RU2284485C2 - Method of determining underwater level of sound pressure in vessel frequency band - Google Patents

Abstract

FIELD: measuring technique.

SUBSTANCE: method comprises using hydroacoustic measuring system that is made of combined receiver mounted on the sea bottom. The combined receiver simultaneously measures hydroacoustic pressure P, Pa and vertical component of velocity variation Z, m/s in the frequency band, and the level of sound pressure G, db is determined from equation G = 20log₁₀(W^0.5/P₀), where P₀ = 20 μPa and W = a(P)² + b (Zρc)² + dP(Zρc) under condition that the mean value W for the vertically upward direction is equal to the mean value of value (P)² and d² ≠ 4ab, where ρ is the water density, kg/m³, c is the sound velocity in water, m/s, and a, b, d are the constant dimensionless coefficients.

EFFECT: simplified method and enhanced accuracy of measurements.

1 cl, 1 dwg

Description

The invention relates to measuring technique in the field of hydroacoustics and can be used to determine the level of underwater noise W _ν [Pa ² ] at a frequency ν [Hz] of an object passing over a hydroacoustic measuring system (GIS).

Known methods of the same purpose [1, 2], which consist of measuring the GIS sonar pressure P _ν [Pa] at a frequency ν and processing the information received.

Any of the known methods, for example, [2] can be taken as a prototype.

In the prototype, a sonar antenna made in the form of a hydrophone array is used as a GIS. In this case, a reference signal emitter is used to “calibrate” the surrounding space using hydroacoustic pressure. This makes it possible to compare the measured hydroacoustic pressure P _ν with the hydroacoustic pressure P _o generated by the reference hydroacoustic emitter taking into account the controlled distances L _u and L _o, respectively, from the well log to the underwater object and to the reference signal emitter, in each cycle of measuring the level of underwater noise. And then, by appropriate processing, determine W _ν .

The disadvantages of the prototype are the need for its implementation of a special emitter of reference signals, the complexity and bulkiness of the GIS used to measure P _ν , as well as measurement errors W _ν , determined by the reflection of the received signals from the bottom of the reservoir.

The technical result obtained from the implementation of the invention is the simplification and cheapening of the practical implementation of the method for determining the level of underwater noise, as well as improving the accuracy of measurements of W _ν .

This technical result is achieved due to the fact that in the known method for determining the level of underwater noise at a frequency ν of an object passing over a GIS, the hydroacoustic pressure P _ν at a frequency ν and processing the information obtained using the same GIS additionally measure the vertical component of the vibrational velocity Z _ν [ m / s] at a frequency ν, and the level of underwater noise W _ν is determined by the mathematical expression:

under the conditions that the average value of W _ν for the direction vertically upwards coincides with the average value of (P _ν ) ² and

where ρ [kg / m ³ ] is the density of water, s [m / s] is the speed of sound, and, b, s are constant dimensionless coefficients.

It is advisable to use a hydroacoustic combined receiver (KP) as a GIS.

The invention is illustrated in the drawing, which shows a diagram of the implementation of the method.

Object 1, for example, an underwater vessel, passes over the GIS 2, fixed on the seabed 3 of the water area 4.

GIS is a KP [3] having small wave sizes. GIS 2 is located at a depth h below the sea surface 5 and can measure the acoustic pressure P and the three components of the vibrational velocity ν (x _ν , y _ν , z _ν ). Signal processing units and recording equipment are not shown in the drawing.

These four parameters of underwater noise are measured by GIS 2 at the moment of passage by the noisy object 1 of the combined receiver installed on the bottom 3 of the reservoir.

Next, the processing of the signals obtained from the GIS 2 is carried out using algorithms (1) and (2). This allows for directions close to vertical (z axis), at each frequency ν of the analysis, to determine the amplitude and phase of the bottom-reflected signal 3, reduced to a plane passing through the center of GIS 2. As a result, the measurement error of hydroacoustic signals, determined by the reflection of the received signals from bottom 3.

When estimating the level of underwater noise W _ν passing to the GIS 2 from the direction, formula (1) and condition (2) obtained empirically are used. Under these conditions, of the three coefficients a, b, d, only two coefficients remain independent and free. By varying these two coefficients in the absence of other signals in the sea, in addition to the background noise of water area 4, we achieve a minimum of fluctuations in the value of W _ν .

Then, the found values of the three coefficients a, b, d are stored in the processing program. After that, GIS 2, made, for example, in the form of a combined receiver, becomes ready for use for measuring signals of low-noise underwater objects 1 by the known method of storing the signal maximum according to the technique applied, for example, in [4].

Thus, the use of a combined receiver for solving the task at hand, which allows simultaneously measuring four parameters of underwater noise at a frequency ν, and subsequent processing of the received signals using algorithms (1, 2), allows to increase the accuracy of measurements, as well as simplify and reduce the cost of underwater measuring equipment for implementation a known method for determining the level of underwater noise, which achieves the above technical result.

Information sources

1. RF patent No. 2063106, class. H 04 R 29/00, 1996.

2. RF patent No. 2010456, class. H 04 R 1/44, 1994 - prototype.

3. V. A. Gordienko, V. I. Il'ichev, L. N. Zakharov "Vector-phase measurements in acoustics." M., Science, 1986, pp. 77-79.

4. V.N.Danilov, A.A. Grushin "Special metrological support of hydroacoustic means". Petrodvorets, 1990, p. 48-79.

Claims (2)

1. The method of determining the underwater sound pressure level G [dB] in the frequency band of the vessel passing over the sonar measuring system by measuring the sonar pressure system P [Pa] in the frequency band and processing the received information, characterized in that using the same measuring system additionally measure the vertical component of the vibrational velocity Z [m / s] in the frequency band, and the sound pressure level G is determined by mathematical expression G = 20log ₁₀ (W ^0.5 / P ₀ ), where P ₀ = 20 μPa and where W = a (P) ² + b (Zρc) ² + dP (Zρc) under the conditions that the average value of W for the vertical direction coincides with the average value of (P) ² and d ² ≠ 4ab, where ρ [kg / m ³ ] is the density of water; s [m / s] is the speed of sound in water; a, b, d are constant dimensionless coefficients. 2. The method according to claim 1, characterized in that a combined receiver is used as a sonar measuring system.