JP2022053810A - Underwater noise reflection absorption structure, underwater noise reducing structure, and underwater noise reducing method - Google Patents

Abstract

To provide an underwater noise reflection absorption structure that can efficiently reduce underwater noise generated by a construction such as pile installation, and an underwater noise reducing structure and an underwater noise reducing method through use of the same.SOLUTION: An underwater noise reflection absorption structure 1 is configured to, in order to reduce underwater noise, reflect underwater noise by a sound entering surface 1c, and absorb or reflect underwater noise or resonate with underwater noise within the underwater noise reflection absorption structure 1.SELECTED DRAWING: Figure 1

Description

The present invention relates to an underwater noise reflection absorption structure that suppresses underwater noise, an underwater noise suppression structure using the structure, and an underwater noise suppression method.

There is concern that noise from pile driving in water will propagate to the surrounding area and affect marine life. Generally, sound is attenuated by obstacles such as buildings and structures, but in water where there are no obstacles in the vicinity, the generated sound tends to spread over a wide area. Regarding underwater noise, frequencies and the like that affect dolphins, whales, fish, etc. have been reported (Non-Patent Document 1). In addition, it has been clarified that fish have a level of damage (220 dB or more), a threatening level indicating abusive behavior (140 to 160 dB), etc., and that underwater noise is attenuated with distance (non-patent documents). 2).

As a method for mitigating the effects on fish and marine mammals, "underwater noise reduction device and deployment system" (Patent Document 1), "air bubble curtain" (for example, Patent Document 2), and "pile sleeve" (non-patent document). 3) etc.

Japanese Unexamined Patent Publication No. 2017-504844 Jitsukaihei 1-119431 Gazette

Tomonari Akamatsu, Riko Kimura, Kotaro Ichikawa "Underwater Bioacoustics-Voice-Exploring Behavior and Ecology" Corona Publishing Co., Ltd. (2019) "Port Construction Environmental Conservation Technology Manual Doctor of the Sea (Revised 3rd Edition)" Japan Dredging and Reclamation Association (2015) "Implantation type offshore wind power generation introduction guidebook (final version)" New Energy and Industrial Technology Development Organization (March 2018) https://www.nedo.go.jp/news/press/AA5_101085 .html

The air bubble curtain of Patent Document 2 is effective as a method for alleviating underwater noise at the time of pile driving, but requires a dedicated ship or equipment for laying an air supply pipe and providing air. Air bubble curtains are widely used in Europe and the like to mitigate the effects on marine mammals such as dolphin whales.

In addition, it is assumed that Japanese offshore wind power generation facilities will be installed at a depth of 20 to 30 m (in Europe, they are often installed at a depth of about 10 m), but as the water depth increases, the efficiency of air bubble curtains will decrease. Conceivable. Boyle's law pV = constant (the product of volume V and pressure p is constant at a constant temperature), and when the pressure increases to 2 atm at a depth of 10 m, 3 atm at 20 m, and 4 atm at 30 m, the volume becomes 1 /. This is because the volume of gas, which is effective for sound absorption, decreases as the water depth increases to 2, 1/3, and 1/4.

In view of the above-mentioned problems of the prior art, the present invention relates to an underwater noise reflection absorption structure capable of efficiently suppressing underwater noise generated by construction such as pile driving, an underwater noise suppression structure using the same, and an underwater noise suppression structure. It is an object of the present invention to provide a method for suppressing underwater noise.

The underwater noise reflection / absorption structure for achieving the above object is an underwater noise reflection / absorption structure for suppressing underwater noise, which reflects underwater noise on a sound incident surface and is the underwater noise reflection / absorption structure. It is configured to absorb or reflect noise internally or resonate with noise.

According to this underwater noise reflection absorption structure, when installed underwater, underwater noise is reflected on the sound incident surface, and at the same time, it is absorbed, reflected, and resonated inside the underwater noise reflection absorption structure, thereby driving a pile. Underwater noise generated by construction work such as installation can be efficiently suppressed.

In the underwater noise reflection absorption structure, it is preferable that the shape of the sound incident surface is a curved surface or an inclined surface. As a result, underwater noise incident on the sound incident surface can be efficiently reflected. The curved surface includes a circular shape, an oval shape, and the like. The inclined surface shape is a surface inclined with respect to the horizontal direction, and may include a plurality of surfaces having different inclination directions.

Underwater noise can be reduced internally by including a filling material composed of at least one of a gas, a liquid having a specific gravity higher than that of water, a sound absorbing material, a reflective material, and a resonant material. The filling material is preferably a gas, a gas and a sound absorbing material, a gas and a reflective material, a gas and a resonant material, or a resonant material.

An outer shell body that constitutes the sound incident surface and has an internal cavity can be provided, and the filling material can be filled in the internal cavity.

The outer shell body may be divided, the inner cavity of each divided outer shell body may be filled with a filling material, and the divided outer shell bodies may be integrated. It's okay.

The underwater noise reflection absorption structure can be configured to have a columnar shape as a whole, and may be, for example, a triangular prism, a square column, a column, a semi-cylindrical column, or the like.

Further, the underwater noise reflection absorption structure may be entirely formed in a plate shape, and in this case, the sound incident surface may be formed in a wavy shape or a triangular shape or a sawtooth shape. Preferably, underwater noise can be efficiently reflected on such an uneven surface.

The underwater noise suppression structure for achieving the above object is an underwater noise suppression structure including the above-mentioned underwater noise reflection absorption structure.

According to this underwater noise suppression structure, an underwater noise reflection absorption structure capable of efficiently suppressing underwater noise is included, and underwater noise can be efficiently suppressed and diffusion of underwater noise can be suppressed.

Another underwater noise suppression structure for achieving the above object is an underwater noise suppression structure including the underwater noise reflection absorption structure configured in the columnar shape, and a plurality of underwater noise configured in the columnar column. The reflection-absorbing structure is arranged in the vertical direction and suspended in water.

According to this underwater noise suppression structure, a plurality of underwater noise reflection absorption structures configured in columns capable of efficiently suppressing underwater noise are installed so as to be suspended vertically in the water, and pile driving, etc. By installing it around the point where underwater noise is generated due to construction work or in the direction of suppressing the diffusion of underwater noise, it is possible to efficiently suppress underwater noise and suppress the diffusion of underwater noise.

Another underwater noise suppression structure for achieving the above object is an underwater noise suppression structure including the underwater noise reflection absorption structure configured in the columnar shape, and a plurality of underwater noise configured in the columnar column. The reflection-absorbing structure is arranged horizontally and hung in water.

According to this underwater noise suppression structure, a plurality of underwater noise reflection absorption structures configured in columns capable of efficiently suppressing underwater noise are installed so as to hang down in the water in the horizontal direction, and pile driving, etc. By installing it around the point where underwater noise is generated due to construction work or in the direction of suppressing the diffusion of underwater noise, it is possible to efficiently suppress underwater noise and suppress the diffusion of underwater noise.

Among the plurality of columnar underwater noise reflection and absorption structures arranged in the horizontal direction, the lower underwater noise reflection and absorption structure is filled with muddy water such as bentonite muddy water and muddy water due to cohesive soil, and underwater noise near the water surface is filled. The inside of the reflection absorption structure may be filled with gas. It is stable in water by filling the inside of the lower underwater noise reflection absorption structure with muddy water having a higher specific density than water, and the buoyancy effect is obtained by filling the inside of the upper underwater noise reflection absorption structure with gas. Can be done.

It is preferable to arrange an iron plate on the sound emitting surface on the back surface side of the sound incident surface of the underwater noise reflection absorbing structure. In particular, by combining an underwater noise reflection absorption structure containing gas inside and an iron plate placed on the back side of the sound incident surface, a small sound transmittance can be realized as a whole, making it difficult for underwater noise to pass through, and underwater noise. Can be efficiently suppressed.

It is preferable that the underwater noise suppression structure is configured to be movable in water by a ship. Thereby, for example, the underwater noise suppression structure can be moved to the next pile driving position according to the end of the pile driving and used repeatedly.

A plurality of the underwater noise reflection absorption structures can be hung in water so as to surround the underwater noise generation point when viewed from above or approach the generation point and partially open the arrangement. In this case, it may be arranged so as to land on the bottom of the water, but it may be arranged up to the middle of the water depth. By arranging a part of the underwater noise generation point so that it is open, for example, it is possible for the underwater noise suppression structure to be moved by the ship and the pile driving ship to enter and exit through the opened part. Become.

The underwater noise suppression method for achieving the above object is a direction in which the above-mentioned underwater noise reflection absorption structure or the above-mentioned underwater noise suppression structure is used to suppress the diffusion of the above-mentioned underwater noise around the generation point of the underwater noise and / or the above-mentioned underwater noise. By installing it in, it suppresses underwater noise.

According to this underwater noise suppression method, an underwater noise reflection absorption structure or an underwater noise suppression structure capable of efficiently suppressing underwater noise is provided around a point where underwater noise is generated due to construction such as pile driving and underwater noise. By installing in the diffusion suppression direction, underwater noise can be efficiently suppressed and the diffusion of underwater noise can be suppressed.

In the underwater noise suppression method, it is preferable to install the underwater noise reflection absorption structure or the underwater noise suppression structure so as to overlap with each other in the incident direction of the underwater noise. As a result, the underwater noise suppression effect is further improved.

According to the present invention, underwater noise reflection capable of efficiently suppressing underwater noise by combining surface reflection and internal absorption / reflection / resonance of underwater noise generated by construction such as pile driving is possible. It is possible to provide an absorption structure, an underwater noise suppression structure using the absorption structure, and an underwater noise suppression method.

2 are side views (a) to (f) schematically showing an underwater noise reflection absorbing structure and an underwater noise suppressing structure according to the present embodiment. It is a schematic diagram for demonstrating the reflection / transmission of the underwater noise in the underwater noise reflection absorption structure by this embodiment. 2 are side views (a) to (k) schematically showing another underwater noise reflection absorption structure and an underwater noise suppression structure according to the present embodiment. Top views (a) to (g) schematically show an arrangement example of an underwater noise suppression structure according to the present embodiment. FIG. 3 is a perspective view of a main part schematically showing a configuration example in which the underwater noise suppression structure of FIG. 1 (e) or FIG. 4 (g) has a frame structure. It is side view (a)-(f) which shows the arrangement example of the plurality of rows of the underwater noise suppression structure by this embodiment schematicly. It is a vertical sectional view (a) (b) which shows the example which the underwater noise suppression structure by this embodiment is arranged so as to surround the underwater noise generation point. It is a vertical cross-sectional view (a) (b) which shows typically the combination example of the underwater noise suppression structure and the submarine type underwater noise suppression structure by this embodiment. It is a vertical cross-sectional view (a) (b) which shows the example which the underwater noise suppression structure by this embodiment approaches an underwater noise generation point, and one is open. 1 (a) to 1 (e) are side views showing a modification of the underwater noise reflection absorption structure of FIGS. 1 (a), 1 (c) and 1 (e). It is a side view (a) (b) which shows the plate-shaped underwater noise reflection absorption structure by this embodiment. It is a main part perspective view which shows the modification of the underwater noise suppression structure by this embodiment schematicly. It is a figure which shows each condition of the experimental case in this experimental example. It is a schematic diagram of the experimental apparatus used for this experimental example. It is a graph which shows the experimental result about the presence or absence of an iron plate, and the difference in the outer shell shape in this experimental example. It is a graph which shows the frequency characteristic obtained in the experimental cases 1 to 4, 11 of FIG. It is a graph which shows the experimental result about the difference of the filling material in this experimental example. It is a graph which shows the frequency characteristic obtained in the experimental case 1, 4, 7-10 of FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is side views (a) to (f) schematically showing an underwater noise reflection absorbing structure and an underwater noise suppressing structure according to the present embodiment. FIG. 2 is a schematic diagram for explaining the reflection / transmission of underwater noise in the underwater noise reflection / absorption structure according to the present embodiment. In FIGS. 1, FIG. 2, and FIGS. 3, 6, and 11 described later, the underwater noise is assumed to be incident on the underwater noise reflection absorption structure and the underwater noise suppression structure from the left side of the figure.

In the underwater noise suppression structure 11 of FIG. 1A, a plurality of columnar underwater noise reflection / absorption structures 1 are arranged horizontally and arranged vertically to form a wall, and the underwater noise suppression structure 11 is suspended from the vicinity of the water surface. It was installed in.

The underwater noise reflection absorption structure 1 includes a columnar outer shell body 1a and an internal cavity 1b, and the internal cavity 1b can be filled with various filling materials. The outer shell body 1a is configured to have an internal cavity 1b from a metal material such as steel or stainless steel, a resin material such as vinyl chloride, polyethylene / polypropylene, FRP or the like.

Examples of the filling material filled in the internal cavity 1b include a sound absorbing material that absorbs underwater noise, a reflective material that reflects water, and a resonance material that resonates with underwater noise. Since the inside of the internal cavity 1b of the underwater noise reflection absorption structure 1 is a gas, a general sound insulating material / sound absorbing material can be filled in the internal cavity 1b and used. There are type sound absorbing materials, gas + cardboard, etc., and porous type sound absorbing materials include urethane, glass wool, rock wool, soft fiber slab, and the like. Reflective materials include gas + rubber, gas + urethane, and the like. Resonant materials include clay muddy water, bentonite muddy water, ethylene glycol, gel-like substances, resonators, and the like, and a combination of these with a gas is also possible.

The gas 31 is filled in the internal cavity 1b of each underwater noise reflection absorption structure 1 of the underwater noise suppression structure 11 of FIG. 1A. The gas 31 may be air, but may be another gas such as oxygen, carbon dioxide, nitrogen, helium, hydrogen, or ammonia, or a mixture of air and another gas.

The underwater noise suppression effect of the underwater noise reflection absorption structure 1 of FIG. 1A will be described with reference to FIG. The incident wave a on the underwater noise reflection absorbing structure 1 due to underwater noise is a reflected wave b reflected by the sound incident surface 1c on the circumferential surface of the outer shell 1a and a transmitted wave c transmitted through the sound incident surface 1c. Since the sound incident surface 1c reflected by the reflected wave b is curved, the reflection effect on the sound incident surface 1c is high, and the reflected wave b is from the water surface to the water bottom on the front side (left side) of the underwater noise reflection absorption structure 1. Underwater noise is suppressed by being widely dispersed in the direction of water, and in this dispersion process, the underwater noise is attenuated, absorbed at the bottom of the water, and released from the water surface into the air. On the other hand, the transmitted wave c is a transmitted wave that is reflected in the internal cavity 1b and becomes a reflected wave d, and is also transmitted through the gas 31 in the internal cavity 1b, emitted from the sound emitting surface 1d on the back surface side, and propagates in water. It is reduced by becoming e. As described above, the transmitted wave c becomes the reflected wave d and the transmitted wave e in the process of propagating from the underwater noise reflection absorbing structure 1 into the water, and the sound pressure is lowered. As described above, the underwater noise is reduced and suppressed by the underwater noise reflection absorbing structure 1. If the sound intensity transmittance is calculated from the acoustic impedance of seawater and air, ignoring the material of the underwater noise reflection absorption structure, a transmittance of 0.1% is obtained, which is considerable in the process of propagating from seawater to air. It can be seen that the sound pressure decreases.

The underwater noise suppression structure 12 of FIG. 1B has the same configuration as that of FIG. 1A, but is composed of gas and a sound absorbing material in the internal cavity 1b of the outer shell 1a of the underwater noise reflection absorption structure 1. The filler 32 is filled. The sound absorbing material may be a porous sound absorbing material such as urethane or glass wool, cardboard or the like. Since the filler 32 contains a sound absorbing material in addition to a gas such as air, the sound pressure level of the transmitted wave c in the internal cavity 1b of FIG. 2 is further lowered by the sound absorbing material, and the sound is discharged from the sound emitting surface 1d into the water. The transmitted wave e is reduced in the process of propagating. As described above, by using the gas and the sound absorbing material in the internal cavity 1b, it is possible to suppress the underwater noise by utilizing the sound absorbing material having a small suppressing effect in water. The filler 32 may be a gas and a reflective material, or a gas and a resonance material.

The underwater noise suppression structure 13 of FIG. 1 (c) has the same configuration as that of FIG. 1 (a), but the gas 31 is filled in the internal cavity 1b of the outer shell 1a of the underwater noise reflection absorption structure 1. In addition, a porous type sound absorbing material 35 such as urethane is arranged. The porous sound absorbing material 35 has a large number of relatively small pyramid-shaped protrusions 35a, and has a flat portion 35b on the opposite side of the large number of protrusions 35a. The porous type sound absorbing material 35 is arranged in the central portion so as to be pushed into the internal cavity 1b, and is fixed at the upper part, the lower part, or the like.

According to the underwater noise suppression structure 13 of FIG. 1 (c), the sound absorption area is increased by a large number of pyramid-shaped protrusions 35a of the porous sound absorbing material 35 arranged in the internal cavity 1b of the underwater noise reflection absorption structure 1. By efficiently absorbing and reducing the transmitted wave c and the reflected wave d in FIG. 2, the effect of suppressing underwater noise is increased.

The underwater noise suppression structure 14 of FIG. 1D has the same configuration as that of FIG. 1A, but in the inner cavity 1b of the upper outer shell body 1a among the plurality of underwater noise reflection absorption structures 1. The gas 31 is filled, the inner cavity 1b of the intermediate outer shell 1a is filled with the filler 33 composed of the gas 31 and the muddy water 32, and the inner cavity 1b of the lower outer shell 1a is filled with only the muddy water 34. .. The muddy waters 32 and 34 are, for example, a mixture of cohesive soil or bentonite and water, and have a higher specific density than water. The muddy water 32 and the muddy water 34 may be made of the same material or different materials.

The underwater noise reflection absorption structure 1 filled with the filler 33 of the muddy water 32 and the gas 31 resonates with the underwater noise, the transmitted wave e in FIG. 2 is reduced, the effect of suppressing the underwater noise is increased, and the muddy water 34 The underwater noise reflection absorption structure 1 filled with only the underwater noise resonates with the underwater noise, the transmitted wave e in FIG. 2 is reduced, and the effect of suppressing the underwater noise is further increased. Further, the underwater noise reflection absorbing structure 1 filled with the gas 31 can obtain the buoyancy effect of the underwater noise suppressing structure 14, and the underwater stabilizing effect is obtained by filling the filler 33 containing muddy water and the muddy water 34. Can be obtained.

The underwater noise suppression structure 15 of FIG. 1 (e) has the same configuration as that of FIG. 1 (a), but is formed on the sound emitting surface 1d on the back surface side of the outer shell 1a of the plurality of underwater noise reflection absorption structures 1. The iron plate 40 is arranged so as to be in contact with each other. The transmitted wave e of FIG. 2 emitted from each sound emitting surface 1d is reduced by the iron plate 40, and the effect of suppressing underwater noise is further increased. By filling the internal cavity 1b with a filler composed of gas and muddy water, the effect of suppressing underwater noise is further increased.

In the underwater noise suppression structure 16 of FIG. 1 (f), the gas 31 is filled in the internal cavity 2b of the outer shell body 2a of the plurality of semi-cylindrical underwater noise reflection absorption structures 2 in the same manner as in FIG. 1 (c). At the same time, the porous sound absorbing material 35 is arranged, and the iron plate 40 is arranged in contact with the flat surface 2d on the opposite side of the sound incident surface 2c of the semicircular outer shell body 2a. The sound absorbing area is increased by the large number of pyramid-shaped protrusions 35a of the porous sound absorbing material 35, and the transmitted wave c in FIG. 2 is efficiently absorbed and reduced, and the transmitted wave e in FIG. 2 is reduced by the iron plate 40 in water. The noise suppression effect is further increased.

FIG. 3 is a side view (a) to (k) schematically showing another underwater noise reflection absorbing structure and an underwater noise suppressing structure according to the present embodiment.

The underwater noise suppression structure 17 of FIG. 3A is a structure in which a plurality of triangular columnar underwater noise reflection / absorption structures 4 are installed in water in the same manner as in FIG. 1A. The underwater noise reflection absorption structure 4 includes a triangular columnar outer shell body 4a and an inner cavity 4b, one apex of the outer shell body 4a faces vertically downward, and the inner cavity 4b is filled with a gas 31 such as air. Has been done.

According to the underwater noise reflection absorption structure 4 of FIG. 3A, when the incident wave a due to the underwater noise of FIG. 2 is incident on the inclined sound incident surface 4c of the outer shell 4a, the sound incident surface 4c becomes the inclined surface. Therefore, the reflection effect on the sound incident surface 4c is high, and the reflected wave travels toward the water bottom surface to generate sound absorption on the water bottom surface, while the transmitted wave c transmitted through the sound incident surface 4c is reflected in the internal cavity 4b. It is reflected as a wave d, and is reduced by passing through the gas 31 in the internal cavity 4b, which reduces the transmitted wave e emitted from the sound emitting surface 4d opposite to the sound incident surface 4c. Underwater noise is reduced and suppressed by the underwater noise reflection absorption structure 4.

Further, according to the underwater noise suppression structure 17 of FIG. 3A, each underwater noise reflection absorption structure is formed by forming a plurality of triangular columnar underwater noise reflection absorption structures 4 in a wall shape and installing them in water. Due to the effect of suppressing underwater noise by 4, it is possible to reduce the underwater noise incident from the left side of the figure and suppress the diffusion to the right side of the figure.

The underwater noise suppression structure 18 of FIG. 3B has the same configuration as that of FIG. 3A, but is composed of gas and a sound absorbing material in the internal cavity 4b of the outer shell 4a of the underwater noise reflection absorption structure 4. The filler 32 is filled. The sound absorbing material may be a porous sound absorbing material such as urethane, cardboard, glass wool or the like. Since the filler 32 contains a sound absorbing material in addition to a gas such as air, the transmitted wave c in FIG. 2 in the internal cavity 4b is further reduced by the sound absorbing material, and is transmitted from the sound emitting surface 4d on the opposite side. The wave e is further reduced, and the effect of suppressing underwater noise is increased.

The underwater noise suppression structure 19 of FIG. 3C has the same configuration as that of FIG. 3A, but the gas 31 is filled in the internal cavity 4b of the outer shell 4a of the underwater noise reflection absorption structure 4. In addition, the same porous type sound absorbing material 35 as in FIG. 1 (c) is arranged. According to the underwater noise suppression structure 19, the sound absorption area is increased by the large number of pyramid-shaped protrusions 35a of the porous sound absorbing material 35 arranged in the internal cavity 4b of the underwater noise reflection absorption structure 4, and the transmitted wave of FIG. 2 is transmitted. By efficiently absorbing and reducing c and the reflected wave d, the effect of suppressing underwater noise is increased.

The underwater noise suppression structure 20 of FIG. 3D has the same configuration as that of FIG. 3A, but in the inner cavity 4b of the upper outer shell body 4a among the plurality of underwater noise reflection absorption structures 4. The gas 31 is filled, the inner cavity 4b of the intermediate outer shell 4a is filled with the filler 33 composed of the gas 31 and the muddy water 32, and the inner cavity 4b of the lower outer shell 4a is filled with only the muddy water 34. .. Similar to FIG. 1D, the effect of suppressing underwater noise is further increased, and the buoyancy effect and the underwater stabilizing effect can be obtained.

The underwater noise suppression structure 21 of FIG. 3 (e) has the same configuration as that of FIG. 3 (a), but has an inclined sound emitting surface 4d on the back surface side of the outer shell body 4a of the plurality of underwater noise reflection absorption structures 4. The iron plate 40 is arranged on the side. The transmitted wave e of FIG. 2 emitted from each sound emitting surface 4d is reduced by the iron plate 40, and the effect of suppressing underwater noise is further increased. By filling the internal cavity 4b with a filler composed of gas and muddy water, the effect of suppressing underwater noise is further increased.

In the underwater noise suppression structure 22 of FIG. 3 (f), the gas 31 is filled in the inner cavity 5b of the outer shell body 5a of the plurality of semi-triangular columnar underwater noise reflection absorption structures 5 in the same manner as in FIG. 1 (c). At the same time, the porous sound absorbing material 35 is arranged, and the iron plate 40 is arranged in contact with the flat surface 5d on the opposite side of the sound incident surface 5c of the semi-triangular outer shell body 5a. The sound absorbing area is increased by the large number of pyramid-shaped protrusions 35a of the porous sound absorbing material 35, and the transmitted wave c in FIG. 2 is efficiently absorbed and reduced, and the transmitted wave e in FIG. 2 is reduced by the iron plate 40 in water. The noise suppression effect is further increased.

The underwater noise suppression structure 23 of FIG. 3 (g) is a structure in which a plurality of triangular columnar underwater noise reflection / absorption structures 7 are installed underwater in the same manner as in FIG. 3 (a), and each of the plurality of underwater noise reflection / absorption structures is absorbed. The structure 7 is arranged such that one apex of the triangular columnar outer shell 7a faces in the horizontal direction, and one side of the three sides of the outer shell 4a at the same position is arranged on the same vertical line, and the internal cavity 7b is arranged. Is filled with gas 31. When the incident wave a due to the underwater noise in FIG. 2 is incident on the inclined sound incident surfaces 7c and 7d of the outer shell body 7a, the sound incident surfaces 7c and 7d are inclined surfaces having different inclination directions, so that the sound incident surfaces 7c and 7d The reflected wave has a high reflection effect, and the reflected wave travels toward the water surface and the water bottom surface to be emitted from the water surface and sound is absorbed at the water bottom surface. It is reflected as a reflected wave d, and is reduced by passing through the gas 31 in the internal cavity 7b, whereby the transmitted wave e emitted from the opposite sound emitting surface 7e of the sound incident surfaces 7c and 7d is reduced. However, underwater noise is suppressed. According to the underwater noise suppression structure 23, the underwater noise suppression effect of the underwater noise reflection absorption structure 7 can reduce the underwater noise incident from the left side of the figure and suppress the diffusion to the right side of the figure.

The underwater noise suppression structure 24 of FIG. 3 (h) has the same configuration as that of FIG. 3 (g), but the internal cavity 7b of the underwater noise reflection absorption structure 7 is filled with a filler 32 made of gas and a sound absorbing material. Has been done. Since the filler 32 contains a porous sound absorbing material such as urethane and a sound absorbing material such as cardboard and glass wool in addition to a gas such as air, the transmitted wave c in FIG. 2 in the internal cavity 7b is further increased by the sound absorbing material. It is reduced, the transmitted wave e emitted from the sound emitting surface 7e on the opposite side is further reduced, and the effect of suppressing underwater noise is increased.

The underwater noise suppression structure 25 of FIG. 3 (i) is formed in the inner cavity 7b of the outer shell 7a of the plurality of triangular columnar underwater noise reflection absorption structures 7 similar to those of FIG. 3 (g). Similarly, the gas 31 is filled and the porous sound absorbing material 35 is arranged, and the iron plate 40 is arranged in contact with the flat surface 7e which is the sound emitting surface of the outer shell body 5a. The sound absorbing area is increased by the large number of pyramid-shaped protrusions 35a of the porous sound absorbing material 35, and the transmitted wave c in FIG. 2 is efficiently absorbed and reduced, and the transmitted wave e in FIG. 2 is reduced by the iron plate 40 in water. The noise suppression effect is further increased. In addition, in FIG. 3 (i), the iron plate 40 may be omitted.

The underwater noise suppression structure 26 of FIG. 3 (j) has the same configuration as that of FIG. 3 (g), but in the inner cavity 7b of the upper outer shell 7a among the plurality of underwater noise reflection absorption structures 7. The gas 31 is filled, the inner cavity 7b of the intermediate outer shell 7a is filled with the filler 33 composed of the gas 31 and the muddy water 32, and the inner cavity 7b of the lower outer shell 7a is filled with only the muddy water 34. .. Similar to FIG. 1D, the effect of suppressing underwater noise is further increased, and the buoyancy effect and the underwater stabilizing effect can be obtained.

The underwater noise suppression structure 27 of FIG. 3 (k) has the same configuration as that of FIG. 3 (g), but has an upright sound emitting surface 7e on the back surface of the outer shell 7a of the plurality of underwater noise reflection absorption structures 7. The iron plate 40 is arranged on the side. The transmitted wave e of FIG. 2 emitted from each sound emitting surface 7e is reduced by the iron plate 40, and the effect of suppressing underwater noise is further increased. By filling the internal cavity 7b with a filler composed of gas and muddy water, the effect of suppressing underwater noise is further increased.

As described above, according to the underwater noise suppression structures 11 to 27 of FIGS. 1 (a) to 1 (f) and FIGS. 3 (a) to 3 (k), a plurality of columnar underwater noise reflection absorption structures 1 to 5 By arranging, 7 in the horizontal direction and constructing them in a wall shape and installing them in water, the reflected waves in each of the underwater noise reflection absorption structures 1 to 5 and 7 are absorbed at the bottom of the water and released from the water surface into the air. It is possible to reduce the underwater noise incident from the left side of the figure and suppress the diffusion to the right side of the figure due to the effect of suppressing the underwater noise due to the decrease and the sound pressure decrease in the process of propagating the transmitted wave from the gas to the water. This makes it possible to prevent adverse effects on aquatic organisms such as fish due to underwater noise generated during construction work such as pile driving.

Further, it is desirable that the width Z (FIG. 1 (f)) of the underwater noise reflection absorbing structures 1 to 5 and 7 in the sound transmission direction is 50 mm or more. Further, in the underwater noise suppression structures 11 to 27, the underwater noise reflection / absorption structures having the same shape are arranged, but the underwater noise reflection / absorption structures having different shapes and sizes may be arranged at the top and bottom, and the inside. The filling material for the cavity may also be changed for each underwater noise reflection absorption structure. For example, the filling material is such that the underwater noise suppression structure near the water surface is filled with a gas such as air to secure buoyancy, and the filling material is below. It may be filled with muddy water or the like (see FIGS. 1 (d) and 3 (d) (j)).

Further, when filling the internal cavities 1b to 5b and 7b in the underwater noise reflection absorbing structures 1 to 5 and 7 with a gas such as air, air or the like is not supplied continuously as in the air bubble curtain. Can be expected to have a sound insulation effect. Further, as shown in FIG. 1A, a columnar shape (cylindrical shape) having a shape and structure that can withstand water pressure can be obtained, or a gas can be filled in the underwater noise reflection absorption structure 1 at a pressure corresponding to the water pressure to reduce the water pressure. It can withstand, there is no problem of gas volume reduction due to water depth in the air bubble curtain, and it is possible to hold a gas layer of a predetermined volume necessary for measures against underwater noise even under such water pressure conditions. An air valve curtain can be used in combination at an appropriate water depth, whereby the sound insulation effect can be further enhanced.

Next, an arrangement example of the underwater noise suppression structure according to the present embodiment will be described with reference to FIG. FIG. 4 is a top view (a) to (g) schematically showing an arrangement example of the underwater noise suppression structure according to the present embodiment.

The underwater noise suppression structure 41 of FIG. 4A includes the plurality of columnar underwater noise reflection absorption structures 1 to 5, 7 of FIGS. 1 (a) to 1 (f) and FIGS. 3 (a) to 3 (k). It is arranged in the vertical direction so that the whole body hangs down from the water surface in the horizontal direction, and is arranged in a circular shape so as to surround the underwater noise generation point 50 such as the pile driving point when viewed from the upper surface. Further, the underwater noise reflection absorption structures 1 to 5 and 7 may be arranged in a square shape so as to surround the underwater noise generation point 50 as in the underwater noise suppression structure 47 of FIG. 4 (g).

The underwater noise suppression structure 42 of FIG. 4B has a plurality of columnar underwater noise reflection and absorption structures 1 to 5 and 7 in a semicircular shape surrounding the underwater noise generation point 50 and having an open portion 42a. It is arranged and may have a C-shape in which the arc-shaped portion 42b shown by the broken line is further extended. The underwater noise suppression structure 43 of FIG. 4C has a plurality of columnar underwater noise reflection and absorption structures 1 to 5 and 7 in a semi-octagonal shape surrounding the underwater noise generation point 50 and having an open portion 43a. It may be arranged and may have a shape having one side 43b shown by a broken line, or may have a shape having another side 43c. The underwater noise suppression structure 44 of FIG. 4D has an open portion 44a that surrounds the underwater noise generation points 50 and has an open side of the plurality of columnar underwater noise reflection and absorption structures 1 to 5,7. It is arranged in a square shape. The underwater noise suppression structure 45 of FIG. 4 (e) has an open portion 45a that surrounds the underwater noise generation points 50 and has an open side of the plurality of columnar underwater noise reflection and absorption structures 1 to 5,7. It is arranged in a triangular shape. In the underwater noise suppression structure 46 of FIG. 4 (f), a plurality of columnar underwater noise reflection absorption structures 1 to 5 and 7 are arranged in a straight line so as to face the underwater noise generation point 50. ..

The underwater noise suppression structures 41 and 47 of FIGS. 4 (a) and 4 (g) can suppress underwater noise in all directions in the water area. Further, the underwater noise suppression structures 42 to 46 of FIGS. 4 (b) to 4 (f) are installed around the underwater noise generation point 50 in a direction in which the underwater noise is desired to be suppressed in the water area, and the underwater noise in that direction is desired. Can suppress the diffusion of.

In FIGS. 4 (a) to 4 (g), the underwater noise reflection and absorption structures 1 to 5 and 7 are arranged horizontally so as to have the shape of each upper surface, but in FIGS. 4 (a) and 4 (b), they are substantially arcuate. In FIGS. 4 (c) to 4 (g), the structure is linear.

Further, the underwater noise suppression structures 41 to 47 can be configured as a frame structure in the same manner as the pollution prevention frame for preventing contamination of the surrounding water area at the time of dredging. For example, as shown in FIG. 5, at the position of the iron plate 60 shown by the broken line on the side surface of the frame structure, the underwater noise suppression structure 47 of FIG. 4 (g) composed of the underwater noise suppression structure 11 of FIG. 1 (a) is provided. The underwater noise suppression structure 47 having a frame structure is configured by arranging the underwater noise suppression structure 47 so as to hang down or by fixing each underwater noise reflection absorption structure 1 of the underwater noise suppression structure 47 to the iron plate 60. Similarly, underwater noise suppression structures 41 to 46 having a frame structure can be configured. According to the frame structure of FIG. 5 in which the plurality of underwater noise reflection absorption structures 1 are fixed to the iron plate 60, the same underwater noise reduction effect as in FIG. 1 (e) can be obtained.

The underwater noise suppression structures 41 to 47 having the frame structure as described above can be moved by a tugboat or a tugboat and fixed at a predetermined position. In this case, by providing the open portions 41a and 47a shown by the broken lines in a part of the circular shape or the square shape of the underwater noise suppression structures 41 and 47 of FIGS. 4 (a) and 4 (g), the underwater noise generation point 50 is hit. It can be moved even if there are piles installed. Further, by determining the dimensions of the open portions 41a and 47a according to the size of the ship entering in advance, even if the underwater noise suppression structures 41 and 47 are installed at predetermined positions in advance, the underwater piles are used. A pile driving ship or the like can enter the driving point 50. Further, since the underwater noise suppression structures 42 to 45 have open portions 42a to 45a, they can be moved by a push ship or a tugboat, and can be entered by a pile driving ship or the like. By configuring the underwater noise suppression structures 41 to 47 of the frame structure so as to be movable in this way, for example, the underwater noise suppression structures 41 to 47 are moved to the next pile driving position according to the end of the pile driving. Can be used repeatedly. It is also possible to install the underwater noise suppression structures 41 to 47 below the water surface so that the upper part thereof can be passed by a ship.

Next, an example of arranging a plurality of rows of the underwater noise suppression structure according to the present embodiment will be described with reference to FIG. FIG. 6 is side views (a) to (f) schematically showing an arrangement example of a plurality of rows of the underwater noise suppression structure according to the present embodiment.

In the example of FIG. 6A, the underwater noise suppression structures 11 and 11 of FIG. 1A are arranged in two rows so that the underwater noise reflection absorption structures 1 approach each other, and FIG. 6B is shown. In the example, the two rows of underwater noise suppression structures 11 and 11 are arranged in two rows so as to be separated from each other. In the example of FIG. 6 (c), the underwater noise suppression structure 11 is provided with the underwater noise reflection absorption structure 1A having the same configuration as the underwater noise reflection absorption structure 1 but having a smaller diameter. In the example of FIG. 6D, the underwater noise reflection absorbing structure 1 is arranged in the gap between the underwater noise reflection absorbing structures 1 of the underwater noise suppressing structure 11. In the example of FIG. 6 (e), the arrangement is the same as that of FIG. 6 (d), but the underwater noise reflection absorption structure 1 is slightly separated in the vertical direction and the horizontal direction so that the interval w can be formed. It is placed in. In the example of FIG. 6 (f), the underwater noise suppression structure 11A in which a plurality of small diameter underwater noise reflection absorption structures 1A are arranged in a row is arranged slightly apart from the underwater noise suppression structure 11.

The underwater noise suppression structures of FIGS. 6A to 6F are arranged in a plurality of rows so as to overlap in the incident direction of the underwater noise, and the structures arranged in a plurality of rows do not necessarily have to be in close contact with each other. As shown in FIGS. 6 (b), 6 (e) and 6 (f), they may be separated from each other, and in either case, the effect of suppressing underwater noise is increased. Further, the separation distance between the underwater noise suppression structures may be set according to the frequency of the underwater noise to be suppressed. 6 (a) to 6 (f) have described an example in which a plurality of rows of the underwater noise suppression structures 11 of FIG. 1 (a) are arranged, but FIGS. 1 (b) to 1 (f) and FIGS. 3 (a) have been described. )-(K) may be arranged in a plurality of rows in the same manner, or the underwater noise suppression structures having different shapes and fillers from the underwater noise suppression structures 11 to 27 may be combined. Multiple columns may be arranged. Further, the length (depth) in the vertical direction of each of the plurality of rows of underwater noise suppression structures may be different.

Further, when a plurality of rows are arranged, as shown in FIG. 6E, even if there is an interval w between the underwater noise reflection absorption structures 1, the underwater noise is suppressed in the process of passing through the narrow interval w and diffusing. , Underwater noise leakage can be suppressed.

FIG. 7 is a vertical cross-sectional view (a) and (b) showing an example in which the underwater noise suppression structure according to the present embodiment is arranged so as to surround the underwater noise generation point. The example of FIG. 7 (a) is the same as the underwater noise suppression structure 41 of FIG. 4 (a) so as to form a bottoming type that surrounds the underwater noise generation point 50 due to pile driving or the like and bottoms on the water bottom. By installing the underwater noise suppression structure 41A having the above configuration, underwater noise is suppressed in the range from the water surface to the water bottom. In the example of FIG. 7 (b), the underwater noise suppression structure 41B having the same configuration as the underwater noise suppression structure 41 of FIG. 4 (a) is installed so as to form an intermediate arrangement type that is arranged from the water surface to the water depth intermediate position. By doing so, underwater noise is suppressed in the range from the water surface to the middle of the water depth.

FIG. 8 is a diagram (a) and (b) showing an example of a combination of the underwater noise suppression structure according to the present embodiment and the submarine type underwater noise suppression structure. In the example of FIG. 8A, an underwater noise suppression structure 51 having a high underwater noise suppression effect is installed on the bottom surface of the water to suppress underwater noise in the range from the bottom of the water to the middle of the water depth, and FIG. 7B ), The underwater noise suppression structure 41B is installed in the intermediate arrangement type to suppress the underwater noise in the range from the water surface to the middle of the water depth, and to suppress the underwater noise in the range from the water surface to the water bottom as a whole.

The underwater noise suppression structures 41A and 41B of FIGS. 7 (a) and 7 (b) and 8 (a) may have the same configuration as the underwater noise suppression structure 47 of FIG. 4 (g). Further, for example, as shown in FIG. 9A, the underwater noise suppression structure of FIG. 4B is such that one side opens and approaches the underwater noise generation point 50 at the opening portion 42a (FIG. 4B). By installing the underwater noise suppression structure 42A having the same configuration as the body 42 in a landing type, underwater noise is suppressed in the range from the water surface to the bottom in one side to suppress the diffusion of underwater noise from the underwater noise generation point 50. It can be suppressed. Further, as shown in FIG. 9B, by installing the underwater noise suppression structure 42B having the same configuration as the underwater noise suppression structure 42 of FIG. 4B in the intermediate arrangement type, the underwater noise generation point 50 can be used. Suppressing the diffusion of underwater noise It is possible to suppress underwater noise in the range from the water surface to the middle of the water depth in one side. The underwater noise suppression structures 42A and 42B of FIGS. 9A and 9B may have the same configuration as the underwater noise suppression structures 43 to 46 of FIGS. 4C to 4f.

In the example of FIG. 8B, a submarine type underwater noise suppression structure 51 is installed on the bottom surface of the water to suppress underwater noise below, and FIG. 4 (f) is above the upper surface of the underwater noise suppression structure 51. By installing a linear underwater noise suppression structure 46 such as, the underwater noise is suppressed from the upper surface of the underwater noise suppression structure 51 to the water surface, and the underwater noise is suppressed in the range from the water surface to the bottom as a whole. be. As the underwater noise suppression structure 51 of FIGS. 8A and 8B, for example, the structure previously proposed by the present inventors in Japanese Patent Application No. 2020-014408 can be used.

Next, a modification of the underwater noise reflection absorption structure 1 of FIGS. 1 (a), 1 (c), and 1 (e) will be described with reference to FIGS. 10 (a) to 10 (e). The underwater noise reflection / absorption structure 9A of FIG. 10A has a large number of relatively small pyramid-shaped protrusions 36a in FIG. 1C and has a flat portion 36b on the opposite side of the large number of protrusions 36a. The porous type sound absorbing material 36 is further arranged, and the flat portion 35b of the porous type sound absorbing material 35 and the flat portion 36b of the porous type sound absorbing material 36 are bonded together. In the internal cavity 1b, the sound absorbing area is increased by a large number of pyramid-shaped protrusions 35a on the incident side of the transmitted wave c, and the sound absorbing area is increased by a large number of pyramid-shaped protrusions 36a on the incident side of the reflected wave d. By efficiently absorbing and reducing c and the reflected wave d, the effect of suppressing underwater noise is further increased.

The underwater noise reflection / absorption structure 9B of FIG. 10B is composed of the underwater noise reflection / absorption structures 2 and 3 divided into semicircles, and has a columnar shape as a whole as in FIG. 1A. There is. The semi-cylindrical underwater noise reflection / absorption structure 2 is located on the incident side of the underwater noise, the semi-cylindrical underwater noise reflection / absorption structure 3 is located on the opposite side, and the internal cavity of the underwater noise reflection / absorption structure 2 is located. A porous sound absorbing material 35 is arranged in 2b as in FIG. 1 (f).

The outer shell 2a of the underwater noise reflection absorption structure 2 has a semi-circular internal cavity 2b, a sound incident surface 2c on the circumferential surface, and a flat surface 2d formed on the opposite side of the sound incident surface 2c. The outer shell 3a of the underwater noise reflection absorption structure 3 has a semi-circular internal cavity 3b, a flat surface 3d serving as a sound incident surface, and a sound emitting surface 3c on the circumferential surface. The underwater noise reflection absorption structures 2 and 3 are integrated by laminating the flat surface 2d and the flat surface 3d with an adhesive or the like. The internal cavities 2b and 3b are filled with a gas 31 such as air. Instead of the gas 31, a sound absorbing material, a reflective material, a resonant material, a gas and a sound absorbing material, a gas and a reflective material, a gas and a resonant material, a gas and muddy water, or muddy water may be filled, and further, the internal cavity 2b may be filled. And the internal cavity 3b may be filled with different fillers.

According to the underwater noise reflection absorption structure 9B of FIG. 10B, the sound absorption area is increased by a large number of pyramid-shaped protrusions 35a in the internal cavity 2b, and the transmitted wave c of FIG. 2 is efficiently absorbed and reduced. Finally, the transmitted wave e emitted from the sound emitting surface 3c on the circumferential surface of the underwater noise reflection absorbing structure 3 is further reduced, and the effect of suppressing the underwater noise is increased.

In the underwater noise reflection / absorption structure 9C of FIG. 10C, the underwater noise reflection / absorption structures 2 and 3 divided into semicircles are opposed to the flat surfaces 2d and 3d as in FIG. 10B. It is integrated by laminating with an adhesive or the like, and absorbs and reduces underwater noise.

The underwater noise reflection / absorption structure 9D of FIG. 10D has a large number of relatively small pyramid-shaped protrusions 36a in the internal cavity 3b of the semicircular underwater noise reflection / absorption structure 3 in FIG. 10B. In addition, a porous sound absorbing material 36 such as urethane having a flat portion 36b is arranged on the opposite side of a large number of protrusions 36a. In the internal cavity 2b of the underwater noise reflection absorption structure 2, the sound absorption area is increased by a large number of pyramid-shaped protrusions 35a on the incident side of the transmitted wave c, and the incident side of the reflected wave d in the internal cavity 3b of the underwater noise reflection absorption structure 3. The sound absorbing area is increased by the large number of pyramid-shaped protrusions 36a, and the transmitted wave c and the reflected wave d in FIG. 2 are efficiently absorbed and reduced, so that the effect of suppressing underwater noise is further increased.

The underwater noise reflection absorbing structure 9E of FIG. 10E is a urethane having a relatively small pyramid-shaped protrusion 37a on the semicircular inner surface of the sound emitting surface 3c of the underwater noise reflection absorbing structure 3 in FIG. 10B. The porous sound absorbing material 37 such as the above is bent and arranged so that the flat surface 37b follows the semicircular inner surface, and the sound absorbing area and the reflecting area are increased by the pyramid-shaped protrusions 37a to efficiently absorb and reduce underwater noise.

It should be noted that a plurality of underwater noise reflection absorption structures 9A to 9E of FIGS. 10A to 10E may be arranged in the same manner as in FIGS. 1A, 1C and 1E to form an underwater noise suppression structure. can. The underwater noise suppression structure composed of the underwater noise reflection / absorption structure 9C of FIG. 10C is a two-row underwater noise suppression structure composed of semicircular underwater noise reflection / absorption structures 2 and 3. It can be considered as a modification of FIG. 6A. Further, the underwater noise reflection / absorption structure 4 of FIGS. 3 (a) and 3 (c) may be formed into a semi-triangular shape to form a divided structure similar to that of FIGS. 10 (b) to 10 (e).

Next, a modification of the underwater noise reflection absorption structure according to the present embodiment will be described with reference to FIGS. 11 (a) and 11 (b). In the underwater noise reflection absorption structure 10A of FIG. 11A, the outer shell body 10a is formed in a plate shape as a whole, the sound incident surface is formed into wavy unevenness 10c, and the underwater noise incidented by the wavy unevenness 10c is generated. Efficiently reflects and reduces underwater noise. In the underwater noise reflection absorption structure 10B of FIG. 11B, the sound incident surface is formed into small triangular or serrated unevenness 10d, and the underwater noise incident on the unevenness 10d is efficiently reflected to reduce the underwater noise. Let me. In the underwater noise reflection and absorption structures 10A and 10B of FIGS. 11A and 11B, the internal cavity 10b may be a gas 31, but a sound absorbing material or a resonance material may be filled. Further, the underwater noise suppression structure composed of the underwater noise reflection absorption structures 10A and 10B extends in the horizontal direction (vertical direction on the paper surface) and is entirely formed in a plate shape, and may be composed of one plate-shaped member. It may be composed of a combination of vertically and / or horizontally divided divided plate-shaped members, and in any case, it is installed so as to hang down in water.

In FIGS. 1 (a) to 1 (f) and FIGS. 3 (a) to 3 (k), a plurality of columnar underwater noise reflection absorption structures are arranged in the horizontal direction, but the present invention is not limited to this, and the columnar underwater noise is not limited to this. A plurality of reflection-absorbing structures may be arranged in the vertical direction to form an underwater noise suppression structure. For example, as shown in FIG. 12, the underwater noise suppression structure 70 configured by arranging a plurality of columnar underwater noise reflection absorption structures 1 in the vertical direction may be installed so as to be suspended in water. The filling material to be filled in the internal cavity of the underwater noise suppression structure 70 is preferably determined in consideration of the buoyancy effect and the underwater stabilization effect.

<Experimental example>
Underwater noise suppression structures were produced under different conditions as shown in Experimental Cases 1 to 14 shown in FIG. Experimental cases 3 to 10 corresponding to FIGS. 1 (a), (b), (d), and (e) having a circular outer shell shape use a PVC pipe having a diameter of 100 mm as the outer shell body, and the outer shell shape is triangular (▽). ), The experimental cases 11 to 14 corresponding to FIGS. 3 (a) and 3 (g) used an elongated plastic container having a side of about 120 mm as an outer shell. This underwater noise suppression structure was installed in a 500 L plastic water tank shown in FIG. 14, and the underwater noise when the steel pipe was hit was measured by a sound pressure gauge. It should be noted that the experimental case 1 is the case where nothing is installed, and the experimental case 2 is the case where only the iron plate (thickness 2 mm) is installed.

FIG. 15 is a graph showing the experimental results regarding the presence / absence of the iron plate and the difference in the outer shell shape according to the experimental cases 1 to 11, and FIG. 16 is a graph showing the frequency characteristics obtained in the experimental cases 1 to 4 and 11. Is. As is clear from FIG. 15, when only the iron plate of the experimental case 2 and the filling material of the experimental cases 6 and 14 are tap water, the sound pressure level reducing effect is almost nonexistent or considerably small, whereas the present embodiment is used. In Experimental Cases 3, 4, 5, 11, 12, and 13, it was confirmed that the sound pressure level reducing effect was large, and from FIG. 16, it was confirmed that the sound pressure level reducing effect was obtained in a wide frequency band. In the results of this experiment, in particular, the experimental case 11 in which the outer shell shape is triangular (▽), the filling material is air, and the back iron plate is arranged has the highest sound pressure level reduction effect, and the reduction effect of 18 dB was confirmed.

FIG. 17 is a graph showing the experimental results regarding the difference in the filling material, and FIG. 18 is a graph showing the frequency characteristics obtained in the experimental cases 1, 4, 7 to 10. As is clear from FIG. 17, the sound insulation effect is large in the experimental cases 9 and 10 in which the filling material is muddy water with 10% bentonite, and the sound insulation effect is the highest in the experimental case 10 in which half is filled with 10% bentonite and the other half is filled with air. It was confirmed to be large. Focusing on the frequency characteristics from FIG. 18, the sound pressure level was reduced in all frequency bands in the experimental cases 4 of air and the experimental cases 9 and 10 of muddy water with 10% bentonite.

Although the embodiment for carrying out the present invention has been described above, the present invention is not limited to these, and various modifications can be made within the scope of the technical idea of the present invention. For example, it goes without saying that the number of vertical underwater noise reflection absorbing structures in FIGS. 1 (a) to 1 (f) and FIGS. 3 (a) to 3 (k) can be increased or decreased as needed.

Further, it goes without saying that the present invention can be applied not only to pile driving at the time of construction of an offshore wind power generation facility but also to other underwater sounds. Further, the present invention can be applied to the case where it is desired to avoid the emission of noise from the water into the air in a place where a person lives around the noise generation point, and in particular, the underwater noise shown in FIGS. 3 (a) to 3 (f). According to the suppression structures 17 to 22, the reflected wave of the underwater noise on the sound incident surface of the underwater noise reflection absorption structure is directed toward the bottom of the water and absorbed at the bottom of the water, effectively releasing the noise from the water to the air. Can be reduced.

Further, when constructing the underwater noise suppression structure according to the present embodiment, it is preferable to fix each underwater noise reflection absorption structure by installing a float or a weight as necessary, or to fix it to the frame.

Further, when the underwater noise reflection absorption structure is composed of a quadrangular prism, the quadrangular outer shell is arranged so that one side extends in the vertical direction, for example, or one corner and its corner. The other diagonal corner is arranged so as to face the horizontal direction.

According to the present invention, an underwater noise suppression structure composed of an underwater noise reflection absorption structure capable of efficiently suppressing underwater noise can be used around a point where underwater noise is generated due to construction such as pile driving and underwater noise. By installing in the direction of suppressing diffusion, underwater noise can be efficiently suppressed, diffusion of underwater noise can be suppressed, and adverse effects of underwater noise on aquatic organisms can be prevented.

1-5,7,1A Underwater noise reflection absorption structure 9A-9E Underwater noise reflection absorption structure 10A, 10B Underwater noise reflection absorption structure 1a-5a, 7a Outer shell 1b-5b, 7b Internal cavity 1c, 2c, 4c, 7c, 7d Sound incident surface 11-27, 11A Underwater noise suppression structure 31 Gas 32,33 Filling material 34 Muddy water 35-37 Porous sound absorbing material 35a-37a Pyramid-shaped protrusion 40 Iron plate 41-47,70 Underwater Noise suppression structures 41a, 47a Open portions 42a to 45a Open portions 41A, 41B, 42A, 42B Underwater noise suppression structure 50 Underwater noise generation point 51 Submarine type underwater noise suppression structure a Incident wave b, d Reflected wave c , E Transmitted wave Z Width of underwater noise reflection absorption structure

Claims (16)

An underwater noise reflection absorption structure for suppressing underwater noise.
Underwater noise is reflected on the sound incident surface,
An underwater noise reflection / absorption structure configured to absorb or reflect noise or resonate with noise inside the underwater noise reflection / absorption structure. The underwater noise reflection absorbing structure according to claim 1, wherein the sound incident surface has a curved surface or an inclined surface. The underwater noise reflection absorption structure according to claim 1 or 2, wherein the inside thereof includes a filling material composed of at least one of a gas, a liquid having a specific gravity higher than that of water, a sound absorbing material, a reflecting material and a resonance material. An outer shell body constituting the sound incident surface and having an internal cavity is provided.
The underwater noise reflection absorption structure according to claim 3, wherein the filling material is filled in the internal cavity. The underwater noise reflection absorption structure according to claim 4, wherein the outer shell is divided. The underwater noise reflection absorption structure according to any one of claims 1 to 5, which is entirely formed in a columnar shape. The underwater noise reflection absorption structure according to any one of claims 1 to 5, which is entirely formed in a plate shape. An underwater noise suppression structure including the underwater noise reflection absorption structure according to any one of claims 1 to 7. The underwater noise suppression structure including the underwater noise reflection / absorption structure configured in the columnar according to claim 6, wherein a plurality of underwater noise reflection / absorption structures configured in the columnar column are arranged in the vertical direction and submerged in water. Suspended underwater noise suppression structure. The underwater noise suppression structure including the underwater noise reflection / absorption structure configured in the columnar according to claim 6, wherein a plurality of underwater noise reflection / absorption structures configured in the columnar column are arranged in the horizontal direction and submerged in water. Hanging underwater noise suppression structure. Of the plurality of underwater noise reflection and absorption structures arranged in the horizontal direction, the lower underwater noise reflection and absorption structure was filled with muddy water, and the inside of the underwater noise reflection and absorption structure near the water surface was filled with gas. The underwater noise suppression structure according to claim 10. The underwater noise suppression structure according to any one of claims 8 to 11, wherein an iron plate is arranged on a sound emitting surface on the back surface side of the sound incident surface of the underwater noise reflection absorbing structure. The underwater noise suppression structure according to any one of claims 8 to 12, which is configured to be movable in water by a ship. One of claims 8 to 13 in which a plurality of the underwater noise reflection absorption structures are suspended in water, surrounding the underwater noise generation point when viewed from above, or approaching the generation point and partially opening the structure. The underwater noise suppression structure described in. The underwater noise reflection absorption structure according to any one of claims 1 to 7 or the underwater noise suppression structure according to any one of claims 8 to 14 is placed around a point where underwater noise is generated and / or in the water. An underwater noise suppression method that suppresses underwater noise by installing it in a direction that suppresses the diffusion of noise. The underwater noise suppression method according to claim 15, wherein the underwater noise reflection absorption structure or the underwater noise suppression structure is installed so as to overlap in the incident direction of the underwater noise.

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