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JPH0521595

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DESCRIPTION JPH0521595
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
underwater acoustic wave receiver, and more particularly to an underwater acoustic wave
receiver intended to be installed on a ship or the like.
[0002]
BACKGROUND OF THE INVENTION A conventional underwater acoustic wave receiver has a
structure molded with a synthetic resin 2c to maintain the watertightness of a piezoelectric
element 2a connected to a cable 2b, as shown in FIGS. 4 to 5. doing. In order to reduce acoustic
noise and vibration noise generated from the ship and to combine the receiving directivity, this
wave receiver combines an acoustic reflection material 2d such as sponge rubber with a metal
plate 2e that exerts an acoustic shielding effect on the upper surface of the acoustic reflection
material. Are attached to the baffle collectively molded with the synthetic resin 2c via the spacer
2f and then attached to the hull.
[0003]
In the conventional underwater acoustic wave receiver, it is possible to prevent the deterioration
of the wave receiving sensitivity in the low frequency region due to the acoustic reflection from
the baffle and to obtain the required wave receiving sensitivity. It was necessary to increase the
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distance between the acoustic receiver and the baffle. In addition, since the underwater acoustic
wave receiver is fixed to the baffle via the spacer 2f, there is a disadvantage that the supporting
area is small and the impact resistance is weak.
[0004]
SUMMARY OF THE INVENTION The present invention overcomes the disadvantages of the prior
art and, in particular, provides a durable underwater acoustic system capable of effectively
setting noise as well as setting a large mounting area on a ship. It aims at providing a wave
receiver.
[0005]
SUMMARY OF THE INVENTION In the present invention, a viscoelastic resin having a sound
velocity lower than that of seawater is disposed on one side of a piezoelectric element, and a
metal plate or the like is provided on the hull side of the viscoelastic resin. And the acoustic
reflection member such as sponge rubber are sequentially laminated, and the whole members
such as the piezoelectric element, the visco-elastic resin, the acoustic shielding member and the
acoustic reflection member are integrally molded with a synthetic resin. It has a composition of.
By this, it is intended to achieve the above-mentioned purpose.
[0006]
DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will
be described below with reference to FIGS. 1 and 2. FIG. In the embodiment shown in FIGS. 1 to
2, a visco-elastic resin 1f having a sound velocity slower than that of seawater is disposed on one
side of the piezoelectric element 1a, and a metal plate etc. is provided on the hull mounting side
of the visco-elastic resin The sound shielding member 1e and the sound reflecting member 1d
such as sponge rubber are sequentially laminated, and all members such as the piezoelectric
element 1a, the visco-elastic resin 1f, the sound shielding member 1e and the sound reflecting
member 1d are integrally synthesized. It is molded with resin 1c.
[0007]
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2
That is, the cable 1b is connected to the piezoelectric element 1a, and the visco-elastic resin 1f,
the metal plate 1e serving as the mass and the sponge rubber 1d are laminated under the
piezoelectric element 1a and molded with the synthetic resin 1c. It is a structure. In this
configuration, the receiving sensitivity can be expressed by the following equation in
consideration of the reflection from the sponge rubber having the effect of the baffle.
[0008]
Reception sensitivity Mv = 20 log (gh × t) -20 log ((1 + cos θ) 2+ (sin θ) 2) 1 /2
[0009]
Where θ = 180 + 720 f · l / c
[0010]
Further, gh: piezoelectric constant, t: piezoelectric element thickness, f: frequency, l: distance
between the piezoelectric element and the sponge rubber, c: sound speed between the
piezoelectric element and the sponge rubber.
[0011]
From the above equation, the first term is the wave receiving sensitivity of the piezoelectric
element alone, and the second term is the loss due to the reflected wave from the sponge rubber.
In order to make the second term smaller with the same dimensions as the conventional product,
c should be small, that is, a material having a slower sound velocity than seawater may be used
between the piezoelectric element and sponge rubber which were conventionally seawater.
Now, considering silicone gel as a viscoelastic resin and assuming l = 5 [cm,] c = 1000 [m / s], the
conventional product and the receiving sensitivity are as shown in Figure 3 and are the same as
the conventional product. Even the size can improve the reduction of the receiving sensitivity due
to the baffle.
[0012]
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Further, since the piezoelectric element and the sponge rubber are molded together, they have
the same vibration isolation, sound insulation effect and receiving directivity as the combination
of the conventional wave receiver and the baffle.
In addition, by using a visco-elastic resin between the piezoelectric element and the sponge
rubber to form an integral, solid structure and by supporting the entire surface of the receiver, it
is superior in impact resistance as compared with the conventional product. There is.
[0013]
Effect of the Invention In the present invention, by filling a viscoelastic resin having a sound
velocity lower than that of seawater between the piezoelectric element and the sponge rubber,
the time for the acoustic reflection from the sponge rubber to reach the receiver is delayed.
Therefore, it is possible to improve the reduction of the wave receiving sensitivity in the low
frequency region, and to provide a non-conventional practical underwater acoustic wave receiver
excellent in impact resistance.
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