RU1778586C - Method for graduating pressure gradient receivers - Google Patents

Abstract

The invention relates to measuring technique and can be used to calibrate pressure gradient receivers by comparing with a reference hydrophone near a sound emitter in a zone of spherical wave propagation. The goal is to increase the accuracy of determining the sensitivity of the hydrophone. The goal is achieved in that the calibrated and reference hydrophones placed in the middle of the water layer are located at a distance selected from the condition r 3R + L / 2, where R is the radius of the spherical sound emitter; L is the effective length of the pressure gradient receiver. Then, in the final results of the sensitivity calculation, the correction for spherical wave propagation is determined by the formula -T V Ј 5V7Dr where K 2 / A is the wave number. The correction takes into account the dependence of the increase in pressure drop on the effective length of the pressure gradient receiver and allows obtaining more accurate sensitivity values when calibrating at small distances to the sound emitter. 1 ill. THX

Description

The invention relates to the field of measurement technology and can be used to calibrate sound pressure gradient receivers.

A known method for calibrating pressure gradient receivers near a spherical wave emitter. This method allows calibration of pressure gradient receivers by a simple and common method of comparison with a reference hydrophone in the field of spherical wave propagation. The use of pulsating sphere emitters can significantly reduce the size of the Fresnel zone of the emitter and calibrate the pressure gradient receivers at distances to the emitter, which are comparable to the effective sizes of the receivers. However in

In this case, calibration by the indicated methods will lead to erroneous results, since the correction for spherical wave propagation used in them was obtained under the condition that the pressure gradient of the sound wave Lp / Og in the receiver phase center is equal to the differential pressure of the sound wave DR over the effective length L of the calibrated receiver, which is violated as the distance from the receiver to the sound emitter decreases. .

As a prototype, the calibration method was chosen, namely, that the calibrated pressure gradient receiver is placed in a liquid, the liquid is brought into oscillatory motion and the voltage at the outputs of the receiver is measured and calculated

vi vi

00

ate

00 Pts

receiver sensitivity according to a known dependence.

The disadvantage of this method is that when calibrating the receivers, errors arise in determining the sensitivity of the receiver.

The purpose of the invention is to increase the accuracy of determining the sensitivity of pressure gradient receivers.

The goal is achieved by immersing a spherical sound emitter and a reference hydrophone in a liquid, a pressure gradient receiver and a reference hydrophone located in the middle of the water layer at a distance r between the centers of the pressure gradient receiver and a spherical sound emitter, selected from the condition 3R + L

g

2

(D

where R is the radius of the spherical sound emitter;

L is the effective length of the pressure gradient receiver,

measure the voltage at the outputs of the receiver and hydrophone and calculate the sensitivity of the receiver, and the correction for spherical wave propagation taken into account in the final results is determined by the formula

r2

V iv 1 4- (L v

Y)

r2

-fM2 2

2l

2g

1

(2)

tg

2 KL

where K y is the wave number;

I am the wavelength of sound.

Placing the pressure gradient receiver at a distance r (1) from the center of the sound emitter avoids the intersection of the effective dimensions of the receiver and sound emitter, which leads to distortion of the sound velocity streamlines, and eliminates the mutual influence of the graduated receiver and sound emitter. The location of the pressure gradient receiver near the sound emitter causes the change in the pressure gradient of the sound wave over the effective length of the graduated receiver to be non-linear. In this case, the pressure drop along the length of the graduated receiver differs from the pressure gradient in its center, and the representation of the graduated receiver as a point leads to an error in determining its sensitivity. The introduction of amendment (2) on the spherical propagation of waves depending on the final dimensions of the graduated receiver makes it possible to take into account the displacement of the location point of the average pressure drop over the length of the receiver

pressure gradient from its geometric center and to avoid errors in determining the sensitivity of pressure gradient receivers when calibrating them in the zone of spherical wave propagation at distances to the sound emitter, comparable with the effective sizes of pressure gradient receivers. The distance r chosen from condition (1) and included as an argument in

10, amendment (2), is measured between the geometric centers of the pressure gradient receiver and the sound emitter.

The method for calibrating pressure gradient receivers is illustrated in the drawing.

15 Position the calibrated receiver 1 and the model hydrophone 2 in the middle of the water layer at a distance r satisfying condition (2), establish the required frequency and amplitude of the emitted signal between the centers of the sound emitter 3 and the calibrated receiver, 20 measure the directivity of the calibrated receiver, orient axis of maximum sensitivity graduated

25 receivers per sound emitter, measure the voltages at the outputs of a graduated receiver and a reference hydrophone, calculate the correction value (2) for the spherical wave propagation for data and L and

30 determine the sensitivity of a pressure gradient receiver at a given frequency.

The application of correction (2) for the spherical propagation of waves under condition (1) allows

Over a wide frequency range, calibration of pressure gradient receivers by comparing with an exemplary hydrophone at a distance to a sound emitter comparable to the effective sizes of graduated receivers.

Formulation Method for calibrating pressure gradient receivers by immersing a graduated pressure gradient receiver in

45 liquid and bringing the liquid into vibrational motion, characterized in that, in order to increase accuracy, a spherical sound emitter and a reference hydrophone are immersed in the liquid, while the pressure gradient receiver and the reference hydrophone are placed at the same distance g from the center of the spherical sound emitter, which is selected from the condition + L

55 g - 2

where L is the effective length of the pressure gradient receiver;

R is the radius of the spherical sound emitter,

- / T, f L ч2 T

g2 - (L / 2) 2 1 + (2 2

51778586

then measure the output at the same time

pressure gradient receiver and V signals

reference hydrophone, with respect to - tg

the sensitivity of the pressure gradient receiver is determined, and 5 is determined where K is the wave number; multiplicative correction ty to the sensitivity of the pressure gradient receiver by the ratio

I am the wavelength of sound.

- / T, f L ч2 T

g2 - (L / 2) 2 1 + (2 2 KL

- tg

K - wave number

I am the wavelength of sound.

the general

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