JPH04335119A - Apparatus for detecting underwater acoustic signal - Google Patents

Abstract

PURPOSE:To facilitate the recognition of the presence of a sound emitting source. CONSTITUTION:Two wave receivers 11 and 12 receive the synthesized sound of the sound of a sound emitting source and underwater noises. The frequency of the received signal is analyzed in corresponding Fourier transformation parts 13 and 14. The result is inputted into corresponding spectrum removing parts 15 and 16. All spectrums other than the specified frequency spectrum are made to be 0. The output of the spectrum removing part 15 becomes a conjugate complex signal in a conjugate complex part 17. The output of the conjugate complex part 17 and the output of the spectrum removing part 16 are synthesized in a complex multiplying part 18. Correlation is obtained in a reverse Fourier transformation part 19. The result is displayed on a display part 20 as one signal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater acoustic signal detection device for detecting spike signals emitted by sound sources located underwater.

0002

2. Description of the Related Art A conventional underwater acoustic signal detection device is constructed as shown in FIG. 3, for example. In FIG. 3, the receiver 3
1, a sound wave that is a combination of a spike signal emitted by an underwater sound source and underwater noise is received. The received wave output of the receiver 31 is frequency-analyzed by the Fourier transform section 32, and the frequency spectrum is displayed on the display section 33 in the format illustrated in FIG. In Figure 4, the sound source has n frequencies (f1, f
2, ..., fn), where the horizontal axis is the frequency and the vertical axis is the level of each frequency spectrum.

0003

[Problems to be Solved by the Invention] In the conventional underwater acoustic signal detection device described above, when a sound source generates n spike signals, each is detected as an independent signal. There is a problem in that it may be difficult to recognize.

That is, the resolution of frequency analysis in the Fourier transform unit, that is, the average power of underwater noise within the frequency bandwidth Δf is N, and the power at the reception point of each frequency of the sound source is S1.
, S2, ..., Sn, the signal-to-noise ratio (S/N) of the analysis result for each frequency is approximately S1 /N.
, S2 /N, ..., Sn /N, but recognition of the existence of the sound source is difficult because it depends on whether the maximum value of S1 /N to Sn /N is at a recognizable level. There are cases.

SUMMARY OF THE INVENTION An object of the present invention is to provide an acoustic signal detection device that facilitates recognition of the presence of a sound source.

[0006]

Means for Solving the Problems In order to achieve the above object, an underwater acoustic signal detection device of the present invention has the following configuration. That is, the underwater acoustic signal detection device of the present invention includes two receivers that receive spike signals emitted from sound sources existing underwater; and Fourier transform of corresponding received wave outputs of the two receivers. two Fourier transform units for processing;
two spectrum removal units that receive outputs from corresponding ones of the two Fourier transform units and convert all spectra other than the externally instructed frequency spectrum or frequency spectra in the vicinity thereof to 0; the two spectrum removal units; a conjugate complex part that generates a conjugate complex number of the output of one of the parts; a complex multiplication part that calculates the product of the output of the other of the two spectrum removal parts and the output of the conjugate complex part; about the output of the complex multiplication part The present invention is characterized by comprising: an inverse Fourier transform section that performs an inverse Fourier transform process; and a display section that displays an output of the inverse Fourier transform section.

[0007]

[Operation] Next, the operation of the acoustic signal detection device of the present invention constructed as described above will be explained. From the frequency analysis of the synthesized sound of the sound source and underwater noise received by each of the two receivers, the frequency spectrum specified from the outside (the one assumed to be possessed by the target) )
Alternatively, only frequency spectra in the vicinity thereof are extracted and synthesized, and detected and displayed as one signal. In other words, since all the spike signals emitted by the sound source are effectively utilized and all the energy is extracted, the S/N is improved compared to the conventional method. As a result, the presence of the sound source can be easily recognized.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an acoustic signal detection device according to an embodiment of the present invention. In FIG. 1, two receivers 11 and 12 are placed at positions apart from each other, but each receives a synthesized sound of the sound of the sound source and underwater noise. The received wave output of this receiver 11 (12) is transferred to the Fourier transform unit 13 (14).
The frequency is analyzed in , and input to the spectrum removal section 15 (16).

Since the spectrum removing unit 15 (16) is provided with spectra of a plurality of frequencies assumed to be possessed by the target from the outside, the spectrum removing unit 15 (16) removes the frequency spectrum that is frequency-analyzed by the Fourier transform unit 13 (14). , spectra other than the externally specified frequency spectrum or frequencies other than those in the vicinity thereof are set to 0 and output. The output of this spectrum removal unit 15 (16) is a complex signal, and the output of one spectrum removal unit 15 is the conjugate complex part 1
7, where it becomes a conjugate complex signal.

[0010] The complex multiplier 18 performs complex multiplication of the output of the conjugate complex unit 17 and the output of the other spectrum removal unit 16. The output is subjected to inverse Fourier transform in an inverse Fourier transform section 19 and displayed on a display section 20.

Here, the output of the inverse Fourier transform section 19 is:
Of the frequency spectrum of the synthesized sound of the sound of the sound source and the underwater noise received by the two receivers, the correlation output is based only on the spectrum of the externally specified frequency or the spectrum of frequencies in the vicinity thereof. Therefore, the display on the display unit 20 is as follows.
For example, as shown in FIG. 2, it is displayed as one signal. In FIG. 2, the horizontal axis represents the arrival time difference between the sounds of the sound generation sources reaching the two receivers, and the vertical axis represents the correlation output.

0012

[Effects of the Invention] As explained above, according to the underwater acoustic signal detection device of the present invention, a plurality of spike signals emitted by a sound source can be detected as one signal from underwater noise in a wide frequency band. Therefore, the existence of the sound source can be easily recognized.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram of an underwater acoustic signal detection device according to an embodiment of the present invention.

FIG. 2 is a diagram of a display example on the device of the present invention.

FIG. 3 is a configuration block diagram of a conventional underwater acoustic signal detection device.

FIG. 4 is a diagram of a display example in a conventional device.

[Explanation of symbols]

11 Receiver 12 Receiver 13 Fourier transform section 14 Fourier transform section 15 Spectrum removal section 16 Spectrum removal section 17 Conjugate complex part 18 Complex multiplication part 19 Inverse Fourier transform section 20 Display section

Claims (1)

[Claims] 1. Two receivers that receive spike signals emitted from sound sources located underwater; Two receivers that perform Fourier transform processing on corresponding received wave outputs of the two receivers;
two spectrum removal units that receive the outputs of corresponding ones of the two Fourier transform units and convert all spectra other than the frequency spectrum instructed from the outside or the frequency spectrum in the vicinity thereof to 0; a conjugate complex unit that generates a conjugate complex number of the output of one of the two spectrum removal units; a complex multiplication unit that calculates the product of the output of the other of the two spectrum removal units and the output of the conjugate complex unit; an inverse Fourier transform unit that performs inverse Fourier transform processing on the output of the complex multiplication unit;
a display unit that displays the output of the inverse Fourier transform unit;
An underwater acoustic signal detection device characterized by comprising: