JPS62231887A - Vibration proofing and sound proofing hull structure - Google Patents

Abstract

PURPOSE:To reduce underwater radiative noise from a hull in a special vessel equipped with an underwater sounder by providing a thin tank along the outer panel of the hull in place as required whereby filling liquid inside. CONSTITUTION:Both No.1 inner hull 1 and No.2 inner hull 2 are provided between a noise generator 6 and an outer panel 5 radiating noise into sea in such a way that the generator 6 is enclosed within the outer panel 5 to damp propagated sound whereby two layers of thin tanks 4 are formed into a U shaped cross section, and furthermore vertical and horizontal structural members such as a bulkhead and the like which connect spaces between inner hulls for filling liquid L such as water inside. Owing to this constitution, vibration radiated from the generator 6 is damped by interference between the liquid in the tank 4 and the structural member 1 through 3 and 5 for reducing underwater noise radiated from the outer panel 5 sharply. As a result, the measuring performance of an underwater sounder can be improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> This invention is applicable to special ships equipped with underwater acoustic equipment.
It relates to vibration-proof and sound-proof hull structures that are particularly effectively applied.

<Prior art and its problems> Currently, ships equipped with underwater acoustic equipment are equipped with various measures to reduce noise due to their functionality, but with the recent development of underwater acoustic equipment technology, Furthermore, the promotion of lower vocalization has become an important issue.

In other words, it is necessary to significantly reduce solid-borne sound that is generated inside the ship, propagates through the hull structure, and reaches underwater acoustic equipment, and underwater radiation noise emitted from the shell.

Conventional techniques for reducing underwater radiation noise from ships include (1) using vibration isolating materials in the frames of equipment that generates high-frequency vibrations, and (11) installing vibration absorbing materials that have a distributing effect on the inside of the ship's outer panels. (iii) The main method is to cover the hull above the waterline with bubbles generated from the hull shell.

However, the current situation is that even if these technologies are used in combination, they are still not sufficient as a measure against low-level underwater radiation noise.

This invention was proposed in view of the above circumstances, and its purpose is to reduce solid-borne sound propagating through the hull structure and to significantly reduce underwater radiation noise emitted from the exterior of the hull. The purpose of the present invention is to provide a vibration-proof and sound-proof hull structure that is highly reliable and maintainable.

Means for Solving the Problems> The vibration-proof and sound-proof hull structure according to the present invention includes a thin tank along the inside or outside of the hull skin in the noise generating equipment compartment and a part of the hull or the entire length of the hull. This thin tank has a layer or multiple layers and is filled with a liquid such as water, which attenuates solid-borne sound propagating through the ship's structural members due to interference between the liquid in the tank and the vibrations of the ship's structural members. ,
This is intended to significantly reduce underwater radiation noise emitted from the outside of the hull.

Furthermore, by arranging the vertical and horizontal structural members such as bulkheads of thin tanks and the vertical and horizontal structural members of adjacent thin tanks so that they are staggered rather than continuous, longitudinal waves and transverse shear waves of vibration components can be transmitted to the outer surface of the hull. The structure is such that it does not directly convert into bending waves, which is the sound generation mode, and aims to further reduce underwater radiation noise.

<Example> The present invention will be described below based on illustrated embodiments.

As shown in FIGS. 1 and 2, vibrations generated from the main engine and other vibration/noise generating equipment 6 propagate through the hull members via the pedestal 7, and the high frequency components are transmitted from the hull outer plate 5 into the water. The device 6 that is the source of the sound is emitted as sound.
In order to attenuate the propagated sound between the outer panel 5 and the outer panel 5 from which noise is radiated into the water, the present invention provides a first inner shell 1 and a second inner shell 1 to surround the equipment 6 inside the outer panel 5. An inner shell 2 is provided, a thin tank 4 having a substantially U-shaped cross section is formed in two layers, and vertical and horizontal structural members such as partition walls 3 are provided to connect the inner shells. Fill with liquid.

In such a configuration, the propagating vibrations are attenuated due to the interference between the liquid in the tank 4 and the vibrating structural members 1.2 and 3.5, and the underwater radiation noise radiated from the outer plate 5 is significantly reduced. be done.

Furthermore, it is known that when a structure contains a liquid, this liquid can significantly attenuate the energy of vibrations propagating through the structure at the joints of the structure.

Although FIGS. 1 and 2 show the case of two layers, the number of layers may be increased or decreased depending on the required reduction amount of underwater radiated sound, and may be a single layer or three or more layers.

Further, as shown in FIG. 3, the partition walls 3 and the like are not continuous in adjacent tanks 4, but are arranged in a staggered manner as shown in FIG. 4, and are structured not to penetrate the inner shell 1.2.

With such a structure, as shown in FIG. 5, the structure is such that the longitudinal waves 8 and transverse shear waves 9, which are vibration components, are not directly converted into bending waves 10, which are sound generation modes, in the hull outer plate 5. , underwater radiated sound is reduced.

Next, what is shown in FIGS. 6 and 7 is a two-layer thin tank 4 formed by a first outer shell 1' and a second outer shell 2' on the outside of the hull shell 5 and in a part of the hull. was formed. This ζ
Accordingly, it is possible to reduce underwater radiated noise in existing ships where underwater radiated noise is a problem without modifying the inside of the hull.

Next, an example of a vibration experiment using a model water tank as shown in FIG. 10 will be explained.

This experiment was conducted under the following conditions to investigate the effect of water on high-frequency vibrations transmitted through structures.

(1) A steel water tank as shown in FIG. 10 is made, and a steel plate P1 is vibrated by a vibrator installed at point A.

(ii) A random noise signal rectified to 1/6 octave width is input to the vibrator, and the center frequency is set to 'l KH2.
Change the frequency by 7 points up to 10KHz.

(++i) Measure the acceleration levels of steel plates P1 and P7 at each center frequency using an accelerometer.

(lv) The acceleration level of steel plates P1 and P7 is 10 on the steel plate.
It is determined by measuring at ~20 different positions and taking the average value.

Such an experiment was conducted with the tank empty and with the tank full of water, and the vibration energy of each steel plate was determined from the measured average acceleration level.

The measured value obtained by dividing the vibration energy of the steel plate P7 by the vibration energy of the steel plate P1 is shown in dβ in FIG. 11. This graph shows that when the water tank is filled with water, the vibration energy transmitted to the steel plate P7 is significantly reduced.

The above example shows the application to the reduction of underwater radiated sound of special ships, but this is not limited to this, and it is also possible to install a liquid tank between the noise source and the living area in structures such as ships and buildings. This can be applied to reducing noise levels in residential areas.

8 and 9 show an example in which the liquid tank 4 is provided between the living quarters 11 of the ship and the engine room 12 of the main engine 6. In this case, the tank is shaped along the inside of the upper deck 13 and the inside of the upper outer panel of the hull.

Also, install a liquid tank under the equipment that is the source of noise, or
By enclosing the equipment in a water jacket type liquid tank, it can be used as a countermeasure against equipment noise and noise.

Furthermore, in large structures including liquid tanks, such as chemical plants, by appropriately designing the shape and arrangement of the liquid tanks, the tanks can be used as vibration damping devices.

<Effects of the Invention> As mentioned above, according to this invention, the necessary parts of the hull are
A single layer or multiple layers of thin tanks are installed along the inside or outside of the hull shell, and these thin tanks are filled with liquid such as water.Furthermore, vertical and horizontal structural members such as bulkheads are staggered, so that the structure The structure takes into consideration the liquid effect on vibration energy and the conversion of vibration modes, making it possible to significantly reduce underwater radiation noise emitted from the hull compared to conventional models.

Furthermore, it utilizes vibrational interference between liquid and structural members.
Since it does not rely on special equipment, it is highly reliable and maintainable.

[Brief explanation of drawings]

Fig. 1 is a side view showing a hull according to the present invention, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, Fig. 3 is a schematic diagram showing an example of an inconvenient arrangement of bulkheads, and Fig. 4 is a main illustration of the present invention. A schematic diagram showing an example of the partition wall arrangement of the invention, FIG. 5 is a schematic perspective view showing vibration conversion, FIG. 6 is a side view showing the first modification, and FIG. 7 is a Vl-Vl diagram of FIG. 6.
8 is a side view showing the second modification, FIG. 9 is a sectional view taken along the line ■-■ in FIG. 8, FIG. 10 is a perspective view showing the model aquarium, and FIG. It is a graph of the experiment used. 1..First inner shell, 2..Second inner shell, 11..First outer thigh,
21. Second outer shell, 3. Bulkhead, 4. Tank, 5.
Outer plate, 6. Vibration/noise generating equipment, 7. Frame, 8.
Longitudinal waves, 9... Transverse shear waves, 10... Bending waves, 11... Living quarters, 12... Engine room, 13... Upper deck No. 10 rM

Claims (2)

[Claims] (1) A vibration-proof and sound-proof hull structure characterized by providing thin tanks along the outer skin of the hull at necessary locations on the hull, and filling the thin tanks with liquid. (2) The thin tank has multiple layers, and the structural members of the thin tank are not continuous with the structural members of the adjacent thin tank, but are offset from each other. Anti-vibration and soundproof hull structure.