Surface material

Abstract

To provide a surface material of an underwater structure, which can reduce an amount of sound waves returning to a generation source.SOLUTION: A surface material according to one embodiment of the present disclosure forms a surface part of an underwater structure, and includes: a sound absorption layer which is positioned in an outermost portion of the surface material and absorbs a sound wave; and a reflection layer which is positioned inside the sound absorption layer of the surface material and reflects the sound wave transmitting through the sound absorption layer at a reflection angle different from an incident angle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to surfacing for underwater structures. [Background technology]

[0002] Patent Document 1 listed below discloses an underwater sound-absorbing material made by laminating rubber sheets having a large number of pores. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-227702 Summary of the Invention [Problem to be solved by the invention]

[0004] Underwater structures can absorb sound waves emitted from, for example, a construction site by providing sound-absorbing material on their surface. However, it is virtually impossible for the sound-absorbing material to absorb all sound waves that reach the underwater structure. Therefore, sound waves reflected by the underwater structure may return to the source of the sound waves as noise.

[0005] Therefore, an object of the present disclosure is to provide a surface material for an underwater structure that can reduce the amount of sound waves that return to the source. [Means for solving the problem]

[0006] A surface material according to one aspect of the present disclosure is a surface material that forms the surface portion of an underwater structure, and includes an acoustic absorption layer located in the outermost part of the surface material and absorbing sound waves, and a reflective layer located in a part of the surface material that is more inward than the acoustic absorption layer and reflects sound waves that have passed through the acoustic absorption layer at a reflection angle different from the angle of incidence. [Effects of the Invention]

[0007] This configuration makes it possible to provide a surface material for an underwater structure that can reduce the amount of sound waves that return to the source of the sound. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a surface material according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of a surface material according to a first modification of the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view of a surface material according to a second modification of the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a surface material according to a third modification of the first embodiment. [Figure 5] FIG. 5 is a cross-sectional view of a surface material according to the second embodiment. [Figure 6] FIG. 6 is a cross-sectional view of a surface material according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) The following describes the embodiments. First, a surface material 100 according to the first embodiment will be described. FIG. 1 is a cross-sectional view of the surface material 100 according to the first embodiment. The vertical direction of the paper in FIG. 1 is the thickness direction of the surface material 100. The surface material 100 forms the surface portion of an underwater structure 101 located underwater. Examples of the underwater structure 101 include buildings located underwater and ships that navigate on or underwater. Furthermore, in this embodiment, "water" includes both "seawater" and "freshwater."

[0010] In this embodiment, the surface material 100 is attached to the surface of the main body 102 of the underwater structure 101. However, the surface material 100 may be formed integrally with the main body 102 of the underwater structure 101. Furthermore, the surface material 100 may be formed from multiple panels or from a single panel. Hereinafter, the water side of the surface material 100 will be referred to as the "outside" and the main body 102 side will be referred to as the "inside". In Figure 1, the top side of the paper is the outside and the bottom side of the paper is the inside. Furthermore, the outside surface will be referred to as the "front surface" and the inside surface will be referred to as the "back surface".

[0011] As shown in Fig. 1, the surface material 100 according to this embodiment includes a sound absorbing layer 10 and a reflective layer 20. These components will be described below in order.

[0012] <Sound absorbing layer> The sound absorbing layer 10 is a layer that absorbs sound waves. The sound absorbing layer 10 is located at the outermost part of the facing material 100. Therefore, the surface of the sound absorbing layer 10 comes into contact with water. Furthermore, the sound absorbing layer 10 of this embodiment has a smooth surface. Therefore, water around the underwater structure 101 flows smoothly along the surface of the underwater structure 101, and turbulence is unlikely to occur. For example, if the underwater structure 101 is a ship, the smooth surface of the sound absorbing layer 10 can reduce the resistance that the underwater structure 101 experiences from the water.

[0013] Suppose there is a sound source outside the underwater structure 101 that generates sound waves, for example, during construction work, and the sound waves emitted from the sound source travel underwater and reach the underwater structure 101. In this case, the sound waves pass through the sound-absorbing layer 10, and a portion of them is absorbed by the sound-absorbing layer 10. Generally, the ease with which sound waves pass through a medium, that is, the ease with which sound waves are reflected by a medium, depends on the acoustic impedance of the medium. In the example of this embodiment, if the difference in acoustic impedance between water and the sound-absorbing layer 10 is small, sound waves that have passed through the water will easily pass through the sound-absorbing layer 10, and if the difference in acoustic impedance between water and the sound-absorbing layer 10 is large, sound waves that have passed through the water will have difficulty passing through the sound-absorbing layer 10. Note that acoustic impedance is a numerical representation of the ease with which sound propagates, and is the product of the density of the medium and the speed of sound in the medium.

[0014] Here, the material of the sound absorbing layer 10 is not limited, but the sound absorbing layer 10 of this embodiment may be made primarily of, for example, rubber, urethane resin, or acrylic resin, and may contain at least one of pores and metal material inside. By adjusting the main material of the sound absorbing layer 10, the number of pores, and the amount of metal material, it is possible to arbitrarily change the density of the sound absorbing layer 10 and the speed of sound in the sound absorbing layer 10, and to arbitrarily change the acoustic impedance. In other words, by adjusting the material, etc. of the sound absorbing layer 10, it is possible to form the sound absorbing layer 10 so that sound waves that have traveled underwater can be transmitted through it.

[0015] <Reflection layer> The reflective layer 20 is a layer that reflects sound waves that have passed through the sound absorbing layer 10. The reflective layer 20 is located in a portion of the surface material 100 that is more inward than the sound absorbing layer 10. The reflective layer 20 of this embodiment is adjacent to the sound absorbing layer 10 and has a different acoustic impedance from the sound absorbing layer 10. In this embodiment, the reflective layer 20 has a higher acoustic impedance than the sound absorbing layer 10.

[0016] As mentioned above, whether a sound wave is likely to be reflected by a medium depends on the acoustic impedance of the medium. In the example of this embodiment, if the difference in acoustic impedance between the sound absorbing layer 10 and the reflecting layer 20 is large, the sound waves that have passed through the sound absorbing layer 10 are likely to be reflected by the reflecting layer 20, and if the difference in acoustic impedance between the sound absorbing layer 10 and the reflecting layer 20 is small, the sound waves that have passed through the sound absorbing layer 10 are unlikely to be reflected by the reflecting layer 20.

[0017] The material of the reflective layer 20 is not limited, but the reflective layer 20 of this embodiment may be made primarily of, for example, rubber, urethane resin, acrylic resin, or the like, and may contain at least one of pores and a metal material inside, similar to the sound absorbing layer 10. Therefore, by adjusting the primary material of the reflective layer 20, the number of pores, and the amount of metal material, it is possible to arbitrarily change the density of the reflective layer 20 and the sound speed in the reflective layer 20, and to arbitrarily change the acoustic impedance. In other words, by adjusting the material of the reflective layer 20, etc., it is possible to form the reflective layer 20 so that sound waves that have passed through the sound absorbing layer 10 are reflected by the reflective layer 20.

[0018] Furthermore, the reflective layer 20 of this embodiment includes a plurality of reflective surface protrusions 21 on its surface. Each reflective surface protrusion 21 has an inclined surface 22 that is inclined with respect to a macroscopic surface 28 of the reflective layer 20. The macroscopic surface 28 of the reflective layer 20 is the surface of the reflective layer 20 when viewed over a wide area, and is the average plane of the surface of the reflective layer 20. In this embodiment, the macroscopic surface 28 of the reflective layer 20 is parallel to the surface of the sound absorbing layer 10 and also parallel to the surface of the main body 102 of the underwater structure 101.

[0019] The reflective layer 20 of this embodiment includes the reflective surface convex portions 21 as described above, and therefore reflects sound waves that have passed through the sound absorbing layer 10 at a reflection angle different from the angle of incidence. Note that the incident angle of the sound wave here refers to the angle between a perpendicular line to the macroscopic surface of the reflective layer 20 (hereinafter simply referred to as the "perpendicular line to the reflective layer 20") and the propagation direction of the sound wave that is incident on the reflective layer 20. Also, the reflection angle of the sound wave refers to the angle between a perpendicular line to the reflective layer 20 and the propagation direction of the sound wave reflected by the reflective layer 20.

[0020] Therefore, as shown by the dashed arrow in Fig. 1, for example, when a sound wave that has passed through the sound absorbing layer 10 is incident on the reflecting layer 20 at an incident angle of zero degrees (i.e., parallel to the normal to the reflecting layer 20), the reflecting layer 20 reflects the sound wave at a reflection angle different from zero degrees. In other words, in the example shown in Fig. 1, the sound wave reflected by the reflecting layer 20 does not return to the source of the sound wave. Therefore, the surface material 100 according to this embodiment can reduce the amount of sound wave that returns to the source.

[0021] <Modification> The reflective surface protrusions 21 shown in Fig. 1 are arranged continuously with no gaps. However, the arrangement of the reflective surface protrusions 21 is not limited to the above. For example, as shown in Fig. 2, the reflective surface protrusions 21 may be arranged at a certain distance. In other words, a flat portion 23 parallel to the macroscopic surface of the reflective layer 20 may be located between adjacent reflective surface protrusions 21.

[0022] 1 are all the same size, and the angles of the inclined surfaces 22 are all the same. However, the size of the reflective surface convex portions 21 and the angles of the inclined surfaces 22 are not limited to those described above. For example, as shown in FIG. 3, the reflective surface convex portions 21 may be different sizes, and the angles of the inclined surfaces 22 may be different.

[0023] 1 has a flat inclined surface 22. However, the shape of the inclined surface 22 is not limited to this. For example, as shown in FIG. 4, the inclined surface 22 of the reflective surface convex portion 21 may be a curved surface.

[0024] As described above, in this embodiment, the reflective layer 20 includes the reflective surface convex portions 21, so that sound waves transmitted through the sound absorbing layer 10 can be reflected at a reflection angle different from the angle of incidence. However, the reflective layer 20 does not have to be configured as described above as long as it can reflect sound waves at a reflection angle different from the angle of incidence. For example, the density of the reflective layer 20 may be made non-uniform so that sound waves can be reflected at a reflection angle different from the angle of incidence.

[0025] Furthermore, in this embodiment, the sound absorbing layer 10 and the reflecting layer 20 are adjacent to each other, but a layer other than these may be located between the sound absorbing layer 10 and the reflecting layer 20 as long as the sound waves that have passed through the sound absorbing layer 10 can be reflected at a reflection angle different from the angle of incidence.

[0026] (Second embodiment) Next, a surface material 200 according to a second embodiment will be described. Fig. 5 is a cross-sectional view of the surface material 200 according to the second embodiment. The surface material 200 according to this embodiment differs from the surface material 100 according to the first embodiment in that the reflective layer 20 does not include reflective surface convexities 21 (see Fig. 1) on the surface, but includes reflective back surface convexities 24 on the back surface. Except for this point, the configuration of the surface material 200 according to the second embodiment is basically the same as the configuration of the surface material 100 according to the first embodiment.

[0027] The surface material 200 according to the second embodiment will be described below, focusing on the shape of the reflective layer 20. Among the components of the surface material 200 according to the second embodiment, those components that are the same as or correspond to the components of the surface material 100 according to the first embodiment will be assigned the same reference numerals as in the first embodiment, and descriptions thereof will be omitted.

[0028] As shown in Fig. 5, the reflective layer 20 of this embodiment has a smooth surface that is parallel to the surface of the sound absorbing layer 10. Meanwhile, as described above, the reflective layer 20 includes a plurality of reflective back surface protrusions 24 on its back surface. Each reflective back surface protrusion 24 has an inclined surface 25 that is inclined with respect to a macroscopic back surface 29 of the reflective layer 20. The macroscopic back surface 29 of the reflective layer 20 is the back surface of the reflective layer 20 when viewed over a wide area, and is the average surface of the back surface of the reflective layer 20. In this embodiment, the macroscopic back surface 29 of the reflective layer 20 is parallel to the surface of the sound absorbing layer 10 and the surface of the reflective layer 20.

[0029] In the first embodiment, a case has been described in which sound waves that have passed through the sound absorbing layer 10 are reflected by the surface of the reflective layer 20, but depending on the inner medium, sound waves may be reflected not only by the surface but also by the back surface of the reflective layer 20. The dashed arrows in Fig. 5 indicate the propagation path of sound waves that have passed through the sound absorbing layer 10 and reach the back surface of the reflective layer 20 where they are reflected. Because the reflective layer 20 of this embodiment includes the reflective back surface convex portions 24 as described above, when sound waves that have passed through the sound absorbing layer 10 reach the back surface of the reflective layer 20, the sound waves are reflected at a reflection angle different from the angle of incidence, as shown by the dashed arrows in Fig. 5.

[0030] Therefore, in the example shown in Fig. 5, sound waves reflected on the back surface of the reflective layer 20 do not return to the source of the sound waves. Therefore, according to the surface material 200 of this embodiment, the amount of sound waves returning to the source can be reduced, similar to the surface material 100 of the first embodiment. Note that in Fig. 5, the propagation direction of the reflected sound waves changes at the boundary between the sound absorbing layer 10 and the reflective layer 20, but this is due to refraction of the sound waves.

[0031] (Third embodiment) Next, a surface material 300 according to a third embodiment will be described. Fig. 6 is a cross-sectional view of the surface material 300 according to the third embodiment. The surface material 300 according to this embodiment differs from the surface material 100 according to the first embodiment in that the sound absorbing layer 10 includes two layers with different acoustic impedances. Except for this point, the configuration of the surface material 300 according to the third embodiment is basically the same as the configuration of the surface material 100 according to the first embodiment.

[0032] The following describes the surface material 300 according to the third embodiment, focusing on the configuration of the sound absorbing layer 10. Of the components of the surface material 300 according to the third embodiment, those that are the same as or correspond to the components of the surface material 100 according to the first embodiment are given the same reference numerals as in the first embodiment, and descriptions thereof will be omitted.

[0033] As shown in Fig. 6, the sound absorbing layer 10 of this embodiment includes a first sound absorbing layer 11 and a second sound absorbing layer 12. The first sound absorbing layer 11 is located on the outer side of the sound absorbing layer 10. The surface of the first sound absorbing layer 11 corresponds to the surface of the sound absorbing layer 10 and is smooth. On the other hand, the second sound absorbing layer 12 is located on the inner side of the first sound absorbing layer 11 of the sound absorbing layer 10 and is adjacent to the first sound absorbing layer 11.

[0034] The second sound absorbing layer 12 has a different acoustic impedance from the first sound absorbing layer 11. In this embodiment, the second sound absorbing layer 12 has a higher acoustic impedance than the first sound absorbing layer 11 and a lower acoustic impedance than the reflecting layer 20. Generally, at the boundary surface between media with different acoustic impedances, sound waves that propagate at an angle to the normal to the boundary surface are refracted.

[0035] Furthermore, the second sound absorbing layer 12 includes a plurality of sound absorbing surface protrusions 13 on its surface. Each sound absorbing surface protrusion 13 has an inclined surface 14 that is inclined relative to a macroscopic surface 18 of the second sound absorbing layer 12. The macroscopic surface 18 of the second sound absorbing layer 12 refers to the surface of the second sound absorbing layer 12 when viewed over a wide area, and is the average plane of the surface of the second sound absorbing layer 12. In this embodiment, the macroscopic surface 18 of the second sound absorbing layer 12 is parallel to the surface of the first sound absorbing layer 11 and the macroscopic surface 28 of the reflective layer 20.

[0036] Because the sound absorbing layer 10 of this embodiment includes the second sound absorbing layer 12 as described above, as shown by the dashed arrow, sound waves that pass through the first sound absorbing layer 11 perpendicular to the surface of the first sound absorbing layer 11 enter the second sound absorbing layer 12 in a direction inclined with respect to the normal to the inclined surface 14 of the second sound absorbing layer 12. Furthermore, the second sound absorbing layer 12 has a different acoustic impedance from the first sound absorbing layer 11. Therefore, in the example shown in FIG. 6 , sound waves are refracted at the boundary surface between the first sound absorbing layer 11 and the second sound absorbing layer 12.

[0037] In this manner, in this embodiment, sound waves that have passed through the first sound absorbing layer 11 are refracted by the second sound absorbing layer 12 and reach the reflecting layer 20. Therefore, the propagation path of the sound waves reflected by the reflecting layer 20 is more complex than when the sound absorbing layer 10 is made up of a single layer, making it possible to further reduce the amount of sound waves that return to the source of generation.

[0038] Although the sound absorbing layer 10 of this embodiment includes two layers, the first sound absorbing layer 11 and the second sound absorbing layer 12, it may include three or more layers. Even in this case, the propagation path of the sound waves reflected by the reflective layer 20 becomes more complex than when the sound absorbing layer 10 is made up of a single layer, and the amount of sound waves returning to the source can be further reduced.

[0039] (summary) The first item disclosed in this specification is a surface material that forms the surface portion of an underwater structure, and that includes an acoustic absorption layer located in the outermost part of the surface material and absorbing sound waves, and a reflective layer located in the part of the surface material that is more inward than the acoustic absorption layer and reflects sound waves that have passed through the acoustic absorption layer at a reflection angle different from the angle of incidence.

[0040] This configuration can reduce the amount of sound waves returning to the source.

[0041] The second item disclosed in this specification is the surface material according to the first item, wherein the sound absorbing layer has a smooth surface.

[0042] With this configuration, the water around the underwater structure tends to flow smoothly along the surface of the underwater structure.

[0043] The third item disclosed in this specification is a surface material described in the first or second item, wherein the reflective layer includes a plurality of reflective surface protrusions on the surface, and each of the plurality of reflective surface protrusions has an inclined surface that is inclined with respect to the macroscopic surface of the reflective layer.

[0044] According to this configuration, the sound waves that have passed through the sound absorbing layer can be reflected by the reflective layer at a reflection angle that is different from the angle of incidence.

[0045] The fourth item disclosed in this specification is a surface material described in any one of the first to third items, wherein the reflective layer includes a plurality of reflective back surface convex portions on the back surface, and the plurality of reflective back surface convex portions each have an inclined surface that is inclined with respect to the macroscopic back surface of the reflective layer.

[0046] Even with this configuration, the sound waves that have passed through the sound absorbing layer can be reflected by the reflective layer at a reflection angle that is different from the angle of incidence.

[0047] A fifth item disclosed in this specification is a surface material according to any one of the first to fourth items, wherein the sound absorbing layer includes a first sound absorbing layer and a second sound absorbing layer located in a portion of the sound absorbing layer more inward than the first sound absorbing layer and having an acoustic impedance different from that of the first sound absorbing layer.

[0048] With this configuration, sound waves that have passed through the first sound absorbing layer are more likely to be refracted at the surface of the second sound absorbing layer, further reducing the amount of sound waves that return to the source of generation.

[0049] A sixth item disclosed in this specification is the surface material described in the fifth item, in which the second sound-absorbing layer includes a plurality of sound-absorbing surface protrusions on its surface, and each of the plurality of sound-absorbing surface protrusions has an inclined surface that is inclined with respect to the macroscopic surface of the second sound-absorbing layer.

[0050] With this configuration, sound waves that have passed through the first sound absorbing layer are more likely to be refracted at the surface of the second sound absorbing layer. [Explanation of symbols]

[0051] 10 sound absorbing layer 11 First sound-absorbing layer 12 Second sound-absorbing layer 13 Sound-absorbing surface convex part 14 Slope 18 Macroscopic Surfaces 20 reflective layer 21 Reflective surface convexity 22 Slope 23 Flat area 24 Reflective back convex part 25 Slope 28 Macroscopic Surfaces 29 Macroscopic Backside 100 Surface material 101 Underwater structures 102 Main Unit 200 Surface material 300 Surface material

Claims

1. A surface material forming a surface portion of an underwater structure, an acoustic absorption layer located on the outermost portion of the surface material and absorbing sound waves; a reflective layer located inside the sound absorbing layer of the surface material, which reflects sound waves transmitted through the sound absorbing layer at a reflection angle different from the angle of incidence.

2. The surface material according to claim 1 , wherein the sound absorbing layer has a smooth surface.

3. the reflective layer includes a plurality of reflective surface protrusions on a surface thereof; The surface material according to claim 1 , wherein the plurality of reflective surface protrusions each have an inclined surface that is inclined with respect to the macroscopic surface of the reflective layer.

4. the reflective layer includes a plurality of reflective rear surface convex portions on a rear surface, The surface material according to claim 1 , wherein the plurality of reflective back surface convex portions each have an inclined surface that is inclined with respect to the macroscopic back surface of the reflective layer.

5. The sound absorbing layer is A first sound absorbing layer; 2. The surface material according to claim 1, further comprising: a second sound absorbing layer located inside the first sound absorbing layer of the sound absorbing layer, the second sound absorbing layer having an acoustic impedance different from that of the first sound absorbing layer.

6. the second sound-absorbing layer includes a plurality of sound-absorbing surface protrusions on a surface thereof; The surface material according to claim 5 , wherein each of the plurality of sound absorbing surface projections has an inclined surface that is inclined with respect to the macroscopic surface of the second sound absorbing layer.

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