RU2537746C1 - Method of calibrating hydrophones by comparison - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: single-period tonal-pulsed signals with a Gaussian envelope are used as a tonal-pulsed signal in a standard method of calibrating hydrophones by comparison.

EFFECT: high accuracy of calibrating hydrophones by comparison using tonal-pulsed signals.

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Description

The invention relates to the field of hydroacoustics and can be used in the calibration of hydrophones (G) by comparison.

There is a method of calibration G by the comparison method, which consists in the location of the calibrated and reference hydrophones in the hydroacoustic basin at known distances Z _G and Z _E from the hydroacoustic emitter and irradiated with tonal-pulse input signals, the subsequent registration of output signals, the sensitivity M (t) _G calibrated hydrophone is determined by the formula: $$M{\left(t\right)}_G=M{\left(t\right)}_E\frac{\left|S{\left(t\right)}_G\right|}{\left|S{\left(t\right)}_E\right|}\cdot \frac{Z_G}{Z_E},\text{(one)}$$

where M (t) _E is the sensitivity of the reference hydrophone at a frequency F; S (t) _E , S (t) _G are the spectral coefficients of the discrete Fourier transform in the time interval 0-T of the output signals of the reference and graduated hydrophones, T is the time instant of arrival of the first reflected signal from the walls of the pool or water surface; Z _G , Z _E - the distance between the acoustic centers of the emitter and the calibrated and reference hydrophones, respectively (Bobber R.J. sonar measurements. Trans. From English. Ed. By A.N. Golenkov. M: Mir, 1974, p. 30 -38).

This method is adopted as a prototype.

The disadvantage of the prototype is the calibration errors associated with the presence of reflections of the tone-pulse signal supplied from the emitter to the hydrophone from structural elements of the hydrophone body, fairing and mounts, as well as from the surface of the water and pool walls.

Application of the Fourier transform of a tone-pulse signal allows one to reduce these errors, but does not exclude them at all.

The technical result obtained from the implementation of the invention is to increase the accuracy of calibration of hydrophones by comparison.

, в качестве тонально-импульсного сигнала используют однопериодный тонально-импульсный сигнал с гауссовой огибающей, где M(t)_Э - чувствительность эталонного гидрофона на частоте F; S(t)_Э, S(t)_Г - спектральные коэффициенты дискретного преобразования Фурье на временном промежутке 0-Т выходных сигналов эталонного и градуируемого гидрофонов, Т - момент времени прихода первого отраженного сигнала от стенок бассейна или поверхности воды; Z_Г, Z_Э - расстояния между акустическими центрами излучателя и градуируемого и эталонного гидрофонов соответственно.This technical result is achieved due to the fact that in the known method for calibrating hydrophones by the comparison method, which consists in arranging the calibrated and reference hydrophones in the hydroacoustic basin at known distances Z _G and Z _E from the sonar emitter and irradiating them with tone-pulse input signals, subsequent recording of output signals, while the sensitivity M (t) _{G of the} calibrated hydrophone is determined by the formula: $$M{\left(t\right)}_G=M{\left(t\right)}_E\frac{\left|S{\left(t\right)}_G\right|}{\left|S{\left(t\right)}_E\right|}\cdot \frac{Z_G}{Z_E}$$

, as a tone-pulse signal, a single-period tone-pulse signal with a Gaussian envelope is used, where M (t) _E is the sensitivity of the reference hydrophone at a frequency F; S (t) _E , S (t) _G are the spectral coefficients of the discrete Fourier transform in the time interval 0-T of the output signals of the reference and graduated hydrophones, T is the time instant of arrival of the first reflected signal from the walls of the pool or water surface; Z _G , Z _E - the distance between the acoustic centers of the emitter and the graduated and reference hydrophones, respectively.

The invention is illustrated by drawings. Figure 1 presents a diagram of the implementation of the method; figure 2, 3, 4, 5 are diagrams explaining the essence of the method.

The standard procedure for calibrating G by the method of comparison [1] is as follows.

The graduated and reference G are located at known distances Z _G and Z _E from the sonar emitter (I).

Then, using the circuit shown in Fig. 1, a tone-pulse signal is formed, which, after processing, is received by a calibrated and reference G. In this case, the sensitivity of Г is determined by the formula (1).

The transmission of the tone-pulse signal from And to the graduated and reference G is carried out using the circuit of figure 1, consisting of a master oscillator 1 (3G1), modulator 2 (M2), power amplifier 3 (UM3), reference generator 4 (OG4) and the shaper 5 (Ф5) pulses of a Gaussian shape. The electrical connections of the blocks are presented in figure 1.

Blocks 1, 2, 3, 4, 5 form a radiating path (IT6).

There is such a receiving and measuring path 7 (PT7), consisting of an output amplifier 8 (VU8), a band-pass filter 9 (PF9), a measuring amplifier 10 and an indicator 11 (I11).

The calibration process is reduced to measuring the output signals of the calibrated and reference Г, determining their Fourier transforms S (t) _Г and S (t) _Э and determining the sensitivity M (t) _{Г of the} hydrophone according to formula (1).

If only the free-field sensitivity module is needed, then the modules of the spectral coefficients of the discrete Fourier transform of the signals of the graded and reference G.

The free-angle phase angle of sensitivity for a graduated hydrophone is determined by the phase angles of the Fourier transform coefficients, taking into account the conditions for solving the ambiguity at a 180 ° phase.

The use of short (single-period) pulses with a Gaussian envelope (Fig. 2) to excite the emitter allows us to achieve the set technical result, since the spectrum (Fig. 3) of such a pulse is sufficiently smooth and wide, which makes it possible to use a radio pulse with one carrier frequency for calibrating hydrophones in wide range of frequencies.

This is confirmed by the experiment, the results of which are presented in figure 4, 5 in the form of signals taken from a graduated and reference G (figure 4), and their frequency spectra (figure 5).

In figure 4, at 12, the signal from the sensing element G is represented; at position 13 - reflection from the housing G and the mount; under position 14 - reflection from the bar.

Figure 5 under the positions 15, 16, 17 presents, respectively, the sensitivity of G without taking into account the reflections from the mount and rod G; sensitivity, taking into account reflections from the mount and housing G; sensitivity taking into account reflections from the mount.

Thus, the use of short tone-pulse signals when calibrating Г makes it possible to identify and efficiently tune from reflection sources, evaluate reflections from the Г housing, attachment points and rods, and take measures when designing equipment to eliminate them and reduce them to an acceptable level.

Claims (1)

A method for calibrating hydrophones by a comparison method, which consists in arranging a calibrated and reference hydrophones in a hydroacoustic basin at known distances Z _G and Z _E from a hydroacoustic emitter and irradiating them with tonal-pulse input signals, followed by recording output signals, while the sensitivity M (t) _{G of the} calibrated hydrophone is determined by the formula $$M{\left(t\right)}_G=M{\left(t\right)}_E\frac{\left|S{\left(t\right)}_G\right|}{\left|S{\left(t\right)}_{\mathrm{uh}}\right|}\cdot \frac{Z_G}{Z_{\mathrm{uh}}}$$

characterized in that as a tone-pulse signal using a single-period tone-pulse signal with a Gaussian envelope, where M (t) _E is the sensitivity of the reference hydrophone at a frequency f; S (t) _E , S (t) _G are the spectral coefficients of the discrete Fourier transform in the time interval 0-T of the output signals of the reference and graduated hydrophones, T is the time instant of arrival of the first reflected signal from the walls of the pool or water surface; Z _G , Z _E - the distance between the acoustic centers of the emitter and the graduated and reference hydrophones, respectively.

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