JPH04142485A - Underwater sound receiver - Google Patents

Abstract

PURPOSE:To sharply reduce the noise output voltage and largely improve the S/N ratio by floating the sensing section of a piezoelectric piece in a foam body and a filled acoustic medium. CONSTITUTION:A piezoelectric piece supporter is made of a punching metal. This case 9 is floated and supported in a boot 10 made of a bottomed and headed cylindrical body via a foam body 4. The vibration applied to the whole receiver is considerably attenuated by the foam body 4 but not to zero, it is transferred to a circular base 2 via a fitting screw 5, the noise output based on the vibration is generated at a sensing section. In case of the vertical vibration, distortions in opposite directions to each other are generated on piezoelectric pieces 1a, 1b, 3a, 3b centering on the circular base 2 via their masses, and outputs in opposite phases respectively are obtained. They are connected electrically in parallel or in series in a control circuit, the output voltage in opposite phases can be offset, and the effect of the noise output can be eliminated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention includes an electroacoustic transducer inside the boot, and transmits vibrations outside the boot to the electroacoustic transducer, converts it into an electrical signal, and outputs the signal. The invention relates to an underwater delivery device.

(Prior Art) When an underwater receiver is suspended from a platform hole to capture underwater sound waves, movement of the platform may cause the receiver to sway and generate acceleration noise. When this acceleration noise is generated, the acceleration noise is superimposed on the underwater sound wave received by the electroacoustic transducer, and the S/
This method has the disadvantage of reducing the N ratio (signal-to-noise ratio), which reduces the accuracy of measured values.

Generally, the noise output voltage in an underwater receiver is expressed as the sum of acoustic noise and acceleration noise. Here, acoustic noise level (N: μPa5), reception sensitivity (Mo: V/uPas
), acceleration (A:G=gravitational acceleration), acceleration sensitivity (Go
:V/G), the noise output voltage (Vn) is expressed by the following equation.

Vn= (N'0M.'+A'-G.・)A----
--" (1) +=u0(N"+A'(Go'Mo')
)' Also, the S/N ratio of the receiver output: (S/N)E is (S
/N)E =S-MO/MO(N'+A'%(Go' /MO2)) -----・----
−−−・−(3) is given.

(S/N)E can be improved by increasing the ratio between the acceleration sensitivity (GO) and the reception sensitivity (MO) in the denominator of equation (3).

(The problem to be solved by the invention! Therefore, two cylindrical piezoelectric elements are connected in tandem to each other via an annular pace as electroacoustic transducing elements, and the annular base is supported on a piezoelectric support in a boot. When vibrations from outside the boot are transmitted to the piezoelectric element via a liquid acoustic medium filled in the boot, at least the acceleration noise in the axial direction of the piezoelectric element is generated from the vibration of each piezoelectric element. The signal is offset to avoid a reduction in the signal-to-noise ratio.In this case, the pace has to be mechanically supported in the boot via a piezoelectric support, so that It is equipped with hanging supports.

However, when the pace is mechanically suspended in this way, vibrations are transmitted to the pace through the suspension struts, and the noise output based on the vibration is superimposed on the detection output, causing the S/
This results in a decrease in the N ratio.

(Object of the Invention) The present invention has been made based on the above circumstances, and as an electroacoustic transducer, in addition to the cylindrical piezoelectric element, a disc-shaped piezoelectric element attached to each terminal is prepared, and an annular piezoelectric element supporting these is prepared. When supporting the base on the piezoelectric support in the boot, make sure that mechanical vibrations from the boot are not directly transmitted to the piezoelectric support. The present invention aims to provide an underwater receiver that is devised to prevent the transmission of noise output due to vibrations.

(Means for Solving the Problem) Therefore, in the present invention, as clarified in the illustrated embodiment, two cylindrical piezoelectric elements (
la, lb), the piezoelectric elements (1a, 1b) being mounted at opposite ends thereof on an annular base (2), the annular base (2) being supported on a piezoelectric support in a boot (10); Each free end of the piezoelectric element (la, lb) has a disc-shaped piezoelectric element (
3a, 3b) to partition the internal space, and the piezoelectric support body is attached to the piezoelectric elements (la.

a cylindrical case (9) surrounding the cylindrical case (9), the case (9) being held within the boot (10) by a foam (4);
The case (9) and the boot (10) are configured to transmit vibrations outside the boot (lO) to the piezoelectric elements (la, 1b) (3a, 3b) using a liquid filled in the case (9) and the boot (10) as an acoustic medium. There is.

(Function) Therefore, the piezoelectric elements (la, lb) (3m, 3b)
The sensing part is floating on the foam (4) and the filled acoustic medium and does not come into direct contact with other solid objects, so it is free from the effects of vibrations that deteriorate its characteristics as an underwater receiver. broadband transmission sensitivity characteristics are maintained.

Furthermore, the foam (4) also has the effect of attenuating acceleration, so that the acceleration transmitted to the sensing section can be further reduced. As a result, combined with the mutual acceleration canceling effect of the cylindrical piezoelectric elements (la, lb), the acceleration output is significantly suppressed, and the disc-shaped piezoelectric element (3a).

By adding 3b), the receiving sensitivity improves, so S/
The N ratio can be increased.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to FIGS. 1 and 2. In the figure, numerals 1a and 1b are cylindrical piezoelectric elements employed as electroacoustic transducers, and the piezoelectric elements 1a and 1b are attached to an annular base 2 at one end facing each other. In addition, the piezoelectric elements 1a, l
At the other free end of b, disk-shaped piezoelectric elements 3a, 3b are attached, whereby the piezoelectric elements 1a, lb, 3a.

The space surrounded by 3b is sealed. A mounting screw 5 that also serves as a support bottle is screwed onto the outer periphery of the annular base 2, so that the pace 2 can be attached to the cylindrical case 9.
It is supported by a piezoelectric support consisting of.

In this embodiment, the piezoelectric support is made of punched metal. And this case 9
is supported in a suspended state via a foam 4 in a boot 10 which is a cylindrical body with a bottom and a head. Also,
An acoustic medium 11 such as a liquid such as silicone oil is filled in the boot 10 and the case 9 so as to be impregnated into the foam 4 .

In addition, in the figure, the code 8 is a metal plate provided on the top of the boot 10.
The conductive wire from the cable 13 that passes through the boot cap 12 and is connected to each piezoelectric element 1a in the case 9,
lb, 3a, and 3b are each equipped with watertight through-terminals 6 for electrically connecting via leait wires 7.

In such a configuration, the piezoelectric elements 1a, lb.

The sensing parts 3a and 3b are elastically supported by the foam 4 and floated in the filled acoustic medium 11, and the case 9 is not in direct contact with other solid objects, so it has characteristics as an underwater receiver. It is not affected by vibrations that worsen the transmission, and maintains a wide range of transmission sensitivity and frequency characteristics.

Furthermore, the foam 4 has the effect of attenuating acceleration, and the acceleration transmitted to the sensing portion is considerably reduced. Further, the output due to the acceleration is suppressed as follows. In other words, although the vibration applied to the entire receiver is considerably attenuated by the foam body 4, it does not become zero, so it is transmitted to the annular base 2 via the mounting screw 5, and the vibration is transmitted to the sensing part. However, in the case of vibration in the vertical direction, each piezoelectric element 1a around the annular base 2
, lb, 3a, and 3b generate distortions in opposite directions due to their own masses, and therefore, their respective outputs have opposite phases.

This can be canceled out as output voltages of opposite phases to each other by a control circuit that is electrically connected in parallel or in series, and the influence of noise output can be eliminated.

Therefore, the acceleration output is significantly suppressed compared to conventional underwater wave receivers due to the cancellation of the damping effect by the foam 4 and the acceleration output voltage of the sensing section.

In addition, by connecting four piezoelectric elements 1a, lb, 3m, and 3b in series, the receiving sensitivity (Mo) can be changed to MO: MO1+ MO
2+MO3+Mo4.For example, if the transfer sensitivity of each piezoelectric element is the same, a transfer sensitivity four times higher can be obtained.

Therefore, the acceleration output is suppressed and the transfer sensitivity is improved, so that the noise output voltage is significantly reduced. This allows the S/N to be significantly improved compared to conventional underwater receivers.

In the above embodiment, the cylindrical piezoelectric element 1a is used.

Although the disk-shaped piezoelectric elements 3a, 3b with straight planes are provided on 1b, the disk-shaped piezoelectric elements 3a, 3b with concave or convex planes may be used as shown in FIG. 3 or 4.

Further, a disk 14a is provided on the cylindrical piezoelectric elements 1a and lb.

14b may be attached, and the disc-shaped piezoelectric elements 3a, 3b may be attached thereto (see FIGS. 5 to 7). In this case, the piezoelectric elements 3a and 3b are attached to the disks 14m and 1
It is applied to both sides, inner or outer surface of 4b.

Furthermore, the piezoelectric elements 3a, 3b may be formed into semicircular shapes as shown in FIG. 8, and may be attached to the discs 14a, 14b.

(Effects of the Invention) The present invention has been detailed above, and the acceleration output is suppressed and the transfer sensitivity is improved, so the noise output voltage is reduced, the S/N ratio is improved, and even a weak signal sound can be achieved. Detection becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view showing one embodiment of the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIGS. 3 to 8 show modified examples of the piezoelectric assembly structure. FIG. la, lb-piezoelectric, 2-base, 3a, 3b-
Piezoelectric, 9-case, 10-boot, 4
-・Foam, 11-・Acoustic medium.

Claims (1)

[Claims] 1. Two cylindrical piezoelectric elements are provided as electroacoustic transducing elements, and the piezoelectric elements are attached to an annular base at one end facing each other,
The annular base is supported on a piezoelectric support in the booth, and a disc-shaped piezoelectric is attached to each free end of the piezoelectric to partition an internal space, and the piezoelectric support surrounds the piezoelectric. The device is configured to have a cage-shaped case, the case is held inside the boot with a foam, and vibrations outside the boot are transmitted to the piezoelectric element using a liquid filled in the case and the boot as an acoustic medium. This underwater receiver is characterized by: