JP2508261B2 - Underwater sound insulation - Google Patents

Description

TECHNICAL FIELD The present invention relates to an underwater sound insulation material, and more particularly to an underwater sound insulation material for underwater acoustic equipment, which has a wide sound insulation property and a high water pressure resistance.

[Conventional technology]

Conventionally, this type of sound insulation material has been made of rubber materials 11a, 11 as shown in FIG.
The air chamber 12 was created only by b, and the sound was insulated by the vibration and reflection of the air chamber caused by the underwater sound waves.

In this case, the effect of sound insulation is high especially at the frequency at which the air chamber resonates, so that the air chamber made of only rubber material has a low bulk modulus, and a sound insulating material suitable for low frequencies is secured even in a small air chamber. It was

However, since the air chamber is made of only rubber material, it cannot be used under high water pressure because the air chamber is crushed when hydrostatic pressure is applied and the sound insulation effect is lost.

In addition, in order to solve this problem, a flat air chamber 23 which is easy to bend is made of reinforced plastic 22 as shown in FIG.
There is a sound insulation material in which this is molded with a rubber material 21.

However, in this type of sound insulation material, since the elastic modulus of the air chamber is increased by the reinforced plastic, the resonance frequency of the air chamber is increased, and the sound insulation effect is remarkably reduced at a low frequency below the resonance frequency.

Further, if the flat surface of the reinforced plastic is widened to lower the resonance frequency and the elastic modulus of the air chamber is lowered, the strength is lowered and the water pressure resistance is lowered.

[Problems to be Solved by the Invention]

The above-mentioned conventional underwater sound insulation material is suitable for low frequency when the air chamber is made of only rubber material, but has low water pressure resistance, and low frequency when the air chamber is made of flat reinforced plastic. However, there is a drawback in that the water pressure resistance is lowered when it is made to be high, and the low frequency sound insulation effect is remarkably lowered when the water pressure resistance is increased.

In order to solve the above-mentioned drawbacks, the object of the present invention is not limited to one type of material for forming the air chamber, but the wall member constituting the air chamber is divided into two types to reduce the low elastic modulus of the air chamber. An object of the present invention is to provide an underwater sound insulation material which is improved in strength against hydrostatic pressure load while being maintained.

[Means for solving the problem]

The underwater sound insulation material of the present invention is a rubber plate having a thickness corresponding to the sound insulation frequency, and through holes having a diameter corresponding to the sound insulation frequency, which are evenly arranged, and fitted into both ends of the through hole. An underwater sound insulation plate having a disk that forms an air chamber that resonates at a sound insulation frequency and that performs a predetermined flexural resonance, and a rubber plate and a sheath that hermetically covers the outer surface of the disk is provided. Moreover, it is comprised by laminating | stacking the said several underwater sound-insulating board formed according to the sound-insulating frequency band.

〔Example〕

Next, the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an embodiment of the present invention, showing an example of an underwater sound insulation material formed by laminating underwater sound insulation plates for three frequency bands of low, middle and high.

The configuration of the embodiment shown in FIG. 1 is the underwater sound insulation board for the low frequency band.
100, an underwater sound insulation plate 200 for the middle frequency band and an underwater sound insulation plate 300 for the high frequency band.

The low frequency band underwater sound insulating plate 100 of the first layer has a disk (1) 2a made of synthetic resin or metal with large vibration damping in the counterbore 5a at both ends of the through hole provided in the rubber plate (1) 1a. By embedding, the air chamber (1) 3a is formed, and the rubber plate (1) is formed.
Outer outer surfaces of 1a and the disc (1) 2a are covered with a sheath (1) 4a and a sheath (2) 4b.

The underwater sound insulation plate 200 for the middle frequency band of the second layer is provided with a through hole having a diameter smaller than that of the first layer in the rubber plate (2) 1b thinner than the first layer, and the counterbore portions 5b are provided at both ends of the through hole. And a disk (2) 2b having a diameter smaller than that of the first layer is embedded in both counterbore portions to form an air chamber (2) 3b, and outer surfaces thereof are sheath (2) 4b and sheath (3) 4c. It is covered with and.

The high frequency band underwater sound insulation plate 300 of the third layer includes a rubber plate (3) 1c thinner than the second layer, a through hole having a diameter smaller than that of the second layer, and a disk (3) 2c. 3) 3c is formed, and the outer surface is covered with the sheath (3) 4c and the sheath (4) 4d.

Next, the operation of this embodiment will be described. Prior to the detailed description of the embodiment of FIG. 1, the basic features of the present invention will be described.

The first feature of the present invention is that the through holes are evenly distributed in the rubber plate, the air chambers are formed by fitting the disks at both ends of the through holes, and the air chambers are resonated at the sound insulation frequency. In addition, while the outer surface is closely covered with a sheath, a low elastic modulus is maintained by the rubber plate that supports both discs and the air chamber to ensure the sound insulation effect at low frequencies, and the flexural strength of both discs and It is to secure high water resistance by the strength of the rubber plate biting between both discs.

A second feature of the present invention is that the discs fitted to both ends of the through hole are made of synthetic resin or metal with large vibration damping to dampen the flexural resonance of the discs to broaden the sound insulation frequency characteristic. Especially.

A third feature of the present invention is that a plurality of types of underwater sound insulation plates having different sizes of an air chamber, vibration characteristics of a disk, and the like are laminated, so that the sound insulation frequency can be broadened. The embodiment of FIG. 3 shows a case where three types of underwater sound insulation plates of low, middle and high are laminated to widen the sound insulation frequency band.

 Returning to FIG. 1 again, the description of the embodiment will be continued.

Assuming that the mass of each disk in the underwater sound insulation plate for each of the low, middle, and high frequency bands described above is m1, m2, and m3 in the low to high frequency band direction, respectively, these masses m1 to m3 and the corresponding air chambers Rubber plates (1) 1a, (2) 1b and (3) 1c
Spring constant k of each of the spot facings 5a, 5b and 5c of
1, k2 and k3 form a resonance system of longitudinal vibration shown in FIG. 2 (a), and the air chamber (1) 3a, air chamber (2) 3b and air chamber (3) 3c are formed at and near the resonance frequency. The absorption of the vibration of this vibration system is performed, and the penetration of the sound wave in the frequency band centered on the resonance frequency and the frequency in the vicinity thereof is blocked.

FIG. 2B is a sectional view for explaining the flexural vibration of the discs (1) 2a to (3) 2c.
(3) As indicated by the dotted line, 2c causes flexural vibration in the upward and downward directions by repeating the resonance frequency.

This longitudinal vibration resonance system resonates at a lower frequency as the mass of the disc becomes larger and the spring constant of the spot facing part becomes smaller. It becomes a sound insulation material.

Furthermore, the discs of each layer have a resonance system due to flexural vibration as shown in Fig. 2 (b), which is determined by the elastic constant, specific gravity, diameter, and plate thickness of each material. Like the resonance frequency of vibration, the sound wave is blocked by absorbing the vibration into the air chamber.

This flexural resonance frequency becomes higher than the resonance frequency of longitudinal vibration mainly due to the difference between the flexural spring constant of the disc and the longitudinal vibration spring constant of the spot facing portion of the rubber plate.

Also, at a diameter / thickness ratio where the flexural strength of the discs of each layer is constant, the flexural resonance frequency becomes lower as the disc diameter becomes larger, and the sharpness of resonance is the magnitude of vibration damping, that is, mainly the spring constant. Depends on the size of the loss. Generally, the loss of the spring constant of the rubber plate is large,
The resonance characteristic of longitudinal vibration becomes dull, and the frequency characteristic of sound insulation becomes wide band.

When a general elastic material is used, the flexural resonance of the disk is sharp and narrow because the loss of the spring constant of the flexure is small. By using a disk made of a material having a large spring constant loss, that is, a material having a large vibration damping, such as a resin or a vibration-proof metal, it is possible to slow down the resonance and widen the frequency characteristic of sound insulation.

As described above, the mass of the disc, that is, the material, the outer diameter, and the thickness, and the spring constant of the rubber plate, that is, the material and the thickness of the rubber plate and the supporting area of the disc of the counterbore are adjusted for each layer. , Longitudinal vibration resonance frequency of counterbore of disk and rubber plate
By uniformly setting f _l1 , f _l2 , f _l3 and the flexural resonance frequencies f _B1 , f _B2 , f _B3 of the disk, a broadband sound insulation characteristic as shown in FIG. 3 can be obtained.

Fig. 3 shows the sound pressure transmittance of the rubber plate shown by the solid line, and the longitudinal vibration resonance frequencies f _l1 , f _l2 , f _{l3 by the} three types of discs and the _counterbore and the flexural resonance frequencies of the three types of discs. The sound pressure transmissivity having a downward single-peak characteristic shown by and the characteristics relating to the comprehensive sound pressure transmissivity of a wide band shown by a solid line in which the above sound pressure transmissivities are integrated are shown.

Now, the water pressure resistance of the longitudinal vibration resonance system in such a structure depends on the flexural strength of the disc and the strength of the air chamber,
Therefore, it is determined by the biting strength of the rubber wall around the air chamber into the air chamber due to the water pressure. The biting pressure to such an air chamber is brought about by the water pressure, and therefore has the same value as the water pressure, while the supporting force of the disc against the air chamber and the rubber wall surrounding the air chamber is the contact between the disc and the counterbore. As the applied water pressure increases in proportion to the ratio of the area of the disk to the area, the amount of penetration of the rubber wall into the air chamber is suppressed, the strength against the penetration of the air chamber is increased, and the water pressure resistance is enhanced. It

The above-mentioned enhancement of water pressure resistance will be described in more detail below.

FIG. 4 is a cross-sectional view for explaining the water pressure resistance of the air chamber in the embodiment of FIG.

FIG. 4 shows, as an example, the case of an air chamber (1) 3a formed by a disc (1) 2a and a rubber plate (1) 1a.

In Figure 4, the pressure P _b biting air chamber walls to air chamber wall W of the air chamber (1) 3a are those provided by the water pressure P _O, therefore P _b = P _O.

Now, assuming that the diameter of the disc (1) 2a is 2A and the diameter of the air chamber (1) 3a is 2B, the air generated by the pair of opposing discs (1) 2a in the Z-axis direction by the rubber plate (1) 1a. The indoor wall support pressure P _S is expressed by the following equation (1).

For example, when set to B / A = 3/4 P S = 2.3P b, the B / A 1/2
When set to, P _S = 1.3P _b , which is the air chamber (1) 3
The water pressure resistance of a is enhanced.

The basis of formula (1) is based on the following contents. That is, the external force F _O caused by the water pressure P _O in the Z-axis direction of the disc (1) 2a is F _O = P _O × πA ² , and the Z of the disc (1) 2a is
The relationship between the supporting pressure P _S and the supporting force F _S by the rubber plate (1) 1a in the axial direction is expressed by the following equation (2).

F _S = P _S × π (A ² −B ² ) ... (2) F _O = F _S due to the balance between the external support pressure P _S and the supporting force, so P _O × π A ² = P _S × π (A ² −B ² ) is obtained, from which Eq. (1) is derived. That is, P _S > P _b .

In this way, it is possible to realize an underwater sound insulation material in which the widening of the sound insulation frequency and the enhancement of the water pressure resistance coexist.

The above-described embodiment is an example in which three underwater sound insulation plates for low, middle and high frequency bands are layered to form a wideband underwater sound insulation material, but these are separately used according to the purpose of sound insulation. Of course, it is also possible.

In addition, the disk forming the air chamber together with the rubber plate can be used in the same manner as a disk in which the deformation is raised from the peripheral portion of the disk toward the center to equalize vibration fatigue. Obviously, any of the above modifications can be easily implemented without impairing the gist of the present invention.

〔The invention's effect〕

As described above, the present invention forms the air chamber by fitting the disks at both ends of the through holes evenly arranged in the rubber plate,
By making this air chamber resonate at a sound insulation frequency, it is possible to block underwater sound waves in a low frequency band with high water pressure resistance.

In addition, the sound insulation frequency characteristic due to flexural resonance can be broadened by selecting the material of the disc. Furthermore, by stacking a plurality of types of underwater sound insulation plates having different sound insulation characteristics, it is possible to achieve a wide sound insulation frequency band.

[Brief description of drawings]

1 is a perspective view of an embodiment of the present invention, FIG. 2 (a) is an explanatory view of a vibration system formed in the embodiment of FIG. 1, and FIG.
(B) is an explanatory view of the flexural vibration of the cylindrical plate in the embodiment of FIG. 1, FIG. 3 is a frequency characteristic diagram of sound pressure transmittance in the embodiment of FIG. 1, and FIG. 4 is an implementation of FIG. A cross-sectional view for explaining the water pressure resistance of an example air chamber, FIG. 5 and FIG. 6 are perspective views of a conventional underwater sound insulation material, respectively. 1a, 1b, 1c ... Rubber plates (1) to (3), 2a, 2b, 2c ... Discs (1) to (3), 3a, 3b, 3c ... Air chambers (1) to (3) ,
4a, 4b, 4c, 4d …… Sheaths (1) to (4), 5a to 5c …… Spot facing, 11a, 11b …… Rubber material, 12 …… Air chamber, 21 …… Rubber mold, 22 …… Reinforced plastic, 23 ... air chamber,
100 …… Underwater sound insulation board for low frequency band, 200 …… Underwater sound insulation board for medium frequency band, 300 …… Underwater sound insulation board for high frequency band.

Claims (2)

(57) [Claims] 1. A rubber plate having a thickness corresponding to a sound insulation frequency and having through holes of a diameter corresponding to the sound insulation frequency evenly arranged, and a rubber plate fitted at both ends of the through hole to obtain the sound insulation frequency. An underwater sound insulation material, comprising an underwater sound insulation plate having a disk that forms a resonating air chamber and that performs a predetermined flexural resonance, and a rubber plate and a sheath that hermetically covers the outer surface of the disk. . 2. The underwater sound insulation material according to claim 1, wherein a plurality of the underwater sound insulation plates formed according to a sound insulation frequency band are laminated.