Structure for suppressing noise transmitted through pipes

Abstract

To provide an intratubular propagation sound reducing structure that offers an excellent noise reduction effect and enables cost reduction.SOLUTION: An intratubular propagation sound reducing structure 2 according to the present invention including a tube body 20 and three or more partition plates 300 fixed to an inner surface of the tube body 20 and arranged at an interval in a longitudinal direction D of the tube body 20, includes: a first structure 11 having a sound absorbing material 400 extending from a free end 340 of one of adjacent partition plates 300 to the free end 340 of the other partition plate 300 and an air layer 50 provided between the sound absorbing material 400 and an inner surface 22; and a second structure 12 that is open on the free end 340 side of the adjacent partition plates 300. The partition plates 300 are each arranged to cross the longitudinal direction D, and the partition plates 300 are arranged annularly as seen in the longitudinal direction D.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

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

[0003] Therefore, a sound reduction device has been proposed that can significantly reduce the propagating sound in the 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 intersecting 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 has an arrangement of multiple appropriately sized depressions separated by partitions or the like perpendicular to the direction of propagation. Areas of high particle velocity are concentrated in the normal direction of the opening surfaces near the partitions that form the opening surfaces of the depressions. By providing a sound absorbing layer in the area where this increase in particle velocity is concentrated, sound energy is converted into thermal energy.

[0005] This sound reduction device is useful not only for blasting noise from tunnel construction, but also for sound that propagates through ducts installed in the ceiling of an office building or in the air, and is therefore referred to as an in-pipe sound suppression structure. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-207385 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, further improvements are required for conventional structures for suppressing noise transmitted within pipes.

[0008] Therefore, an object of the present invention is to provide a structure for suppressing sound propagation in a pipe, which can obtain an excellent noise reduction effect while enabling a reduction in cost. [Means for solving the problem]

[0009] The present invention has been made to solve at least some of the above-mentioned problems, and can be realized in the following aspects or application examples.

[0010] [1] One aspect of the in-pipe sound suppression structure according to the present invention is as follows: A pipe-transmitting sound suppression structure comprising a pipe body and three or more partition plates fixed to an inner surface of the pipe body and arranged at intervals along a longitudinal direction of the pipe body, A first structure having a sound absorbing material 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 material and the inner surface; A second structure in which the free end sides of the adjacent partition plates are open; Equipped with The partition plates are disposed so as to intersect with the longitudinal direction, and the partition plates are disposed in an annular shape when viewed from the longitudinal direction. 、 By changing one or more of the number of the first structures, the number of the second structures, the number of the first structures arranged in succession, and the number of the second structures arranged in succession, it is possible to reduce noise in a specific frequency band in accordance with the frequency characteristics of the noise source. It is characterized by: [2] Another aspect of the in-pipe sound suppression structure according to the present invention is as follows: A pipe-transmitting sound suppression structure comprising a pipe body and three or more partition plates fixed to an inner surface of the pipe body and arranged at intervals along a longitudinal direction of the pipe body, A first structure having a sound absorbing material 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 material and the inner surface; A second structure in which the free end sides of the adjacent partition plates are open; Equipped with The partition plates are disposed so as to intersect with the longitudinal direction, and the partition plates are disposed in an annular shape as viewed from the longitudinal direction, The interval between adjacent partition plates in the second structure is 50 mm to 200 mm; The height from the inner surface to the free end of the partition plate in the second structure is 100 mm to 400 mm; The second structure is characterized by reducing noise in the range of 200 Hz to 800 Hz through air column resonance.

[0011] [ 3 ] Another aspect of the in-pipe sound suppression structure according to the present invention is as follows: A pipe-transmitting sound suppression structure comprising a pipe body and three or more partition plates fixed to an inner surface of the pipe body and arranged at intervals along a longitudinal direction of the pipe body, A first structure having a sound absorbing material 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 material and the inner surface; A second structure in which the free end sides of the adjacent partition plates are open; Equipped with The partition plates are disposed so as to intersect with the longitudinal direction, and the partition plates are disposed in an annular shape as viewed from the longitudinal direction, The first structures and the second structures are arranged alternately along the longitudinal direction. Effect of the Invention

[0012] According to the in-pipe sound propagation suppression structure of the present invention, an excellent noise reduction effect can be obtained and costs can be reduced. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram illustrating a pipe propagation sound suppression structure according to an embodiment of the present invention. FIG. [Diagram 2] FIG. 2 is a diagram for explaining the arrangement of a first structure and a second structure in test specimens of an example and a comparative example. [Diagram 3] FIG. 2 is a diagram for explaining the arrangement of a first structure and a second structure in test specimens of an example and a comparative example. [Figure 4] FIG. 2 is a vertical cross-sectional view illustrating the arrangement of a sound source, measurement points, and a test specimen. [Diagram 5] 3 is a graph showing the noise reduction effects of Example 1 and Comparative Examples 1 and 2. [Figure 6] 4 is a graph showing the noise reduction effects of Example 2 and Comparative Examples 1 and 2. [Figure 7] 4 is a graph showing the noise reduction effects of Example 3 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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 contents of the present invention described in the claims. In addition, not all of the configurations described below are necessarily essential components of the present invention.

[0015] The pipe propagation sound suppression structure 2 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic diagram for explaining the pipe propagation sound suppression structure 2 according to this embodiment, in which (a) is an AA cross-sectional view of the pipe propagation sound suppression structure 2 in (b), and (b) is a BB cross-sectional view of the pipe propagation sound suppression structure 2 in (a). In Fig. 2 (a), a part of the partition plate 300 and the sound absorbing material 400 that do not appear on the end surface are shown by dashed lines in order to clearly show the cross-sectional shape.

[0016] As shown in Fig. 1, the in-pipe sound propagation suppression structure 2 includes a pipe body 20 and three or more partition plates 300 fixed to the inner surface 22 of the pipe body 20 and arranged at intervals along the longitudinal direction D of the pipe body 20. The number of partition plates 300 in the pipe body 20 can be increased or decreased depending on the length of the pipe body 20 and the required suppression effect of the propagated sound, and Fig. 1 illustrates an example in which five partition plates are used.

[0017] The tube 20 extends in a longitudinal direction D from a first opening 24 to a second opening 26 that open at both ends of the tube 20. The longitudinal direction D is the longitudinal direction of the range of the tube 20 in which the partition plate 300 is arranged, even when the tube 20 is bent. The longitudinal direction D is also the direction of sound propagation in that range, and is the direction along the axial direction of the tube 20 (X direction).

[0018] The pipe body 20 is, for example, a duct provided in a building. The pipe body 20 has an inner surface 22 that is rectangular when viewed from the front, but is not limited thereto and may be, for example, a polygon other than a rectangle, a circle, a semicircle, or the like. 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 zinc-plated iron plate, a galvalume steel plate (registered trademark), or a stainless steel plate, or a synthetic resin, such as rigid polyvinyl chloride.

[0019] The pipe 20 has the same pipe diameter in the longitudinal direction D, but is divided into a plurality of different pipe diameters. 2, the area between the first opening 24 and the partition plate 300 at the left end of the drawing may have a first pipe diameter that is substantially the same as the first opening 24, the area where the multiple partition plates 300 are located may have a second pipe diameter that is larger than the first pipe diameter, and the area between the partition plate 300 at the right end of the drawing and the second opening 26 may have the first pipe diameter.

[0020] The partition plate 300 is disposed so as to protrude from the inner surface 22 toward the center of the tube body 20. Therefore, a noise reduction effect is obtained on each surface of the inner surface 22 of the tube body 20. The partition plate 300 is disposed so as to intersect (orthogonal in this example) with the longitudinal direction D, and the partition plate 300 is disposed in a ring shape as viewed from the longitudinal direction D. That is, the partition plate 300 is provided in a ring shape by continuing along the inner surfaces 22 of the top surface, bottom surface, and both sides as viewed from the front, and is a single plate-like body having an opening in the center as shown in (b) of FIG. 1. The ring shape is not limited to the shape of the opening and the outer shape, but includes a shape that continues around the central opening as viewed from the longitudinal direction D as shown in (b) of FIG. 1, and includes, for example, a ring shape in which the opening and the outer shape of the partition plate 300 are both ring-shaped so as to form the sides of a rectangle as in this embodiment, and also includes a ring shape in which the opening and the outer shape are both circular. The partition plate 300 is preferably fixed to the entire circumference of the inner surface 22 as shown in Fig. 1, but is not limited thereto and may be fixed to only a portion of the inner surface 22, for example, to both opposing side surfaces. The partition plate 300 may be a single plate body with an opening provided in the center as shown in Fig. 1, or a single plate body formed by joining multiple plates together, or a single plate body formed by arranging multiple plates side by side.

[0021] The partition plate 300 is, for example, a plate-like body extending in the YZ direction and erected in the vertical direction with respect to the inner surface 22. The partition plates 300 are arranged on the inner surface 22 at intervals along the propagation direction of the propagating sound (the longitudinal direction D of the tube body 20). The interval between adjacent partition plates 300 can be set according to the diameter of the tube body 20 and the desired propagation sound suppression effect, and is, for example, 50 mm to 200 mm. The partition plate 300 has a fixed end 320 at the lower end fixed on the inner surface 22. The partition plate 300 has a free end 340 on the opposite side to the fixed end 320. The free end 340 is a portion that forms the edge of an opening (see FIG. 1(a)) in the center of the partition plate 300. The opening of the partition plate 300 is preferably provided in the center of the partition plate 300 because a noise reduction effect due to air column resonance can be obtained in the distance from the free end 340 to the inner surface 22, but the center of the partition plate 300 and the center of the opening do not have to coincide. The shape of the opening of the partition plate 300 is preferably similar to that of the inner surface 22 as shown in Fig. 1(b), and is not limited to a quadrangle, and may be, for example, a circle or a polygon to match the shape of the inner surface 22.

[0022] The height of the partition plate 300 is the height from the inner surface 22 to the free end 340, and can be set according to the diameter of the tube body 20 and the desired effect of suppressing transmitted sound, and is, for example, 100 mm to 400 mm. The material of the partition plate 300 can be any material generally used as a sound insulating material, such as metal, glass, resin, or wood.

[0023] Three or more partition plates 300 are arranged on the inner surface 22. The number of partition plates 300 can be set according to the required effect of suppressing transmitted sound. The partition plates 300 and the inner surface 22 can be joined by an appropriate joining method according to the materials of both plates. For example, if both plates are metal, welding, bolt joining, etc. can be used, and if both plates are synthetic resin, adhesion, welding, etc. can be used. Since a noise reduction effect due to air column resonance can be obtained between adjacent partition plates 300, it is preferable to have a large number of partition plates 300. The noise reduction effect due to air column resonance of partition plates 300 having a predetermined height and interval can be obtained mainly between 200 Hz and 800 Hz.

[0024] The in-pipe sound propagation suppression structure 2 includes a first structure 11 and a second structure 12. The in-pipe sound propagation suppression structure 2 preferably includes a plurality of first structures 11 and a plurality of second structures 12. The first structures 11 and the second structures 12 are configured using the above-mentioned partition plate 300.

[0025] The first structure 11 has a sound-absorbing material 400 extending from a free end 340 of one adjacent partition plate 300 to a free end 340 of the other adjacent partition plate 300, and an air layer 50 provided between the sound-absorbing material 400 and the inner surface 22. The sound-absorbing material 400 has a length equal to the interval between the adjacent partition plates 300.

[0026] The sound-absorbing material 400 is provided at the free end 340 of the partition plate 300, and the first structure 11 has a structure in which the space between adjacent partition plates 300 is covered with the sound-absorbing material 400. Therefore, as shown in FIG. 1(b), the sound-absorbing material 400 is provided in an annular shape along the opening formed by the free end 340 of the partition plate 300, and an air layer 50 is formed in an annular shape along the outer periphery of the sound-absorbing material 400. The sound-absorbing material 400 is installed flush with the free end 340, but may protrude slightly from the free end 340. The sound-absorbing material 400 is arranged at a predetermined interval from the inner surface 22.

[0027] The sound absorbing material 400 may be made of glass wool, rock wool, a porous material, or the like. The porous material may be, for example, activated carbon. The sound absorbing material 400 is preferably made of glass wool in view of its price and ease of handling.

[0028] The method of attaching sound-absorbing material 400 to free end 340 can be determined according to the materials of both, but because glass wool, rock wool, etc. are flexible and difficult to fix, it is preferable to provide a member for attaching sound-absorbing material 400 to partition plate 300 in advance. Maintenance will be required to check the attachment state of sound-absorbing material 400 or to replace it, and the presence of second structure 12 within the pipe makes it possible to utilize the space during maintenance.

[0029] The air space 50 is formed between adjacent partition plates 300, between the sound-absorbing material 400 and the inner surface 22. The first structure 11 has an excellent noise reduction effect mainly for frequencies of 800 Hz or more by providing the air space 50 covered with the sound-absorbing material 400.

[0030] The second structure 12 is open on the free end 340 side of the adjacent partition plate 300. The second structure 12 has a noise reduction effect due to air column resonance of the partition plate 300 having a predetermined height and interval, mainly between 200 Hz and 800 Hz. Moreover, since the second structure 12 does not have the sound absorbing material 400, it is superior to the first structure 11 in terms of noise reduction effect due to air column resonance at 200 Hz to 800 Hz. According to the in-pipe sound propagation suppression structure 2, a superior noise reduction effect can be obtained by providing the second structure 12 compared to a structure having only the first structure 11. Furthermore, according to the in-pipe sound propagation suppression structure 2, since the second structure 12 does not have the sound absorbing material 400, it is possible to reduce costs compared to a structure having only the first structure 11, and the effort of installing the sound absorbing material 400 can also be reduced. Furthermore, it is also possible to use the second structure 12 as a space for performing maintenance on the first structure 11.

[0031] The first structures 11 and the second structures 12 are preferably arranged alternately along the longitudinal direction D. Arranging the first structures 11 and the second structures 12 alternately provides a better effect of reducing air column resonance noise at 200 Hz to 400 Hz than providing the second structures 12 continuously. In addition, the noise reduction effect in a specific frequency band changes by changing the number of first structures 11 and the number of second structures 12 installed, or the number of first structures 11 arranged consecutively and the number of second structures 12 arranged consecutively, and so on, so the number and arrangement of the first structures 11 and the second structures 12 may be adjusted in accordance with the frequency characteristics of the noise source.

[0032] The pipe propagation sound suppression structure 2 can be used in, for example, tunnels, offices, hospitals, schools, factories, and the like. EXAMPLES

[0033] [Test specimen] The test specimens 2a to 2f will be described with reference to Figs. 2, 3 and 4. Fig. 2 shows the test specimens 2a to 2f of the embodiment and Fig. 2 is a diagram for explaining the arrangement of the first structure 11 and the second structure 12 in the test bodies 2a to 2c of the comparative example, Fig. 3 is a diagram for explaining the arrangement of the first structure 11 and the second structure 12 in the test bodies 2d and 2e of the embodiment and the comparative example, and Fig. 3 is a vertical cross-sectional view for explaining the arrangement of the speaker 6, the measurement point 7, and the test body 2f. Each of Figs. 2(a) to (c) and Fig. 3(d) and (e) shows a vertical cross-sectional view of each test body 2a to 2e on the left side and a front view of each test body 2a to 2e on the right side. The broken lines indicate the sound-absorbing material 400.

[0034] FIG. 2(a) shows a test specimen 2a of Comparative Example 1. The test specimen 2a was a cylinder made of a polyvinyl chloride pipe body 20b having a height of 750 mm and ten partition plates 300, and polyvinyl chloride pipe bodies 20a and 20c having a square first opening 24 and a second opening 26 having a height of 350 mm joined to both ends of the pipe body 20b. Both ends of the pipe body 20b were provided with a partition plate 300 having a square opening of 350 mm in height at the center, and the opening of the partition plate 300 was connected to the opening of the pipe body 20a and 20c. The test specimen 2a had a structure in which ten partition plates 300 having a thickness of 5 mm were arranged at intervals of 50 mm from a position 250 mm to a position 750 mm from the first opening 24, and sound-absorbing materials 400 having a length of 50 mm were fixed between adjacent partition plates 300, and nine first structures 11 were arranged along the longitudinal direction D. The height of the partition plate 300 from the inner surface 22 (the distance from the fixed end 320 to the free end 340) was 200 mm, and the square opening formed by the free end 340 was 350 mm wide. The sound-absorbing material 400 had a length of 50 mm along the longitudinal direction D, a thickness of 50 mm, and a length of 350 mm along the free end 340, and was made of glass wool (32 kg / m3). The air layer 50 had a height of 150 mm from the inner surface 22.

[0035] 2(b) shows the specimen 2b of Example 1. The specimen 2b had four second structures 12 lined up along the longitudinal direction D from the first opening 24 side, followed by five first structures 11 lined up. The shapes and materials of the partition plate 300 and the sound-absorbing material 400 were the same as those of the specimen 2a of Comparative Example 1.

[0036] 2(c) shows specimen 2c of Example 2. Specimen 2c had two second structures 12 lined up along the longitudinal direction D from the first opening 24 side, followed by seven first structures 11 lined up. The shapes and materials of the partition plate 300 and the sound-absorbing material 400 were the same as those of specimen 2a of Comparative Example 1.

[0037] 3(d) shows specimen 2d of Example 3. Specimen 2d had a structure in which first structures 11 and second structures 12 were alternately arranged from the first opening 24 side along the longitudinal direction D. The shapes and materials of the partition plate 300 and the sound-absorbing material 400 were the same as those of specimen 2a of Comparative Example 1.

[0038] 3(e) is the specimen 2e of Comparative Example 2. The specimen 2e had nine second structures 12 arranged along the longitudinal direction D from the first opening 24 side, and had a structure without a sound absorbing material. The shape and material of the partition plate 300 were the same as those of the specimen 2a of Comparative Example 1.

[0039] 4 was a rectangular tubular body 20 made of polyvinyl chloride having a square opening of height 350 mm and no partition plate 300 or sound-absorbing material 400 on its inner surface 22. The test body 2f was a test body that served as a standard for comparison when measuring the sound pressure levels of the test bodies 2a to 2e.

[0040] [Sound pressure level measurement] The test specimens 2a to 2f were placed in the apparatus shown in Fig. 4 with the first opening 24 facing downwards, as with the test specimen 2f, and the sound pressure level (dB) of each was measured. Fig. 4 is a vertical cross-sectional view explaining the arrangement of the speaker 6, which is the sound source, and the measurement point 7. In Fig. 4, the test specimen 2f is placed at the center on a plywood board 4 with an opening, and the speaker 6 is placed so as to cover the opening of the plywood board 4. A buffer material 5 is provided between the plywood board 4 and the speaker 6. The speaker 6 was manufactured by WASEDA EEW- A 3232 flat speaker (300 x 300 mm) was used. Pink noise was used as the test sound, and the input voltage was constant regardless of the measurement conditions. The test specimen 2f was placed with the first opening 24 on the plywood board 4 so that the sound propagation direction passed along the central axis of the test specimen 2f. The distance between the center of the second opening 26 and the measurement point 7 was 500 mm. The device in Figure 4 was placed in an anechoic chamber.

[0041] First, the test specimen 2f was placed in the device, and a reference sound pressure level was measured at the measurement point 7 while emitting a test sound from the speaker 6. Next, the test specimen 2f was replaced with the test specimens 2a to 2e shown in Figs. 2 and 3, and the sound pressure levels of each were similarly measured and compared with the sound pressure level of the test specimen 2f.

[0042] Figures 5 to 7 show the noise reduction effect (dB) of test specimens 2a to 2e relative to test specimen 2f at 100 Hz to 1.25 kHz. In Figures 5 to 7, the horizontal axis is frequency (Hz), and the vertical axis is noise reduction effect (dB) indicating the amount of reduction in sound pressure level of test specimens 2a to 2e relative to the sound pressure level of test specimen 2f.

[0043] As shown in Figure 5, specimen 2b (▲) of Example 1 had a greater noise reduction effect at all frequencies than specimen 2e (×) of Comparative Example 2, and had a greater noise reduction effect at 250 Hz to 400 Hz than specimen 2a (●) of Comparative Example 1.

[0044] As shown in Figure 6, specimen 2c (■) of Example 2 had a greater noise reduction effect at all frequencies than specimen 2e (×) of Comparison Example 2, a greater noise reduction effect at 250 Hz to 400 Hz than specimen 2a (●) of Comparison Example 1, and had equivalent noise reduction effects at 100 Hz to 200 Hz and 500 Hz to 1.25 kHz.

[0045] As shown in Figure 7, specimen 2d of Example 3 (◯) had a greater noise reduction effect at all frequencies than specimen 2e of Comparison Example 2 (×), and had a greater noise reduction effect at 200 Hz to 315 Hz than specimen 2a of Comparison Example 1 (●).

[0046] 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 those described in the embodiments (for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effect). 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 achieve the same effects as the configurations described in the embodiments, or configurations that can achieve the same purpose. The present invention also includes configurations in which publicly known technology is added to the configurations described in the embodiments. [Explanation of symbols]

[0047] Reference Signs: 2... Structure for suppressing sound propagation within a pipe, 2a to 2f... Test specimen, 4... Plywood, 5... Cushioning material, 6... Speaker, 7... Measurement point, 11... First structure, 12... Second structure, 20, 20a, 20b, 20c... Pipe body, 22... Inner surface, 24... First opening, 26... Second opening, 50... Air layer, 300... Partition plate, 320... Fixed end, 340... Free end, 400... Sound absorbing material, D... Longitudinal direction

Claims

1. A pipe-transmitting sound suppression structure comprising a pipe body and three or more partition plates fixed to an inner surface of the pipe body and arranged at intervals along a longitudinal direction of the pipe body, A first structure including a sound absorbing material 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 material and the inner surface; A second structure in which the free end sides of the adjacent partition plates are open; Equipped with The partition plates are disposed so as to intersect with the longitudinal direction, and the partition plates are disposed in an annular shape as viewed from the longitudinal direction, A structure for suppressing sound propagation within a pipe, characterized in that it is possible to reduce noise in a specific frequency band in accordance with the frequency characteristics of a noise source by changing one or more of the number of the first structures, the number of the second structures, the number of the first structures arranged in succession, and the number of the second structures arranged in succession.

2. A pipe-transmitting sound suppression structure comprising a pipe body and three or more partition plates fixed to an inner surface of the pipe body and arranged at intervals along a longitudinal direction of the pipe body, A first structure including a sound absorbing material 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 material and the inner surface; A second structure in which the free end sides of the adjacent partition plates are open; Equipped with The partition plates are disposed so as to intersect with the longitudinal direction, and the partition plates are disposed in an annular shape as viewed from the longitudinal direction, The interval between adjacent partition plates in the second structure is 50 mm to 200 mm, The height from the inner surface to the free end of the partition plate in the second structure is 100 mm to 400 mm, An in-pipe sound propagation suppression structure, characterized in that the second structure reduces noise between 200 Hz and 800 Hz by air column resonance.

3. A pipe-introducing sound suppression structure comprising a pipe body and three or more partition plates fixed to the inner surface of the pipe body and arranged at intervals along the longitudinal direction of the pipe body, A first structure including a sound absorbing material 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 material and the inner surface; A second structure in which the free end sides of the adjacent partition plates are open; Equipped with The partition plates are disposed so as to intersect with the longitudinal direction, and the partition plates are disposed in an annular shape as viewed from the longitudinal direction, A structure for suppressing sound propagation within a pipe, characterized in that the first structure and the second structure are arranged alternately along the longitudinal direction.

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