JPS61271476A - Sonar - Google Patents

Abstract

PURPOSE:To enable efficient and highly measurement of distance, by gauging relative distance between the target and a sonar based on the difference in the dependence on the frequency between a sound emission source spectrum and an audible sound spectrum. CONSTITUTION:An input sound wave 101 emitted from a target sound emission source is received with a receiver 1 and converted into an electrical signal to be fed to a receiver 2, the output of which is fed to a recording display circuit 1000 and an audible spectrum calculator 3. The calculator 3 calculates the difference due to frequency from an audible spectrum computed to be fed to a distance measuring device 4. A sound emission source spectrum generator 5 memorizes a sound emission source spectrum and data pertaining the coefficient of absorption loss over a specified frequency band beforehand and supplies the data to the measuring device 4. Then the measuring device 4 executes computation by a specified formula and outputs the results to the line 401 as measured distance. This facilitates the measurement of distance based on the difference between the sound emission source spectrum and the audible sound spectrum only through a wave receiving function.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a sonar device, and in particular has a function of receiving sound waves emitted by a target having a sound source with known frequency characteristics and also measuring the distance to the target. Equipped with sonar equipment f
j! Regarding t.

[Conventional technology]

Sonar devices are well known, and so-called passive sonar functions that receive sound waves emitted by a target and obtain information on the direction of the target, or passive sonar devices equipped with this function, are also well known. .

On various onboard platforms equipped with sonar devices equipped with such a wave receiving function, which receive sound waves emitted by targets while navigating underwater, the frequency of the sound source emitted by various ships navigating on or in the water is used. The spectrum is known based on many materials and experiments, and the received signal is also used for various operational purposes such as obtaining direction information related to the objective, identifying targets, etc. while referring to these known frequency spectra. has been done.

[Problem that the invention seeks to solve]

However, with conventional sonar devices of this type having a biased reception function, it is possible to obtain azimuth information, but it is essentially impossible to obtain distance information.

Therefore, if distance information between the target ship and the own platform is required, an active sonar device or an active sonar function is added and sent.

It can be measured from the time between receiving waves and the sound wave propagation speed, or it can be estimated by assuming the moving speed vector of the sound source and the moving speed vector of the target ship, and then moving the own ship in accordance with this moving speed vector. Several methods are being used, but either method requires the use of active sonar equipment with a complicated configuration and high detection ability, or results in inefficient estimation measurements with large errors. Blame the flaws.

It is also an object of the present invention to eliminate the above-mentioned drawbacks and provide a sonar device equipped with a wave receiving function capable of efficiently and highly accurate distance measurement.

[Friendly means of solving problems]

The device of the present invention is a sonar device that receives radiated sound waves from a target such as a ship having a sound source with a known frequency spectrum, and is capable of determining the frequency dependence between the frequency spectrum of the sound source and the frequency spectrum of a received signal. The sonar device is configured to include relative distance measuring means for measuring the relative distance between the target and the sonar device based on the difference.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of a sonar device according to the present invention. Receiver 2, auditory spectrum calculator 3. Also shown is a recording/displaying circuit 1000 which is configured to include a distance measuring device 4 and a sound source spectrum generator 5, and which records and displays a received signal similar to a normal passive sonar function.

An input sound wave 101 emitted by a target sound source is received by a receiver 1, subjected to acousto-electrical conversion, converted into an electrical signal, and supplied to a receiver 2 as a received signal.

The receiver 2 performs all predetermined band limiting, amplification processing, etc. on the received signal and then supplies it to the recording/displaying circuit 1000, whereupon the recording 9 display is performed through signal processing similar to that in a normal passive sonar function. It will be done.

The output of the receiver 2 is also supplied to an audible spectrum calculator 3, which calculates an audible spectrum.

The hearing spectrum is the frequency spectrum of the received signal,
It shows the characteristics of frequency and reception level over a preset frequency range. In this case, the received level is expressed as a time average value obtained through predetermined temporal statistical processing of the received signal, and short-term fluctuations in the received signal are almost eliminated. The predetermined time for performing such statistical processing is arbitrarily set in consideration of the purpose of operation of the sonar device, etc.

Now, the auditory spectrum obtained in this manner basically differs from the frequency spectrum of the target sound source in the following points.

In other words, the characteristics of the frequency spectrum of the sound source of the target ship, such as screw noise or noise emitted by the main engine or auxiliary equipment, have been almost clearly understood through many materials and experiments, but this is not the case when underwater. When it propagates and is captured by a sonar device, it suffers propagation loss, and absorption loss of this propagation loss has frequency dependence, meaning that the loss increases rapidly with frequency, so its frequency spectrum naturally changes. This results in a difference from the frequency spectrum of the sound source.

FIG. 2 is a spectral feature explanatory diagram for explaining the characteristics of the sound source spectrum and the auditory sound spectrum.

In this spectral feature explanatory diagram, the frequency (force is approximately 10KH)
The target is the so-called high frequency band from above Zz to several tens of KHz, and as is well known, the sound source spectrum in such a frequency band shows a level drop of approximately 6 dB/octave, which is represented by the solid line sound source. Spectrum S L
This is shown in (7).

Also, the hearing spectrum KLV1 is shown by a dotted line, and the diagonally shaded portion representing the difference between these two spectral characteristics is caused by absorption loss in the propagation loss, which will be described later. In FIG. 2, these two spectra are shown with the spectral level normalized at point P, and therefore the relative spectral levels are the same.

Now, for the propagation loss in the propagation of vocal tears in water, the following fi1 formula is often used as an approximation formula according to spherical diffusion without paying attention to any special propagation mode.

TL = 20]ogR+(!R・-=fll (In equation 11, TL is the propagation loss, R is the distance from the sound source to the sonar device, and 201ogR is the energy decrease as the sound wave diffuses as it propagates through the water. αR is an absorption loss due to attenuation due to water as a propagation medium.

The coefficient α of the absorption loss α is called an absorption loss coefficient and is a function of frequency and expressed in dB/Kyd (kiloyards). This frequency dependence due to α appears as a spectral difference between the audible sound spectrum and the sound source spectrum, as shown in FIG.

The explanation will be given again by returning to the embodiment shown in FIG.

The auditory spectrum calculator 3 calculates the following ΔB expressed by Equation 21 from the calculated auditory spectrum, and supplies this to the distance measuring device 4.

ΔR=)LL(fi)−KL(fj)
(2) fi and fj shown in equation (2) are two arbitrary frequencies.

Further, the source spectrum generator 5 stores in advance data regarding the sound source spectra 8L (, 4) over a predetermined frequency band, and also stores data regarding the absorption loss coefficient α for a predetermined frequency. α
uses a frequency determined in advance for operational purposes based on a known experimental formula.

The source spectrum generator 5 calculates the next ΔS and Δα shown by equation 41 (31°) corresponding to fi and fj specified each time the sonar equipment is operated, and supplies them to the distance measuring device 4.

ΔS = SL (fi) 8LCfj) ・・・Scream・
・(3) Δα=α(fi)−α(fj)...
(41) The distance w & can be obtained through calculation using the following equation (6).

B, = −(ΔS−ΔR) ・・・・・・・・・
...15) Δα The distance measuring device 4 executes the calculation according to equation (5) and outputs it as the measured distance to the output line 401, and thus the distance measurement based on the difference between the sound source spectrum and the hearing spectrum can only function as a wave receiving function. It can be easily implemented through

In addition, in this example, the lower limit of the frequency band used is 10KHz.
The frequency range and upper limit are intended for a so-called high frequency band of about several tens of kilohertz, but it is clear that this frequency band can be arbitrarily set in consideration of the operational purpose and the like.

〔Effect of the invention〕

As explained above, according to the present invention, in a sonar device that detects the radiated sound of a target such as a ship having a sound source whose frequency spectrum is known, the frequency spectrum of the memorized sound source and the frequency spectrum of the received signal can be Relative pressure between target and sonar device 111it based on dependence difference
- By providing a measuring means, it is possible to realize a sonar device that does not require the addition of an active sonar function and is capable of distance measurement that basically eliminates a decrease in accuracy due to estimation or the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of a sonar device according to the present invention, and FIG. 2 is a spectral feature explanatory diagram for explaining the characteristics of a sound source spectrum and an audible sound spectrum. 1...Receiver, 2...Receiver, 3...
... Auditory spectrum calculator, 4 ... Distance measuring device, 5 ... Sound source spectrum generator. Agent Patent Attorney Susumu Uchihara -1/ :,,
” Pa, de # 1 side 2nd figure

Claims (1)

[Claims] In a sonar device that receives sound waves radiated from a target such as a ship having a sound source with a known frequency spectrum, the frequency spectrum is determined based on the difference in frequency characteristics between the frequency spectrum of the sound source and the frequency spectrum of the received signal. A sonar device comprising a relative distance measuring means for measuring a relative distance to the sonar device.