum expected change in the velocity of normal waves.

Measurements using this method allow to take into account the change in the velocity of normal waves from the X coordinate.

Claims (1)

Invention Formula The method of measuring the parameters of normal waves in acoustic waveguides, concludes that a waveguide is excited at a frequency (j several normal waves in a continuous mode, the sound field is continuously recorded along the waveguide with a constant velocity of the measurement point relative to the emission point, generate a reference signal with frequency () - О, where o is the frequency of the reference signal, a synchronously measured and reference signal is detected, the frequencies and amplitudes of the spectral components of the detected signal are determined, They determine the speed, amplitude and direction of propagation of normal waves, characterized in that, in order to improve the measurement accuracy in non-uniform along the waveguides, they generate a set of reference frequency modulated signals with t linear variation of the modulation frequency and change of frequency deviation with a step of 2 if / T, where T is the duration of the received signal, measure the value of the deviation at which the spectral component has the maximum value of all spectra of the detected signals, taking into account which the claim is determined mye parameters.