JPH11215583A - Sonar system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a system to produce a sound signal of a vessel-mount type hydrophone whose frequency versus reception sensitivity characteristics is corrected. SOLUTION: A sound signal S0 propagating in water is attenuated, depending on an underwater propagation frequency characteristics and the resulting signal reaches a vessel-mount type hydrophone 31. A filter 32 corrects a reception signal S31 outputted from the hydrophone 31 to obtain a correction signal S32, in which the underwater propagation frequency characteristics is corrected. A phase alignment device 33 generates a sound signal S33. Since the hydrophone 31 has a specific frequency versus reception sensitivity characteristics, the effect remains in the sound signal S33. A frequency characteristics correction filter 34 eliminates the effect of the frequency versus reception sensitivity characteristics of the hydrophone 31 remaining in the sound signal S33. A hydrophone 21 is not of a vessel-mount type and installed in an exclusive installation location of a ship such as a bow of a ship. An equalizer(EQL) 22, that corrects a received signal S21 to produce a correction signal S22, is connected to an output of the hydrophone 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sonar system for receiving an acoustic signal with a hydrophone and acquiring information on the underwater such as underwater.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a receiving section of a conventional sonar system, and FIGS. 3A to 3D are frequency characteristic diagrams of signals S0 to S3 in FIG. The receiver of this sonar system includes a hydrophone 1 that receives and outputs an acoustic signal S0 propagating in the sea, an equalizer (EQL) 2 connected to the hydrophone 1, and a phasing connected to the equalizer 2. Vessel 3. Conventionally, there was no type of hydrophone directly attached to a hull such as a hull, so the hydrophone 1 in FIG.
It is located in its dedicated place.

[0003] As shown in FIG.
It propagates in the sea with a frequency characteristic of 6 dB / oct. The hydrophone 1 that has received the acoustic signal S0 outputs a received signal S1 having the same frequency characteristics as the acoustic signal S0 as shown in FIG. The equalizer 2 has a 6 dB /
oct, and corrects the received signal S1. As a result of this correction, as shown in FIG. 3C, a correction signal S2 whose level is flat with respect to the frequency is obtained. The phase adjuster 3
The phasing is performed on the correction signal S2, and the audible sound signal S3 having a flat frequency versus level characteristic is output to an analysis unit (not shown) at the subsequent stage.

[0004]

However, the conventional sonar system has the following problems. recent years,
A hull-mounted hydrophone 11 that can be directly attached to a hull without providing a dedicated place on a ship such as a ship has been developed. For this reason, it is not necessary to add a dedicated place, and the receiving unit shown in FIG. 2 using the hydrophone 1 and the receiving unit using the hull mounted hydrophone 11, for example, have been used in combination. FIG. 4 is a configuration diagram showing a receiving unit using a conventional hull mounted hydrophone, and FIG.
6 is a frequency characteristic diagram of signals S11 to S13 in FIG.

This receiving unit is used in combination with the receiving unit shown in FIG. 2, and includes a hull-mounted hydrophone 11 for receiving an acoustic signal S0, an equalizer 12 connected to the hull-mounted hydrophone 11, A phase adjuster 13 connected to the equalizer 12. The sound signal S0 is shown in FIG.
As in (a), the hydrophone 11 propagates in the sea with a frequency characteristic of -6 dB / oct, but receives the acoustic signal S0.
Is different from that of the hydrophone 1.
That is, the reception sensitivity in the low frequency region is deteriorated, and the frequency characteristic of the reception signal S11 output from the hydrophone 11 is distorted as shown in FIG. The equalizer 12 converts the received signal S11 into 6 dB / oc, which is opposite to the sound signal S0.
t is corrected, and a correction signal S12 is output. Even if this correction is performed, the frequency characteristic of the correction signal S12 does not become flat as shown in FIG. Therefore, the level of the audible sound signal S13 output from the phasing device 13 that performs phasing to the correction signal S12 to the subsequent analysis unit also changes as shown in FIG.
The sound signal S3 shown in FIG.
And different. Therefore, the processing in the subsequent analysis unit
There have been adverse effects such as the necessity of being distinguished from the hydrophone 1 or 11.

[0006]

In order to solve the above problems, the present invention is directed to a hydrophone which is directly attached to a hull, receives a sound signal propagated in water, and outputs a received signal, An equalizer that performs correction on the reception signal output by the hydrophone with a frequency characteristic opposite to the frequency characteristic of the propagation of the acoustic signal, and outputs a correction signal, and performs phasing on the correction signal to obtain a audible sound signal. And a phase adjuster that generates underwater information, and obtains underwater information from the audio signal. The sonar system has the following configuration. That is, there is provided a filter which is connected to the output side of the equalizer or the phase adjuster and removes the influence of the frequency-sensitivity characteristic in the reception of the hydrophone on the correction signal or the audible sound signal and corrects the signal.

According to the present invention, as described above, the sonar system is configured, so that the reception signal output from the hydrophone directly attached to the hull is corrected by the equalizer, and the phasing by the phasing device is converted to the zero signal. Become. Here, the received signal includes a frequency-sensitivity characteristic 0 in hydrophone reception.
Since the influence is included, the correction signal and the sound signal output from the equalizer also have the influence. The effect of the frequency-sensitivity characteristic on the reception of the hydrophone is removed by the filter, and the correction signal or the audible sound signal is corrected. Therefore, the above problem can be solved.

[0008]

FIG. 1 is a block diagram showing a main part of a sonar system showing an embodiment of the present invention. This sonar system includes two systems of receiving units 20 and 30 and the receiving units 2 and 30.
And a selector 40 connected to outputs 0 and 30. The receiving unit 20 includes a hydrophone 21 that receives an acoustic signal S0 that has propagated in water such as the sea and outputs a received signal S21. The hydrophone 21 is not a hull mounted type, but is disposed at a dedicated installation place provided at, for example, a bow of a ship such as a ship. On the output side of the hydrophone 21, a correction is performed on the reception signal S21 to generate a correction signal S.
An equalizer (EQL) 22 for generating an E.22 is connected. A phase adjuster 23 that adjusts the phase of the correction signal S22 to generate a sound signal S23 is connected to the output side of the equalizer 22.

The receiving section 30 has a hull mounted hydrophone 31 that receives the acoustic signal S0 and outputs a received signal S31. The hydrophone 31 is added to the hydrophone 21 at the bow, and is directly attached to, for example, a stern hull. An equalizer 32 that corrects the received signal S31 and generates a correction signal S32 is connected to the output side of the hydrophone 31. Equalizer 3
2, the correction signal S32 is phased and the sound signal S3 is output.
3 is connected, and a frequency characteristic correction filter 34 is connected to the output side of the phase adjuster 33. The output terminal of the frequency characteristic correction filter 34 of the receiving unit 30 and the output terminal of the phase adjuster 23 of the receiving unit 20 are connected to the selector 40. The selector 40 selects an output signal of the frequency characteristic correction filter 34 or an output signal of the phase adjuster 23, and outputs the selected signal as an audio signal S40 to a subsequent analysis unit (not shown).

FIG. 6 is a circuit diagram showing a configuration example of the frequency characteristic correction filter 34 in FIG. The frequency characteristic correction filter 34 corrects the audible sound signal S33 by removing the influence of the frequency-sensitivity characteristic at the reception of the hull-mounted hydrophone 31, and is constituted by, for example, an active filter. The input terminal In of the frequency characteristic correction filter 34 is connected to the inverting input terminal (-) of the operational amplifier 34b via the resistor 34a. Operational amplifier 34b
, A power supply voltage of 15 V is applied via a resistor 34c, and a power supply voltage of -15V is applied via a resistor 34d. The non-inverting input terminal (+) of the operational amplifier 34b is grounded via an offset compensating resistor 34e. The output terminal of the operational amplifier 34b is connected to the output terminal Out of the frequency characteristic correction filter 34, and is connected to one end of the resistor 34f and one end of the resistor 34g. The other end of the resistor 34f is directly feedback-connected to the inverting input terminal (-) of the operational amplifier 34b, and the other end of the resistor 34g is feedback-connected to the inverting input terminal (-) via the capacitor 34h.

FIG. 7 shows signals S0, S21 to S3 in FIG.
FIG. 8 is an explanatory diagram of the frequency characteristic of FIG. 4, and the operation of the sonar system of FIG. 1 will be described with reference to FIG. The acoustic signal S0 propagates in the water such as the sea, and
1 but its frequency to level relationship is -6 dB
/ Oct. The hydrophone 21 outputs a reception signal S21 having the same frequency-to-level relationship as the acoustic signal S0, and supplies it to the equalizer 22. The equalizer 22 has a frequency of 6 dB / o, which is opposite to the frequency characteristic of underwater propagation.
ct, the received signal S21 is corrected with the correction signal S
22 is generated. The frequency-to-level relationship in the correction signal S22 becomes flat due to the correction. The phase adjuster 23 phase-corrects the correction signal S22 to generate a sound signal S23. The relationship between the frequency and the level of the sound signal 23 becomes flat similarly to the correction signal S22.

On the other hand, the hull-mounted hydrophone 31 has a frequency-to-reception sensitivity characteristic different from that of the hydrophone 21 due to reflection and absorption of the acoustic signal S0, and deteriorates in a low frequency region. Therefore, the reception signal S output by the hydrophone 31
In the frequency-to-level characteristic of 31, the level at the low frequency is low as shown in FIG. The equalizer 32 provides the received signal S31 with a frequency characteristic that is opposite to the frequency characteristic of undersea propagation.
The correction is performed with the characteristic of dB / oct to generate the correction signal S32, and the phase adjuster 33 performs the phasing on the correction signal S32 to generate the audio signal S33. The frequency-level relationship in the correction signal S32 or the listening signal S33 is such that the level at low frequencies is low due to the reception sensitivity of the hydrophone 31. Here, considering the case where the hearing sound signal S33 is directly input to the selector 40,
Has a different frequency-to-level relationship from the listening sound signal S23.
This is inconvenient because 40 is provided at a later stage. Therefore, the sound signal S is passed through the frequency characteristic correction filter 34.
33 is corrected.

The frequency characteristic correction filter 34 converts the audio signal S33 input from the input terminal In into an operational amplifier 34b.
Amplify using At the inverting input terminal (-) of the operational amplifier 34b, a negative feedback rope is formed from an output terminal composed of a resistor 34f and a resistor 34g and a capacitor 34h. Capacitor 34h increases the impedance in the negative feedback loop at low frequencies, thus reducing the negative feedback voltage at low frequencies. Therefore, the frequency characteristic correction filter 34 is a low-pass filter having a transfer characteristic opposite to the frequency-to-level relationship in the audio signal S33, and removes and corrects the influence of the frequency-sensitivity characteristic of the hydrophone 31 in the audio signal S33. Will do.
With this correction, a sound signal S34 having a flat frequency-level relationship is generated and provided to the selector 40 via the output terminal Out. The selector 40 detects the sound signal S2
3 or S34 is selected based on a selection signal or the like, and is provided to a subsequent analysis unit (not shown).

As described above, according to the present embodiment, the receiving unit 30 including the hull-mounted hydrophone 31, the equalizer 32, and the phase adjuster 33 is provided with the frequency characteristic constituted by the active filter using the operational amplifier 34b. Correction filter 34
Is provided, even if the characteristic of the frequency versus reception sensitivity of the hydrophone 31 deteriorates in the low frequency region and the sound signal S33 is still affected, the influence can be removed. Therefore, the receiving unit 20
The characteristics of the sound signal S23 obtained in the above step become the same as the sound signal S34 output from the frequency characteristic correction filter 34,
Even if the signals S23 and S34 are switched and applied to the subsequent stage, there is no need to distinguish the processing at the subsequent stage.

Note that the present invention is not limited to the above embodiment, and various modifications are possible. For example, there are the following modifications. (1) In the above embodiment, the frequency characteristic correction filter 3
4 shows an example in which it is connected to the output side of the phase adjuster 33, the same effect can be obtained even if it is connected to the output side of the equalizer 32. (2) The frequency characteristic correction filter 34 can have a configuration other than that shown in FIG. 6, and can be, for example, a bandpass filter that matches the reception sensitivity of the hydrophone 31. (3) The frequency characteristic correction filter 34 outputs the sound signal S3
When 3 is not an analog signal but a digital signal, a digital filter is used instead of an active filter.

[0016]

As described above in detail, according to the present invention, a sonar system having a hydrophone, an equalizer, and a phase adjuster directly mounted on a hull is provided with a filter at an output side of the equalizer or the phase adjuster. Is connected, it is possible to generate a sound signal in which the influence of the frequency-sensitivity characteristic on the reception of the hydrophone is removed. Therefore, for example, even when used in combination with a type of hydrophone that cannot be directly attached to the hull, there is no need to separately perform processing on the audio signal.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a main part of a sonar system according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a receiving unit of a conventional sonar system.

FIG. 3 is a frequency characteristic diagram of signals S0 to S3 in FIG. 2; .

FIG. 4 is a configuration diagram showing a receiving unit using a conventional hull mounted hydrophone.

FIG. 5 is a frequency characteristic diagram of signals S11 to S13 in FIG.

FIG. 6 is a circuit diagram showing a configuration example of a frequency characteristic correction filter in FIG. 1;

FIG. 7 is an explanatory diagram of frequency characteristics of signals S0, S21 to S34 in FIG.

[Explanation of symbols]

 20, 30 Receiving unit 21 Hydrophone 31 Hull mounted hydrophone 22, 32 Equalizer 23, 33 Phase adjuster 34 Frequency characteristic correction filter 40 Selector S0 Acoustic signal S21, S31 Received signal S22, S32 Corrected signal S23, S33 Hearing signal

Claims (1)

[Claims] 1. A hydrophone directly attached to a hull for receiving an acoustic signal propagated in water and outputting a received signal; and a hydrophone having a frequency characteristic opposite to that of propagation of the acoustic signal in the water. An equalizer that corrects the received signal output by the phone, and outputs a correction signal, and a phase adjuster that performs phasing on the correction signal to generate a audible sound signal. In a sonar system that acquires information, the sonar system is connected to an output side of the equalizer or the phase adjuster,
A sonar system, comprising: a filter that removes an influence of a frequency-sensitivity characteristic upon reception of the hydrophone and corrects the correction signal or the audio signal.