JPH0371076B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an underwater noise generator used to generate broadband acoustic noise underwater for simulating radiated noise from a ship.

(Prior art) Conventionally, this type of noise generator needs to transmit a high signal level over a wide frequency band, so it uses multiple transmitters with different resonant frequencies, as shown in Fig. 3. A noise signal was transmitted using a circuit like the one shown. In the device shown in FIG. 3, a noise signal generated by one noise generator 11 is amplified by power amplifiers 21 to 23, and the noise is transmitted into the water in addition to transmitters 31 to 33 having different resonance frequencies. do.

(Problems to be Solved by the Invention) However, when transmitting waves using such a circuit, there are the following drawbacks. Each transmitter is designed to transmit nearly omnidirectional sound waves in its own frequency band. However, since they are driven by the same noise generator,
When measuring directivity by focusing on a narrow frequency band, the sound emitted from two sound sources constantly interferes to be in phase or out of phase in a specific direction determined by the distance between the sound sources and the wavelength, and the directivity changes. Sanya will be able to do it. In particular, in the frequency band near where the receiver switches, the two transmitters transmit sound at approximately the same level, resulting in large peaks and troughs. Fourth
The figure shows a directivity pattern cut by a plane including the straight line when multiple transmitters are arranged on a straight line and noise is transmitted using the conventional circuit configuration shown in Figure 3. Shows the results measured through a filter. If the frequency is constant, this directivity will not change even if measured multiple times, and the peaks and valleys in FIG. 4 will appear in a constant direction. The fact that there are peaks and valleys in the directivity means that sound waves in that frequency band are not transmitted in the direction of the valleys, and since the direction in which the peaks and valleys occur changes depending on the frequency, when observed from a specific direction, The sound pressure level varies depending on the frequency, which is extremely inconvenient when simulating ship radiation noise.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate such drawbacks and provide an underwater noise generator with less deviation in directivity over a wide frequency band.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the underwater noise generator provided by the present invention adds an uncorrelated noise signal to each of a plurality of transmitters and transmits the waves. It is characterized by

(Function) In the present invention, since a plurality of radiators transmit uncorrelated noise, it is possible to prevent peaks and valleys from constantly occurring in a specific direction due to interference of transmitted noise, and achieve directivity with little deviation. It is something.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of an underwater noise generator according to the present invention, and shows noise generators 11 to 11.
13, power amplifiers 21-23 and transmitters 31-
33. In this way, in this embodiment, each transmitter is driven by mutually independent and uncorrelated noise signals, and transmits sound into the water. Therefore, since there is no correlation between the sounds emitted from each transmitter, steady peaks and troughs in specific directions, which occur in conventional systems, do not occur in any frequency band. Therefore, even when focusing on a narrow frequency band, peaks and valleys in the directivity do not occur, and directivity with little deviation can be obtained. FIG. 2 is a directivity diagram measured under the same conditions as the measurement in FIG. 4 for this example. Measurements were made three times at the same frequency, and the directivity remained constant. As is clear from Figure 2,
The embodiment shown in FIG. 1 achieves directivity with less deviation than the conventional device shown in FIG. In addition, in Figure 2, there is a large valley on the left side, but this is caused by the jig that holds the transmitter for measuring directivity casting a shadow on the transmitted sound.
In this embodiment, a substantially omnidirectional radiation pattern is obtained.

(Effects of the Invention) As described above, the present invention can provide an underwater noise generator with little deviation in directivity over a wide frequency band.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Fig. 2 is a directivity pattern diagram of the embodiment, Fig. 3 is a block diagram showing a conventional underwater noise generator,
FIG. 4 is a directional pattern diagram of the underwater noise generator shown in FIG. 3. 11-13...Noise generator, 21-23...
Power amplifier, 31-33... Ultrasonic transmitter.

Claims (1)

[Claims] 1 Underwater noise generator used to generate broadband acoustic noise underwater for simulating radiated noise from ships, etc., which is composed of multiple transmitters with different resonance frequencies. means and
and noise generating means for applying uncorrelated noise signals to each of the plurality of transmitters to prevent interference between the transmitted wave outputs from the plurality of transmitters and generate a radiation pattern with little deviation from the transmitter. An underwater noise generator characterized in that it generates noise.