Pipe noise suppression structure

Abstract

To provide a pipe propagation sound suppression structure 1 that provides excellent noise reduction effect and easy attachment and removal of sound absorbing material 40.SOLUTION: A pipe propagation sound suppression structure 1 comprises: a tube 20 extending in a longitudinal direction D; three or more partition plates 30 protruding from an inner surface 22 of the tube 20 and spaced apart along the longitudinal direction D; a sound absorbing material 40 extending from a free end 34 of one partition plate 30 to a free end 34 of the other adjacent partition plate 30; and an air layer 50 provided between the sound absorbing material 40 and the inner surface 22. The partition plates 30 are arranged respectively intersecting the longitudinal direction D. Each of the adjacent partition plates 30 has a notch 36 formed in the free end 34. One partition plate 30 has a positioning portion 38 protruding toward the other partition plate 30. The positioning portion 38 contacts the sound absorbing material 40 and restricts movement of the sound absorbing material 40 toward the inner surface 22 side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a structure for suppressing noise propagating in a pipe. [Background technology]

[0002] Conventional sound reduction devices that use phase interference and resonators can only reduce specific low-frequency sounds at pinpoint accuracy, and are unable to reduce low-frequency sounds over a wide range, meaning they cannot reduce sounds such as blasting noise during tunnel excavation.

[0003] Therefore, a sound reduction device has been proposed that can significantly reduce propagating sound in a desired frequency range over a wide range by providing an acoustic absorption layer on the edge of a partition plate that is aligned in a direction that intersects with the propagation direction of the propagating sound, thereby converting vibration energy based on particle velocity near the edge into thermal energy (Patent Document 1).

[0004] This sound reduction device utilizes the phenomenon that when there is an array of multiple appropriately sized depressions separated by partitions or the like perpendicular to the propagation direction, areas of high particle velocity appear concentrated in the normal direction of the opening surfaces near the partitions that form the opening surfaces of the depressions, and converts sound energy into thermal energy by providing a sound-absorbing layer in the area where this increase in particle velocity is concentrated.

[0005] This noise reduction device is called an in-pipe sound propagation suppression structure because it is useful not only for blasting noise during tunnel construction as mentioned above, but also for sound that propagates through ducts installed in the ceiling of an office building or in the air.

[0006] Furthermore, an in-pipe sound propagation suppression structure has also been proposed that improves on this type of in-pipe sound propagation suppression structure by providing sound-absorbing material between the partition plates to obtain an excellent noise reduction effect (Patent Document 2). The in-pipe sound propagation suppression structure of Patent Document 2 comprises a sound-absorbing structure that uses air column resonance between the partition plates, a sound-absorbing structure that uses porous sound-absorbing material, and the sound-absorbing structure that uses the edge effect of Patent Document 1. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-207385 [Patent Document 2] Patent Publication No. 2021-196388 Summary of the Invention [Problem to be solved by the invention]

[0008] However, further improvements are required for practical application of conventional structures for suppressing noise transmitted within pipes, which have sound-absorbing materials between partition plates.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a structure for suppressing noise propagating inside a pipe, which can obtain an excellent noise reduction effect and in which the sound-absorbing material can be easily attached and detached. [Means for solving the problem]

[0010] The present invention has been made to solve at least some of the above-mentioned problems, and can be realized as the following aspects or application examples.

[0011] [1] One aspect of the pipe propagation sound suppression structure according to the present invention is as follows: A pipe-in-pipe sound-propagation suppression structure having a pipe body extending in a longitudinal direction, three or more partition plates protruding from an inner peripheral surface of the pipe body and arranged at intervals along the longitudinal direction, sound-absorbing materials extending from a free end of one of the adjacent partition plates to a free end of the other of the adjacent partition plates, and an air layer provided between the sound-absorbing materials and the inner peripheral surface, The partition plates are arranged to intersect with the longitudinal direction, Each of the adjacent partition plates has a notch formed at the free end, one of the partition plates has a positioning portion that protrudes toward the other of the partition plates, The positioning portion is in contact with the sound absorbing material to restrict movement of the sound absorbing material toward the inner peripheral surface.

[0012] [2] In one aspect of the above-mentioned pipe propagation sound suppression structure, The tube has a rectangular cross section, The partition plate has an outer edge that contacts the inner circumferential surface and the free end that forms a rectangular opening edge at a center, At least one notch and one positioning portion may be formed on each side of the opening edge.

[0013] [3] In one aspect of the above-mentioned pipe propagation sound suppression structure, The positioning portion may extend from the one partition plate to the other partition plate.

[0014] [4] In one aspect of the above-mentioned pipe propagation sound suppression structure, In any one of claims 1 to 3, At least one of the one partition plate and the other partition plate may further have a claw portion that protrudes toward the inside of the sound-absorbing material. [Effects of the Invention]

[0015] The in-pipe sound-transmission suppression structure according to the present invention provides an excellent noise reduction effect and allows the sound-absorbing material to be easily attached and detached. [Brief explanation of the drawings]

[0016] [Figure 1] 2 is a cross-sectional view taken along the line AA of the in-pipe sound propagation suppression structure according to the present embodiment. FIG. [Figure 2] 1A is a BB cross-sectional view of the in-pipe sound-propagation suppression structure according to this embodiment, and FIG. 1B is a CC cross-sectional view of the in-pipe sound-propagation suppression structure according to this embodiment. [Figure 3] 2 is an enlarged perspective view showing a part of the CC cross section of the in-pipe sound-propagation suppression structure according to the present embodiment. FIG. [Figure 4] FIG. 2 is a diagram illustrating measurement of sound pressure levels using test specimens of Example 1 and Comparative Example 1. [Figure 5]FIG. 10 is a longitudinal sectional view illustrating the measurement of sound pressure levels using test specimens of Comparative Examples 2 and 3. [Figure 6] 1 is a graph showing the noise reduction effects of Example 1 and Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0017] Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Note that the embodiments described below do not unduly limit the content of the present invention as defined in the claims. Furthermore, not all of the configurations described below are necessarily essential components of the present invention.

[0018] 1. Structure for suppressing noise transmitted through pipes The in-pipe sound propagation suppression structure 1 according to this embodiment will be described using Figures 1 to 3. Figure 1 is an AA cross section in (a) of Figure 2, which explains the in-pipe sound propagation suppression structure 1 according to this embodiment, Figure 2(a) is a BB cross section of the in-pipe sound propagation suppression structure 1 in Figure 1, (b) is a CC cross section of the in-pipe sound propagation suppression structure 1, and Figure 3 is an enlarged perspective view showing a part of the CC cross section of the in-pipe sound propagation suppression structure 1 according to this embodiment. Note that Figure 3 shows the process of inserting sound-absorbing material 40 between partition plates 30.

[0019] The pipe-introducing sound suppression structure 1 shown in Figures 1 to 3 comprises a pipe body 20 extending in a longitudinal direction D, three or more partition plates 30 protruding from an inner surface 22 of the pipe body 20 and arranged at intervals along the longitudinal direction D, a sound-absorbing material 40 extending from a free end 34 of one adjacent partition plate 30 to the free end 34 of the other partition plate 30, and an air layer 50 provided between the sound-absorbing material 40 and the inner surface 22.

[0020] The pipe-inside sound propagation suppression structure 1 in Fig. 1 has four air layers 50, for example, with four sound-absorbing materials 40 arranged between five partition plates 30 on the inner peripheral surface 22 of the pipe body 20 along the longitudinal direction D of the pipe body 20. The number of partition plates 30 in the pipe-inside sound propagation suppression structure 1 can be increased or decreased depending on the required suppression effect of the propagated sound.

[0021] The pipe-borne sound suppression structure 1 is a tubular structure extending along a central axis O that opens at both ends with a first opening 24 and a second opening 26. The pipe-borne sound suppression structure 1 can be connected to another pipe at the first opening 24 and the second opening 26 to form part of a continuous tubular structure. The central axis O is an imaginary axis line that runs through the center of the pipe 20 and is along the longitudinal direction D. The central axis O also runs along the sound propagation direction in the pipe-borne sound suppression structure 1, and is parallel to the X direction in the figure.

[0022] The in-pipe sound-propagation suppression structure 1 is, for example, a part of a duct installed in a building. The in-pipe sound-propagation suppression structure 1 has a rectangular cylindrical shape ( FIG. 2 ) when viewed along the longitudinal direction D, but is not limited to this and may have a cylindrical shape of a polygon other than a rectangle, or a circular or semicircular shape. When the pipe body 20 is a duct, the pipe body 20 may be made of a material such as a metal, such as a galvanized iron plate, a galvalume steel plate (registered trademark), or a stainless steel plate, or a synthetic resin, such as rigid polyvinyl chloride.

[0023] The pipe 20 has the same pipe diameter in the longitudinal direction D, but may be configured with a plurality of different pipe diameters. The pipe 20 may also have a bent portion. Even when the pipe 20 is bent, the longitudinal direction D is the longitudinal direction of the range of the pipe 20 in which the partition plate 30 is arranged.

[0024] The pipe-propagated sound suppression structure 1 can be used in, for example, tunnels, offices, hospitals, schools, factories, and the like.

[0025] 2. Sound-absorbing material The sound-absorbing material 40 is provided at the free ends 34 of the partition plates 30, and has a width (length in the X-axis direction) extending from the free end 34 of one adjacent partition plate 30 to the free end 34 of the other partition plate 30. The length (length in the Z-axis direction) of the sound-absorbing material 40 is preferably at least equal to or greater than the length of the free ends 34 of the partition plates 30, in order to efficiently convert sound energy into thermal energy at the free ends 34 of the partition plates 30. The thickness (length in the Y-axis direction) of the sound-absorbing material 40 can be set depending on the sound-propagation suppression effect, ease of handling, the maximum diameter of the in-pipe sound-propagation suppression structure 1, and the equipment cost, for example, and can be between 12 mm and 100 mm, and preferably between 25 mm and 50 mm.

[0026] The sound-absorbing material 40 is arranged so as to cover the gap between two adjacent partition plates 30 protruding from the inner circumferential surface 22. Therefore, in the example of FIG. 2, the sound-absorbing material 40 is arranged in a ring shape along the opening edge 35 formed by the free ends 34 of the partition plates 30, and a ring-shaped air layer 50 is formed along the outer periphery of the sound-absorbing material 40. The sound-absorbing material 40 is installed flush with the free ends 34, but may protrude slightly from the free ends 34. The sound-absorbing material 40 is arranged at a predetermined distance (the height of the air layer 50) from the inner circumferential surface 22. When the sound-absorbing material 40 is arranged along the rectangular opening edge 35, the sound-absorbing material 40 can be formed in a ring shape by arranging four square pillar-shaped sound-absorbing materials 40 so that the ends of adjacent sound-absorbing materials 40 overlap, as shown in FIG. 2(b).

[0027] The sound-absorbing material 40 can be made of any material commonly used for sound-absorbing materials, such as porous materials such as glass wool, rock wool, metal fiber material, and activated carbon. The provision of porous sound-absorbing material 40 provides excellent noise reduction effects, primarily for frequencies above 800 Hz. Glass wool is preferred as the sound-absorbing material 40 because of its price and ease of handling.

[0028] 3. Air layer An air layer 50 is formed between two adjacent partition plates 30, between the sound-absorbing material 40 and the inner peripheral surface 22. The partition plates 30, which have a predetermined height and spacing, utilize the air layer 50 to obtain a noise reduction effect due to air column resonance mainly between 200 Hz and 800 Hz.

[0029] 4. Divider The partition plates 30 protrude from the inner peripheral surface 22 of the pipe body 20 and are arranged at intervals on the inner peripheral surface 22 along the longitudinal direction D. At least three partition plates 30 are provided in the pipe-in-pipe sound propagation suppression structure 1. The number of partition plates 30 can be set according to the required sound propagation suppression effect. A noise reduction effect due to air column resonance can be obtained between adjacent partition plates 30, so a larger number of partition plates 30 is preferable. The noise reduction effect due to air column resonance of partition plates 30 with a specified height and spacing is obtained mainly between 200 Hz and 800 Hz.

[0030] The multiple partition plates 30 are each arranged so as to intersect with the longitudinal direction D. To efficiently suppress propagated sound, the partition plates 30 are preferably arranged so as to be perpendicular to the longitudinal direction D. The height of each partition plate 30 is the height from the inner circumferential surface 22 to the free end 34, and can be set depending on the diameter of the tubular body 20 and the desired effect of suppressing propagated sound, but is, for example, 100 mm to 400 mm. The material of the partition plates 30 can be any material commonly used as a sound-insulating material, such as metal, glass, resin, or wood.

[0031] Each of adjacent partition plates 30 has a cutout 36 formed in its free end 34. The cutout 36 is recessed toward the inner circumferential surface 22 relative to the other free ends 34, and the sound-absorbing material 40 is exposed at the cutout 36 when viewed from the longitudinal direction D. The sound-absorbing material 40 installed between the partition plates 30 can be grasped by inserting a finger into the cutout 36, facilitating removal of the sound-absorbing material 40 during maintenance work. A gripping tool may be used instead of fingers as long as it can grasp the sound-absorbing material 40. By providing the cutouts 36 at opposing positions on adjacent partition plates 30, the sound-absorbing material 40 can be grasped by pinching it. The width of the cutout 36 along the free end 34 needs only to be wide enough to grasp the sound-absorbing material 40, and may be, for example, 10 mm to 50 mm. The height of the notch 36 (depth from the free end 34) is preferably at least 20 mm or more, so that a finger can rest on it, and is at least less than the thickness of the sound-absorbing material 40. Furthermore, as is clear from the experimental results described below, the presence or absence of the notch 36 in the in-pipe sound-propagation suppression structure 1 does not affect the noise reduction effect.

[0032] One of the partition plates 30 has a positioning portion 38 that protrudes toward the other adjacent partition plate 30. The positioning portion 38 comes into contact with the sound absorbing material 40 and moves the sound absorbing material 40 toward the inner peripheral surface 22. The positioning portion 38 is positioned from the free end 34 toward the inner circumferential surface 22 by the thickness of the sound-absorbing material 40. Preferably, the positioning portion 38 extends from one adjacent partition plate 30 to the other adjacent partition plate 30. The positioning portion 38 extending between adjacent partition plates 30 keeps the spacing between adjacent partition plates 30 constant even on the free end 34 side, facilitating insertion and removal of the sound-absorbing material 40. The shape, size, and protrusion amount of the positioning portion 38 from the partition plate 30 are not limited as long as they can restrict the sound-absorbing material 40 from moving toward the inner circumferential surface 22. For example, the positioning portion 38 may be long enough not to reach the adjacent partition plate 30. The positioning portion 38 shown in the example in FIG. 1 is a plate-like body with an L-shaped cross section, having a surface that is fixed to the partition plate 30 on the left side of the figure and a surface that contacts the sound-absorbing material 40. For the sake of stability of the sound-absorbing material 40, it is preferable that the positioning portion 38 be plate-shaped with a flat surface that comes into contact with the sound-absorbing material 40, but this is not a limitation and it may be rod-shaped. The width of the partition plate 30 (the width that comes into contact with the sound-absorbing material 40) is not particularly limited, but can be, for example, 10 mm or more and 50 mm or less. The material of the positioning portion 38 can be any material that can be used for the partition plate 30. Furthermore, as is clear from the experimental results described below, the presence or absence of the positioning portion 38 in the in-pipe sound-propagation suppression structure 1 does not affect the noise reduction effect.

[0033] As shown in FIG. 2 , the partition plate 30 has an outer edge 32 that contacts the inner circumferential surface 22 and a free end 34 that forms a rectangular opening edge 35 at the center. The outer edge 32 may be formed integrally with the inner circumferential surface 22, or the outer edge 32 and the inner circumferential surface 22 may be partially joined at multiple locations as long as the entire outer edge 32 contacts the inner circumferential surface 22. When viewed along the longitudinal direction D, the partition plate 30 has a central opening edge 35 that is annular ( FIG. 2( a) ). The term "annular" does not necessarily refer to the shape of the central opening edge 35 or the shape of the outer edge 32, but also refers to a shape that is continuous around the central opening when viewed along the longitudinal direction D as shown in FIG. 2( a). For example, this includes a partition plate 30 in which the opening edge 35 and the outer edge 32 of the partition plate 30 are annular so that they together form the sides of a rectangle, as in this embodiment, and also includes a partition plate in which the opening edge 35 and the outer edge 32 are annular, such as a circle or a polygonal ring shape other than a rectangle. The shape of the opening edge 35 at the center of the partition plate 30 is preferably similar to the shape of the inner peripheral surface 22 (outer edge 32) as shown in FIG.

[0034] The tube 20 shown in the example of FIG. 2 can have, for example, a rectangular cross section. Each of the partition plates 30 is formed to protrude from the inner circumferential surface 22 on each of the four sides, thereby achieving noise reduction effects on each of the four inner circumferential surfaces 22. At least one notch 36 and positioning portion 38 is preferably formed on each side of the opening edge 35, for example, two are formed at intervals on each side. As shown in FIG. 2(b), one rectangular columnar sound-absorbing material 40 is disposed on each side of the rectangular opening edge 35. Therefore, as shown in FIG. 2(a), if there is at least one notch 36 on each side, each sound-absorbing material 40 can be removed. Furthermore, if there is at least one positioning portion 38 on each side, each sound-absorbing material 40 can be positioned. It is more preferable to have two or more positioning portions 38 on each side to stabilize the sound-absorbing material 40.

[0035] In addition, although the noise reduction effect of the partition plate 30 is lower than that of an annular shape, it may be formed so as to protrude from one side of the inner peripheral surface 22 of the rectangular cross section toward the central axis O, and may not be provided on the other three sides.

[0036] As shown in Figures 1 and 3, in the pipe-transmitting sound suppression structure 1, at least one of the adjacent partition plates 30 and the other partition plate 30 can further have claw portions 39 that protrude toward the inside of the sound-absorbing material 40. By having the claw portions 39, the sound-absorbing material 40 can be securely held between the adjacent partition plates 30. The claw portions 39 are of a size that can dig into the side of the sound-absorbing material 40 between the adjacent partition plates 30 and into the inside of the sound-absorbing material 40, preventing the sound-absorbing material 40 from falling out from the free end 34 to the outside. The claw portions 39 are, for example, thin plate-like so as to easily dig into the inside of the sound-absorbing material 40. The claw portions 39 are formed on the rectangular opening edge It is preferable that there is at least one on each side of the sound absorbing material 35, and it is even more preferable that there are two or more on each side to stabilize the sound absorbing material 40.

[0037] The tabs 39 can be provided at the positions of the notches 36 of the partition plates 30, for example, at the lower ends of the notches 36. The positions of the notches 36 allow the sound-absorbing material 40 to be inserted between the two partition plates 30 (insertion direction I) while compressing the sound-absorbing material 40 with fingers as indicated by the arrows (compression direction P) in FIG. 3 . This allows the sound-absorbing material 40 to be pushed in until it contacts the positioning portions 38 while reducing interference with the tabs 39. The tabs 39 can be provided corresponding to each of the notches 36. The width of the tabs 39 is narrower than the width of the notches 36. When the partition plates 30 are made of a thin metal plate, when a portion on the free end 34 side is removed to form the notches 36, the portion may be removed to leave a size large enough for the tabs 39, and the remaining portion may be bent to form the tabs 39. Alternatively, the tabs 39 may protrude from both sides of adjacent partition plates 30 toward the sound-absorbing material 40 between them. The claw portion 39 can prevent the sound-absorbing material 40 from falling off the free end 34 side and can also restrict the sound-absorbing material 40 from moving toward the inner surface 22 side, so the claw portion 39 can also be used as the positioning portion 38.

[0038] 5. Inserting sound-absorbing material The insertion of the sound-absorbing material 40 will be explained using Figure 3. In Figure 3, the partition plate 30 on the front side of the figure is omitted, and a portion of the three partition plates 30 is shown enlarged. The sound-absorbing material 40 is inserted in a predetermined position between the two partition plates 30 on the back side of the figure. The bottom surface of the sound-absorbing material 40 is placed on the top surface of the positioning portion 38 shown by the dotted line, and the top surface of the sound-absorbing material 40 is flush with the free end 34 of the partition plate 30. The sound-absorbing material 40 is inserted between the partition plates 30, exposing its top surface, and also exposing part of its side surface at the cutout portion 36.

[0039] The front side of Figure 3 shows the state before the sound-absorbing material 40 is inserted between the two partition plates 30 from above. The sound-absorbing material 40 has a rectangular prism shape that is long in the Z direction. The sound-absorbing material 40 is moved downward along the insertion direction I while being crushed with fingers in the compression direction P on the side surfaces corresponding to the two cutouts 36. Because the side surfaces of the sound-absorbing material 40 are compressed and deformed, the sound-absorbing material 40 can be inserted between the two partition plates 30 while avoiding the claws 39 that protrude from the lower ends of the cutouts 36 along the X axis. The sound-absorbing material 40 is lowered until its bottom surface abuts the top surface of the positioning portion 38, and is placed in the specified position. When the fingers holding the sound-absorbing material 40 are released in this state, the material returns to its original shape, and the claws 39 pierce the side surfaces of the sound-absorbing material 40, securing the sound-absorbing material 40 to the partition plate 30. The state in which the sound-absorbing material 40 is secured is shown in the back side of the figure. In order to clearly show the shape of the positioning portion 38, the positioning portion 38 fixed to the partition plate 30 on the nearest side is shown by a solid line. [Example]

[0040] [Test specimen] Test specimens 1a and 1b will be described with reference to Figures 4 and 5. Figure 4 is a vertical cross-sectional view illustrating the measurement of sound pressure levels using test specimens 1a of Example 1 and Comparative Example 1, and Figure 5 is a vertical cross-sectional view illustrating the measurement of sound pressure levels using test specimens 1b of Comparative Examples 2 and 3. Note that in Figures 4 and 5, the same components as in Figure 1 are designated by the same reference numerals, and the notch portion 36, positioning portion 38, and claw portion 39 are omitted.

[0041] FIG. 4 shows the test specimen 1a of Example 1 and Comparative Example 1, which was installed in a sound pressure level measuring device. The test specimen 1a used a 1000 mm high vinyl chloride pipe body 20 having ten partition plates 30. The test specimen 1a had a structure in which ten 5 mm thick partition plates 30 were arranged at 50 mm intervals from a position 250 mm from the first opening 24 at the bottom end to a position 750 mm above along the X axis, and a sound absorbing material 40 with a width of 50 mm was fixed between adjacent partition plates 30, resulting in nine air layers 50 lined up along the longitudinal direction D. The height from the inner peripheral surface 22 of the partition plates 30 (the distance from the outer edge 32 to the free end 34) was 125 mm, and the air gap formed by the free end 34 was 125 mm. The square opening had a side length of 250 mm. The sound absorbing material 40 was a square pillar with a width (length along the longitudinal direction D) of 50 mm and a thickness of 50 mm, a length along the free end 34 of 300 mm, and was made of glass wool (32 kg / m 3 The height of the air layer 50 from the inner circumferential surface 22 was 75 mm.

[0042] The specimen 1a of Example 1 had three notched portions 36, each 40 mm wide and 25 mm deep (not shown), formed at 40 mm intervals on each side, and three positioning portions 38, each 40 mm wide, formed at 40 mm intervals at a position 50 mm deep from the free end 34. The specimen 1a of Comparative Example 1 did not have the notched portions 36 or the positioning portions 38.

[0043] 5 shows the test specimen 1b of Comparative Examples 2 and 3. The test specimen 1b of Comparative Example 2 is the test specimen 1a of Example 1 from which the sound-absorbing material 40 has been removed, and the test specimen 1b of Comparative Example 3 is the test specimen 1a of Comparative Example 1 from which the sound-absorbing material 40 has been removed.

[0044] [Sound pressure level measurement] Test specimens 1a and 1b were placed with the first opening 24 facing downwards as shown in Figures 4 and 5, and the sound pressure level (dB) of each was measured. In Figures 4 and 5, test specimens 1a and 1b were placed on a plywood board 4 with an opening at the center, and a speaker 6 was placed so as to cover the opening of the plywood board 4. A buffer material 5 was provided between the plywood board 4 and the speaker 6. The speaker 6 was made of a material from WASEDA An EEW-3232 flat speaker (300 x 300 mm) was used. Pink noise was used as the test sound, and the input voltage was kept constant regardless of the measurement conditions. The test specimens 1a and 1b were placed with the first opening 24 on the plywood 4 so that the sound propagation direction passed through the central axis O of the test specimens 1a and 1b. The distance between the center of the second opening 26 and the measurement point 7 was 500 mm. The devices shown in Figures 4 and 5 were placed in an anechoic chamber.

[0045] First, a 1000 mm high standard vinyl chloride square tubular body with a 500 mm square opening and no partition plate 30 or sound-absorbing material 40 (not shown) was placed in the device, and the standard sound pressure level at measurement point 7 was measured while emitting test sounds from speaker 6. Next, the standard tubular body was replaced with test bodies 1a and 1b shown in Figures 4 and 5, and the sound pressure levels of each were measured in the same way and compared with the sound pressure level of the standard tubular body.

[0046] Fig. 6 is a diagram showing the noise reduction effect of Example 1 and Comparative Examples 1 to 3. In Fig. 6, the horizontal axis represents frequency (Hz), and the vertical axis represents the noise reduction effect (dB) that indicates the amount of reduction in the sound pressure levels of test specimens 1a and 1b relative to the reference sound pressure level.

[0047] 6, it was confirmed that the test piece 1a (●) of Example 1 had a noise reduction effect at all frequencies that was almost the same as that of the test piece 1a (▲) of Comparative Example 1. Therefore, it was found that the presence or absence of the notch portion 36 and the positioning portion 38 in the partition plate 30 did not affect the noise reduction effect.

[0048] Furthermore, the noise reduction effect around 500 Hz was greater for specimen 1b (△) of comparative example 3 than for specimen 1b (◯) of comparative example 2. Therefore, it was found that without the sound-absorbing material 40, the presence of the notch 36 and the positioning portion 38 in the partition plate 30 would affect the noise reduction effect due to air column resonance.

[0049] The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects). The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. The present invention also includes configurations that have the same operational effects or achieve the same purpose as the configurations described in the embodiments. The present invention also includes a configuration in which publicly known technology is added to the configuration described in the embodiment. [Explanation of symbols]

[0050] 1...pipe-transmitted sound suppression structure, 1a, 1b...test specimen, 4...plywood, 5...buffer material, 6...speaker, 7...measurement point, 20...pipe body, 22...inner peripheral surface, 24...first opening, 26...second opening, 30...partition plate, 32...outer edge, 34...free end, 35...opening edge, 36...notch portion, 38...positioning portion, 39...claw portion, 40...sound-absorbing material, 50...air layer, D...longitudinal direction, I...insertion direction, O...central axis, P...compression direction

Claims

1. A pipe-in-pipe sound-propagation suppression structure having a pipe body extending in a longitudinal direction, three or more partition plates protruding from an inner peripheral surface of the pipe body and arranged at intervals along the longitudinal direction, sound-absorbing materials extending from a free end of one of the adjacent partition plates to a free end of the other of the adjacent partition plates, and an air layer provided between the sound-absorbing materials and the inner peripheral surface, The partition plates are arranged to intersect with the longitudinal direction, Each of the adjacent partition plates has a notch formed at the free end, one of the partition plates has a positioning portion that protrudes toward the other of the partition plates, The structure for suppressing sound propagation in a pipe, characterized in that the positioning portion contacts the sound-absorbing material to restrict movement of the sound-absorbing material toward the inner surface.

2. In claim 1, The tube has a rectangular cross section, The partition plate has an outer edge that contacts the inner circumferential surface and the free end that forms a rectangular opening edge at a center, The structure for suppressing sound propagation in a pipe, wherein at least one notch and one positioning portion are formed on each side of the opening edge.

3. In claim 1 or claim 2, The positioning portion extends from one of the partition plates to the other of the partition plates.

4. In any one of claims 1 to 3, An in-pipe sound-transmission suppression structure, characterized in that at least one of the one partition plate and the other partition plate further has a claw portion that protrudes toward the inside of the sound-absorbing material.

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