RU1841358C - Device for monitoring ship noise emissions - Google Patents

Abstract

FIELD: hydroacoustic technology.

SUBSTANCE: invention relates to hydroacoustic technology, and more specifically to hydroacoustic devices for measuring and controlling the noise emission of ships. In addition, a sequentially connected absolute level determination unit containing the first multiplier and the first information storage device, and a noise emission level reduction unit containing the second multiplier and the second information storage device are introduced into the ship's noise emission control device, in each of the blocks, the first input of the multiplier is the input of the corresponding blocks, and the second input of the multipliers is connected to the outputs of the corresponding devices memorization. In this case, the input of the absolute level detection unit is connected to the output of the signal bias reduction unit, and the output of the noise emission reduction unit is connected to the input of the display and registration device.

EFFECT: technical result is to provide the possibility of measuring the reduced spectral level of the ship's noise emission in the sector of its aft heading angles.

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Description

The invention relates to hydroacoustic military equipment, and more specifically to hydroacoustic devices for measuring and monitoring the noise emission of ships, and is an improvement of the invention according to the author. St. No. 1841357 dated September 18, 1986.

As is known, the noise emission of ships, in particular submarines (especially in the stern heading angles), is an important tactical parameter that characterizes the secrecy of warships from the possibility of detection and direction finding by means of hydroacoustic weapons of a potential enemy. During acceptance tests and during combat use, the noise level of warships is measured. For this reason, identifying effective ways to solve the problem of noise measurement is relevant.

It is known "Device for monitoring the noise emission of a ship" by author. St. No. 1841357 dated 09.18.1986, which contains a flexible extended towed antenna (GPBA), a signal pre-processing device, an analog-to-digital conversion and digital information compression device, a spectrum analyzer and directional characteristics generator, a temporal and spatial processing device, a circuit for reducing the bias of signal estimates, a ship noise control circuit, a comparison circuit and an indication and registration device.

In this device, the first input of the circuit for reducing the bias of signal estimates is connected to the output of the device for temporal and spatial processing of the noise direction finding path with a GPBA corresponding to the directivity characteristic directed towards the towing ship, and the second input of this circuit is connected to the output corresponding to the directivity characteristic turned away from the ship - tugboat, and the output of the comparison circuit for making a decision about the permissible noise emission levels of the ship is connected to the input of the indication and recording device.

It provides a comparison of the current noise emission spectra of the ship with the spectrum recorded during acceptance tests, and the development of a decision, recorded on the indicator, about the admissibility of further combat use of the ship, depending on whether or not the current spectrum recorded during acceptance tests exceeds or not. This ensures control of the noise of the ship during its combat use. However, information only about the relative value of the noise emission spectrum of a ship is insufficient for judging the value of the reduced spectral level of noise emission, since it does not take into account the transfer functions of the propagation medium of signals emitted by the ship and the receiving path with a flexible extended towed antenna.

The purpose of this invention is to provide the ability to measure the reduced spectral level of noise emission from a ship in the sector of the aft heading angles.

This goal is achieved by introducing into the device according to the main invention a series-connected circuit for determining the absolute level and a circuit for reducing the level of noise emission, each of which contains a multiplier and an information storage device, input information is supplied to the first input of the multiplier, and information from the storage device is supplied to the second input, wherein the input of the circuit for determining the absolute level is connected to the output of the circuit for reducing the bias of signal estimates, and the output of the level reduction circuit is connected to the indication and recording device.

In the scheme for determining the absolute level, the estimate of the spectral density of noise emission is multiplied by the reciprocal of the square of the product of the end-to-end transmission coefficient of the path and the sensitivity of the antenna receiver. As a result, we have an estimate of the spectral density of noise emission measured in the acoustic field at the location of the GPBA. In the level reduction scheme, this estimate is multiplied by a reduction coefficient equal to the signal propagation losses from the source to the GPBA, which gives the required estimate of the reduced spectral level of noise emission of the ship in the sector of the aft heading angles.

The authors and the applicant are not aware of technical solutions containing similar distinctive features. Therefore, we can assume that the proposed technical solution satisfies the “Substantial differences” criterion.

The essence of the proposed device is illustrated in the following graphic figures:

fig. 1 - block diagram of a device for monitoring the noise emission of a ship according to ed. date No. 1841357;

fig. 2 - block diagram of a device for measuring noise emission from a ship.

The proposed device consists (see Fig. 2) of a flexible extended towed antenna 1, the hydrophone outputs of which are connected to the inputs of a signal pre-processing device 2, which provides signal amplification and filtering, the outputs of this device are connected to the inputs of an analog-to-digital conversion and information compression device 3 The information converted into digital form and compressed is supplied via a towing cable to the digital information decompression and storage device 4, the outputs of which are connected to the inputs of the spectrum analyzer and directional characteristics generator (XN) 5, the outputs of which, in turn, are connected to the inputs of the temporary and spatial processing 6. Two outputs of this device are selected - one corresponds to the CV directed towards the towing ship, the second corresponds to the CV turned away from the towing ship. Both outputs are connected to two inputs of the signal estimation bias reduction circuit (SSOS) 8, the output of which is connected to a series-connected ship noise emission control circuit 9 and a comparison circuit 10, the output of which is fed to the display and recording device 7. From the output of the SSOS circuit 8, a signal is supplied to a series-connected absolute level determination circuit 11 and a level reduction circuit 12, the output of which is connected to an indication and recording device 7, where the results of measuring the reduced spectral noise emission level of the ship are displayed. The absolute level determination circuit 11 contains a first multiplier 11a and a first storage device 11b. The first input of the multiplier 11a receives a signal from the SSOS circuit 8, the second - a signal from the storage device 11b, which is the reciprocal of the square of the product of the transmission coefficient of the receiving path and the sensitivity of the GPBA hydrophone. The level reduction circuit 12 contains a second multiplier 12a and a second storage device 12b. The first input of the multiplier 12a receives a signal from the absolute level determination circuit 11, the second - a signal from the storage device 12b, which is the value of the propagation loss of noise radiation from the towing ship to the towed antenna.

The practical implementation of the blocks of the proposed device is known from the technical literature. In particular, the practical implementation of blocks 1-10 is described in the description of the author. date No. 1841357 dated September 18, 1986.

The execution of the newly introduced blocks is also known from the technical literature. Multipliers 11a and 12a are digitally implemented using a set of logic elements in an integrated design (see the books Semiconductor Circuitry, U. Titze, K. Schenk, M.; Mir, 1983, fig. 19.38, pp. 339-341; Digital Filters and their application, V. Cappellini, A. J. Konstantinidis, P. Emiliani, M.: Energoatomizdat, 1983, Fig. 7.7; Theory and application of digital signal processing, L. Rabiner, B. Gould, M.: Mir, 1978 , Fig. 8.29). In analog form, multipliers are implemented in an integrated design (see the book “Analog and Digital Integrated Circuits,” edited by S.V. Yakubovsky, M.: Soviet Radio, 1979, Fig. 4.17). Storage devices 11b and 12b are ordinary memory blocks or long-term storage devices (LDS), which are a mandatory element of any computer (see, for example, Production Automation and Industrial Electronics, volume 1, M.: Soviet Encyclopedia, 1964, pp. 407, 412 , 413).

The operation of the proposed device is carried out as follows. GPBA 1 (see Fig. 2) receives acoustic noise mixed with noise emission from the ship. The signals received by the GPBA hydrophones are amplified and filtered in signal pre-processing block 2. Then, the ADCs are sequentially interrogated through the switch and converted into digital form. This is done in the analog-to-digital conversion and digital information compression device 3. The compressed digital signals are transmitted via a cable tow to the decompression and storage device 4, where they are stored before further processing. They are then subjected to a two-dimensional fast Fourier transform in the XN 5 spectrum analyzer and shaper. FFT operations are carried out first on the temporal realizations in each channel, and then on the spatial realizations at each frequency point. The result is a spatial-frequency spectrum of acoustic signals equivalent to a static CN fan at each of the frequency points of their narrow-band frequency spectrum. For sequentially obtained implementations of the spatial-frequency spectrum, the squared modulus of the spectral components is calculated and averaged in the temporal and spatial processing block 6, the resulting estimates of the power spectral densities are displayed on indicator 7.

From the generated CNs at the outputs of the temporal and spatial processing device 6, two CNs are selected - “aimed” at the ship and “turned away” from the towing ship. The first CN contains an estimate of the spectral power density of the ship's noise mixed with the spectral density of interference on the GPBA

in the second CN - only an estimate of the spectral power density of the interference on the GPBA

In this case, the interference in the two CNs is approximately the same in spectral densities and is not correlated with each other.

Both estimates are received synchronously at the inputs of the SSOS - 8 circuit. In the SSOS, subtraction and additional averaging of spectral density estimates are carried out

magnitude is an estimate of the spectral density of the signal-noise emission of the ship towing the gas propulsion vessel, “cleared” of the constant component of interference.

The signal from the SSOS is fed to the input of the absolute level determination circuit 11, in the first multiplier 11a of which it is multiplied by the value , which is the reciprocal of the square of the product of the end-to-end transmission coefficient of the path on the sensitivity of the GPBA receiver γ

Path transmission coefficients and sensitivity γ in existing samples of systems with GPBA are constant values. For this reason, the value is stored in the first storage device 11b. Thus, the value is an estimate of the spectral density of the noise emission of the towing ship, measured in the acoustic field at the location of the GPBA.

Next signal is transmitted to the level reduction circuit 12, where in the second multiplier 12a it is multiplied by the reduction coefficient P, equal to the loss of noise emission propagation from the towing ship to the receiving GPBA

The value P is stored in the second storage device 12b. When determining it, the following considerations were taken into account:

- the distance r from the towing ship to the phase center of the GPBA is fixed and known;

- reception of noise emission is carried out by the CN, “aimed” at the ship, so only a direct beam is received with detuning from the rays reflected from the surface and bottom;

- the distance r is relatively small (does not exceed 1 km), while refractive effects do not yet appear.

Under such conditions, the reduction coefficient P = r ² , since when propagating along a direct beam, the signal diverges according to a spherical law.

The resulting value is an estimate of the power spectrum of the noise emission of the towing ship, reduced to a unit distance. It is displayed on the display and recording device 7.

The technical effect of using this technical solution is that the proposed device ensures the use of a device according to the main invention, and therefore a noise direction-finding system with GPBA to solve a new problem of operational measurement of the reduced noise emission level of the carrier ship in the sector of the aft heading angles in combat conditions.

It is intended to use the proposed device in the development of promising systems with GPBA for submarines at the applicant enterprise. At the same time, it will allow them to solve a new task assigned to them - measuring the noise of the carrier.

In modern paths of systems with GPBA, the spread of sensitivity of antenna receivers is ±2 dB, and the spread of amplitude-frequency characteristics of the path channels ranges from ±2 to ±4 dB, i.e. the spread of characteristics of elementary channels can be ±6 dB. However, during the formation of CN, this spread is reduced due to averaging over channels in times, where N is the number of channels, i.e. will be about ±2 dB. This error value can be considered as the instrumental accuracy of the proposed device. The additional error associated with bringing the noise emission level to a unit distance can be estimated at a maximum of 6 dB (in the case when the width of the CN “aimed” at the towing ship is insufficient to detune from the beam reflected from the surface). In this case, the total maximum measurement error will be 6-8 dB.

Thus, the goal set for this invention is fully achieved.

NAMES OF BLOCKS IN THE FIGURES OF THE GRAPHIC IMAGE

1. Flexible extended towed antenna.

2. Signal pre-processing device.

3. Device for analog-to-digital conversion and information compression.

4. Device for decompressing and storing digital information.

5. Spectrum analyzer and directional characteristics generator.

6. Temporal and spatial processing device.

7. Device for indicating and recording results.

8. Scheme for reducing the bias of signal estimates.

9. Scheme for monitoring ship noise emissions.

10. Comparison scheme.

11. Scheme for determining the absolute level.

11a. First multiplier.

11b. The first storage device.

12. Level reduction scheme.

12a. Second multiplier.

12b. Second storage device.

Claims (1)

A device for monitoring the noise emission of a ship according to author's certificate No. 1841357, characterized in that, in order to ensure the possibility of measuring the reduced spectral level of noise emission of a ship in the sector of its aft heading angles, it is additionally equipped with a series-connected absolute level determination unit containing a first multiplier and a first device storing information, and a block for adjusting the noise emission level, containing a second multiplier and a second information storage device, in each of the blocks the first input of the multiplier is the input of the corresponding blocks, and the second input of the multipliers is connected to the outputs of the corresponding storage devices, and the input of the absolute level determination block is connected to the output block for reducing the bias of signal estimates, and the output of the block for reducing the noise emission level is connected to the input of the indication and recording device.

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