RU2541682C1 - Method of analysis of acoustic field of complex source - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: after bandpass filtering received signals are saved, and then reproduced many times, besides, in each cycle of reproduction the received signals and signals with multiplied frequencies are retained in each channel for the time of acoustic wave propagation from the controlled point of the field to the appropriate receiver of a discrete antenna. Afterwards they save the result of multiplication of enveloping signals produced after detection of signals for controlled points of the field. Measurement of coordinates of controlled points of the field in the next cycle of reproduction and registration of a combination of measurement results make it possible to produce estimate of intensity of the acoustic field specified by radiation of the complex source.

EFFECT: making it possible to search for dominant zones of an acoustic field without relative displacement of a complex source and a receiving system, which simplifies measurement process.

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Description

The invention relates to measuring equipment and can be used to search for areas of increased acoustic radiation along the length of vehicles - in automobile or railway transport, as well as on ships for various purposes during their diagnostic examination.

A known method of additive directional reception, based on the use of interference of signals from the outputs of individual receivers when a wave is incident on an antenna from an acoustic source (See: A. Novikov, Statistical Measurements in Ship Acoustics. L .: Sudostroenie, 1985, p. 263 -266).

The essence of the method is illustrated by the example of tests of moving vehicles when the vehicle passes at a close distance from the receiving system of the measuring transducers. The basis of the method is the determination of sound pressure due to sources of acoustic field - various vibroactive mechanisms distributed along the length of the test vehicle. In this case, the position of the sound source (noise of machines and mechanisms), and therefore the position of the energy source of the hydroacoustic field, is determined by comparing the maximums of the total sound pressure with those parts of the vehicle that, at the time of the occurrence of these maximums, are in the alignment of the radiation pattern of the individual receiver system.

The disadvantage of this method is that the distance between the receiving elements of the directional system must be less than half the wavelength of the received signal. When searching for areas of increased acoustic radiation of an extended measurement object, the resolution of the method is determined by the aperture of the antenna.

The closest in technical essence to the proposed solution is the method of directional reception, based on the use of interference of signals taken from the outputs of individual receivers when an acoustic wave is incident from the source upon an antenna, followed by multiplying the frequencies of the received signals, summing the original signals, summing the signals with multiplied frequencies and multiplying the sum of the signals obtained as a result of detection (see the patent of the Russian Federation No. 2478982, IPC G01S 15/00, 2011, Garin V.Yu., Stefansky V.M.). This method of determining sound pressure is taken as a prototype. When searching for zones of dominant acoustic radiation from the measurement object, relative movement of the receiver system and the extended source of the acoustic field is necessary.

The essence of the prototype method for an additive antenna in receive mode is reduced to the following operations:

1) multichannel reception of radiation signals;

2) filtering the received signals at high radiation frequencies;

3) the frequencies of the received signals are multiplied by the number of times corresponding to the number of receivers in the system;

4) the summation of the source signals;

5) the summation of signals with multiplied frequencies;

6) the envelope of the sum of the signals with the initial frequencies is highlighted by amplitude detection;

7) the envelope of the sum of signals with multiplied frequencies is extracted by amplitude detection;

8) the envelopes of the sums of the signals are multiplied;

9) the result of multiplying the sums of the signals is recorded.

In the latter case, the search for the maximum result of multiplying the sum of the signals with the original frequencies and the sum of the signals with the multiplied frequencies corresponding to the position of the sound source along the length of the vehicle is performed as a result of the relative motion of the vehicle and the stationary receiving system.

The disadvantage of the prototype method is the need for relative movement of the measurement object and the receiving system. For measurement conditions in limited waters, for example, in a hydroacoustic basin, this mode is not feasible.

The objective of the invention is to enable the search for dominant zones of the acoustic field without the relative movement of a complex source and receiving system, which simplifies the measurement process.

This is achieved by the fact that after bandpass filtering, the received signals are stored and then the method operations are repeatedly reproduced with them, and in each playback cycle, the received signals and signals with multiplied frequencies are delayed in each channel for the duration of the propagation of the acoustic wave from the controlled field point to the corresponding discrete receiver antennas. After that, the result of multiplying the envelopes of the signals obtained after detecting the signals for the controlled points of the field is stored. Changing the coordinates of the controlled field points in the next playback cycle and recording the totality of the measurement results allow us to estimate the intensity of the acoustic field due to the radiation of a complex source.

The essence of the proposed technical solution is illustrated by figures, where:

figure 1 presents the structural diagram of a device that implements the proposed method;

figure 2 presents a planar radiation pattern of the antenna with a petal directed to the center point of the field formed by a complex source;

figure 3 presents a planar radiation pattern of an antenna with a petal directed to the center point of the field formed by a complex source, obtained by multiplying two diagrams: a radiation pattern constructed from received signals and a radiation pattern constructed from signals with multiplied instantaneous frequencies.

figure 4 presents a planar radiation pattern of the antenna focused at a given point in the analyzed field, obtained before multiplying the frequency of the signals in each receiver;

figure 5 presents a planar radiation pattern of the antenna focused at a given point in the analyzed field after multiplying the frequency of the signals in each receiver;

figure 6 presents a three-dimensional image of the resulting planar radiation pattern of the antenna obtained by the proposed method;

figure 7 presents a three-dimensional characteristic obtained by the interaction of the directed properties of the antenna, formed by the proposed method, and the acoustic field due to radiation from a complex source.

A device that implements the proposed method (see Fig. 1) contains a receiver unit 1 connected through a bandpass filter unit 2 to a storage device 3, the output of which is connected to the input of the first delay unit 4 and the frequency multiplication unit 5 connected to the input of the second delay unit 6, and the outputs of the delay units 4 and 6 are connected to the inputs of the adders 7 and 8, the outputs of which are connected to the inputs of the detection and multiplication unit 9, the output of which is connected to the input of the recorder 10, and the output of the delay units 4 and 6 is connected control 11.

Using the described device, the proposed method is implemented as follows.

The input signal is received by the receiver unit 1, which is considered a discrete antenna, consisting of discrete measuring transducers - microphones or hydrophones. After band-pass filtering of the signals taken from the outputs of the measuring transducers of the receiver unit 1, in the filter unit 2, the signals are stored in the memory 3 and, when reproduced, are multiplied by the frequency in the frequency multiplication unit 5. Then they are delayed in blocks 4 and 6 by the propagation time acoustic waves from the controlled field point to the corresponding receiver of the discrete antenna and their summation in the adder 7. This operation allows you to focus the radiation pattern on the controlled point a an oral field formed by a complex source. The calculation of the required delays for the delay units 4 and 6 is carried out using the control device 11. After multiplying the frequency in the frequency multiplying unit 5 and summing the signals with the multiplied frequencies in the adder 8, a radiation pattern is formed, characterized by the appearance of side lobes equal in magnitude to the main one. The signals from adders 7 and 8 are detected and multiplied in the detection and multiplication unit 9. As a result of this operation, the influence of the side lobes is suppressed, and the resulting radiation pattern provides increased spatial resolution. As a result, the distribution of the amplitudes of the resulting signals is formed for the set of controlled points of the field of a complex source.

Consider an example of computer simulation of a device that implements the proposed method.

As a result of the simulation, the signals observed at the output of the antenna, consisting of nine equidistant receiving elements, from a point monochromatic emitter moving relative to the antenna receivers at different distances were calculated. As a result of the scan, a traditional planar radiation pattern is formed, an example of which is shown in FIG. Figure 3 presents a planar radiation pattern of an antenna with a lobe directed to the center point of the field formed by a complex source, obtained by multiplying two diagrams: a radiation pattern constructed from the received signals and a radiation pattern constructed from signals with multiplied instantaneous frequencies. As in the prototype method, the frequency is multiplied by highlighting the instantaneous amplitude and instantaneous phase of the signal with its multiplication by a specified number of times. In this case, the instantaneous frequency is multiplied. For this purpose, the Hilbert transform of a narrow-band signal and the modulation of the harmonic signal at the middle frequency of the band-pass filter in amplitude and phase after its multiplication are used. The use of the prototype method allows to increase the efficiency of directional reception for various frequencies without changing the aperture of the antenna, but does not provide the ability to analyze its spatial structure. The introduction of the required delays in the device according to the prototype method and in the device according to the proposed method (figure 4) allows you to focus the discrete antenna at an arbitrary point on the field. Figure 5 shows an example of a planar radiation pattern with increased spatial resolution, the main lobe of which is directed to a given point in the field. Figure 6 as an example shows a three-dimensional image of a planar radiation pattern obtained by the proposed method.

The effectiveness of the proposed method is confirmed by the results of the following model experiment.

The source of the tonal signal at a frequency of 1000 Hz moved within a plane limited by the dimensions X = ± 10 m and Y = ± 10 m. The signal under study was received by an antenna of 9 receiving elements located on a circle. The distance between the receiving elements was 0.75 m. The distance between the axis of the antenna and the plane in which the source moved was 8 m. The signal amplitude at the antenna output was estimated every 0.2 m. As a result of the joint presentation of the measurement data, a planar radiation pattern was constructed . The receiving elements of the antenna were affected by signals due to the work of 5 emitters located within a square of 2 m × 2 m.

7 shows the result of the interaction of the directional properties of the antenna, formed by the proposed method, and the acoustic field due to radiation from a complex source.

The simulation showed that the use of new operations in accordance with the proposed method for the analysis of the acoustic field made it possible to determine the position of the dominant radiation zones within a given plane.

The main advantage of the proposed method for determining sound pressure over the prototype method is that a change in the sensitivity of the receiving system in space is achieved by introducing compensation delays in the channel paths of individual receivers. In this case, the relative movement of the complex source relative to the receiving system is not required.

Claims (1)

A method for analyzing the acoustic field of a complex source, including synchronous multichannel reception of hydroacoustic signals using a discrete antenna from equidistant receivers, band-pass filtering of received signals in each channel, multiplying the instantaneous frequencies of the received signals by the number of receivers in the discrete antenna, summing the received signals, summing the signals with multiplied instant frequencies, amplitude detection of the total signals, multiplication of the detection results and registration of the resulting signal after multiplying the detected signals, characterized in that, after filtering, the received signals are stored and repeatedly reproduce the method operations with them, and in each playback cycle, the received signals and signals with multiplied instantaneous frequencies are delayed in each channel for the duration of the propagation of the acoustic wave from the controlled field point to the corresponding discrete antenna receiver, after which the result is recorded in a known manner.

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