WO2024090085A1 - 消音構造体 - Google Patents

消音構造体 Download PDF

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Publication number
WO2024090085A1
WO2024090085A1 PCT/JP2023/034419 JP2023034419W WO2024090085A1 WO 2024090085 A1 WO2024090085 A1 WO 2024090085A1 JP 2023034419 W JP2023034419 W JP 2023034419W WO 2024090085 A1 WO2024090085 A1 WO 2024090085A1
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WIPO (PCT)
Prior art keywords
sound
flow path
absorbing material
path
main flow
Prior art date
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Ceased
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PCT/JP2023/034419
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English (en)
French (fr)
Japanese (ja)
Inventor
真也 白田
昇吾 山添
美博 菅原
雄一郎 板井
俊 石毛
知宏 ▲高▼橋
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Fujifilm Corp
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Fujifilm Corp
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Publication date
Application filed by Fujifilm Corp filed Critical Fujifilm Corp
Priority to CN202380074832.5A priority Critical patent/CN120092283A/zh
Priority to EP23882297.7A priority patent/EP4610975A4/en
Priority to JP2024552887A priority patent/JPWO2024090085A1/ja
Publication of WO2024090085A1 publication Critical patent/WO2024090085A1/ja
Priority to US19/092,029 priority patent/US20250225967A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/161—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general in systems with fluid flow
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/162—Selection of materials
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound

Definitions

  • the present invention relates to a sound-absorbing structure.
  • Patent Document 1 describes an interference type silencer in which a portion of the exhaust duct of an automobile engine or the like is provided with multiple exhaust gas branch passages with different flow path lengths, and these exhaust gas passages are merged into the exhaust duct.
  • Silencers that use interference require a length difference of ⁇ /2, which limits how small they can be made.
  • the objective of the present invention is to solve the problems of the above-mentioned conventional technology and to provide a noise reduction structure that uses interference and can be made compact while maintaining its noise reduction performance.
  • the present invention has the following configuration.
  • a main flow path connected to an inlet and an outlet;
  • At least a sound absorbing material is disposed at a connecting position between the main flow path and the sub flow path,
  • the secondary flow path is not directly connected to the inlet and outlet, a path length when passing through the sub-path from the inlet to the outlet is equal to or longer than a path length when passing through only the main path from the inlet to the outlet;
  • This sound-absorbing structure silences sounds of a frequency to be silenced by causing interference between the sound that passes through a path that passes only the main flow path and the sound that passes through a path that passes through the secondary flow path, the phase difference being greater than 90 degrees and smaller than 270 degrees.
  • [2] The sound-absorbing structure according to [1], wherein the total thickness of the sound-absorbing material in the path direction passing through the sub-flow path is 10 mm or more.
  • [3] The sound deadening structure according to [1] or [2], wherein the main flow path and the sub flow path are separated by a non-air-permeable wall member except for the connection position.
  • [4] The sound-absorbing structure according to any one of [1] to [3], wherein the sound-absorbing material has a viscous characteristic length of 300 ⁇ m or less.
  • [5] The sound-absorbing structure according to any one of [1] to [4], wherein the tortuosity of the sound-absorbing material is 1.1 or more.
  • a fan is connected to the inlet, and the main flow path acts as a ventilation path;
  • the sound deadening structure according to any one of [1] to [8], wherein the sound to be silenced is fan sound.
  • the present invention provides a noise reduction structure that uses interference and can be made compact while still maintaining noise reduction performance.
  • FIG. 1 is a cross-sectional view conceptually showing an example of a sound deadening structure of the present invention.
  • 2 is a cross-sectional view taken along line AA in FIG. 1.
  • 2 is a cross-sectional view taken along line BB in FIG. 1.
  • FIG. 2 is a diagram showing the phase of sound passing through a sound-absorbing structure.
  • FIG. 2 is a cross-sectional view conceptually showing another example of the sound deadening structure of the present invention.
  • 1 is a graph showing the relationship between frequency and transmission loss.
  • 1 is a graph showing the relationship between frequency and transmission loss.
  • FIG. 2 is a diagram showing the phase of sound passing through a sound-absorbing structure.
  • 1 is a graph showing the relationship between frequency and transmission loss.
  • FIG. 2 is a cross-sectional view of a sound deadening structure for explaining the configuration of an embodiment.
  • 1 is a graph showing the relationship between frequency and transmission loss.
  • 1 is a graph showing the relationship between the thickness of a sound-absorbing material and a peak frequency.
  • 1 is a graph showing the relationship between tortuosity and peak muffling frequency.
  • 1 is a graph showing the relationship between the viscous characteristic length and the tortuosity and the speed of sound.
  • 1 is a graph showing the relationship between the viscous characteristic length and the tortuosity and the speed of sound.
  • FIG. 1 is a graph showing the relationship between the viscous characteristic length and the tortuosity and the speed of sound.
  • FIG. 2 is a cross-sectional view conceptually showing another example of the sound deadening structure of the present invention.
  • FIG. 2 is a diagram showing the phase of sound passing through a sound-absorbing structure.
  • a numerical range expressed using “to” means a range that includes the numerical values before and after "to” as the lower and upper limits.
  • “orthogonal”, “vertical”, and “parallel” include the range of error permitted in the technical field to which the present invention pertains.
  • orthogonal means that the error is within a range of less than ⁇ 10° from the strict orthogonal, vertical, or parallel, and the error from the strict orthogonal, vertical, or parallel is preferably 5° or less, and more preferably 3° or less.
  • terms such as “same” are intended to include a margin of error generally accepted in the technical field.
  • the sound deadening structure of the present invention is A main flow path connected to the inlet and the outlet; A secondary flow path that branches off from the main flow path and returns to the main flow path; At least a sound absorbing material is disposed at a connecting position between the main flow path and the sub flow path, The secondary flow path is not directly connected to the inlet and outlet, a path length when passing only through the main flow path from the inlet to the outlet is equal to or less than a path length when passing through the sub-flow path from the inlet to the outlet,
  • This is a sound-absorbing structure in which the phase difference between the sound that passes through a path that passes only the main flow path and the sound that passes through a path that passes through the secondary flow path is greater than 90 degrees and less than 270 degrees, causing interference and silencing the sound, for the sound of the frequency to be silenced.
  • Fig. 1 is a schematic cross-sectional view showing an example of an embodiment of the sound deadening structure of the present invention
  • Fig. 2 is a cross-sectional view taken along line AA in Fig. 1
  • Fig. 3 is a cross-sectional view taken along line BB in Fig. 1.
  • the sound deadening structure 10 shown in FIG. 1 has an air duct that constitutes a main flow path 12, an air duct that constitutes a secondary flow path 14 that branches off from and merges with the main flow path 12, and a sound absorbing material 16.
  • the main flow path 12 is a flow path that is connected to the inlet 12a and the outlet 12b.
  • the main flow path 12 is a linear flow path from the inlet 12a to the outlet 12b.
  • the shape and size of the cross section of the main flow path 12 perpendicular to the flow path direction are constant from the inlet 12a to the outlet 12b.
  • the cross-sectional shape of the main flow path is approximately rectangular.
  • the main flow path 12 has a connection position 13a on the lower surface at the inlet 12a side that connects to the secondary flow path 14, and a connection position 13b on the outlet 12b side that connects to the secondary flow path 14.
  • the sub-channel 14 is a channel that branches off from the main channel 12 at the connection position 13a and returns to the main channel 12 at the connection position 13b. That is, the connection position 13a is a branching portion, and the connection position 13b is a junction portion. In the example shown in Figs.
  • the sub-channel 14 has a first portion that extends from the connection position 13a in a direction that is substantially perpendicular to the flow direction of the main channel 12, toward the bottom in the illustrated example, a second portion that extends from the end of the first portion opposite the connection position 13a, the bottom end in the illustrated example, substantially parallel to the flow direction of the main channel 12, in the left-right direction in the illustrated example, toward the outlet 12b side, and a third portion that extends from the end of the second portion opposite the first portion, the right end in the illustrated example, in a direction that is substantially perpendicular to the flow direction of the main channel 12, toward the top in the illustrated example, to the connection position 13b.
  • the shape and size of the cross section perpendicular to the flow direction of the secondary flow path 14 are constant from connection position 13a to connection position 13b.
  • the flow direction of the secondary flow path 14 at the first portion is the up-down direction in the figure
  • the flow direction at the second portion is the left-right direction in the figure
  • the flow direction at the third portion is the up-down direction in the figure.
  • the cross-sectional shape of the secondary flow path is approximately rectangular.
  • the sub-channel 14 is only connected to the main channel 12 at connection positions 13a and 13b, and is not directly connected to the inlet 12a and outlet 12b.
  • the main channel 12 and the sub-channel 14 are separated by a non-breathable wall member 15 except at connection positions 13a and 13b.
  • the path length (path length Rs) when passing through the sub-channel 14 is equal to or greater than the path length Rm when passing only through the main channel 12.
  • the path length Rm when passing only through the main channel 12 is the length along the flow direction of the main channel 12 from the inlet 12a to the outlet 12b.
  • the path length Rs when passing through the sub-channel 14 is the sum of the length along the flow direction of the main channel 12 from the inlet 12a to the connection position 13a, the length along the flow direction of the sub-channel 14 from the connection position 13a to the connection position 13b, and the length along the flow direction of the main channel 12 from the connection position 13b to the outlet 12b.
  • the sound absorbing material 16 is placed at least at the connection positions 13a and 13b between the main flow path 12 and the secondary flow path 14. In the illustrated example, it is placed at the first and second parts of the secondary flow path 14, respectively.
  • the shape and size of the sound absorbing material 16 in cross sections perpendicular to the flow path direction of the first and second parts are approximately the same as the cross-sectional shape and size of the secondary flow path 14, and it fills a part of the secondary flow path 14.
  • the sound absorbing material 16 is not disposed within the main flow path 12, but is disposed flush with the wall member in which the connection positions 13a and 13b are formed (the lower wall member in FIG. 1).
  • the sound absorbing material 16 is passed through by the sound absorbing structure 10 when the sound passes through the secondary flow path 14, delaying the phase of the sound passing through the secondary flow path 14.
  • the sound absorbing material 16 has a complex internal structure, and therefore has the effect of slowing down the speed of sound passing through the sound absorbing material 16. Therefore, the phase delay is greater when the sound passes through the sound absorbing material 16 than when the sound propagates through the same length of air.
  • the sound absorbing structure 10 uses the effect of the sound absorbing material 16 to create interference and mute the sound of the frequency to be mute, by making the phase difference between the sound passing through the path that passes only through the main flow path 12 and the sound passing through the path that passes through the secondary flow path 14 greater than 90 degrees and less than 270 degrees.
  • the sound deadening structure of the present invention has a sound absorbing material 16 arranged at the connection position between the main flow path 12 and the secondary flow path 14, so that when sound passes through the path that passes through the secondary flow path 14, it passes through the sound absorbing material 16, and the phase of the sound passing through the path that passes through the secondary flow path 14 can be delayed.
  • the phase difference between the sound passing through only the main flow path 12 and the sound passing through the secondary flow path 14 can be made greater than 90 degrees and smaller than 270 degrees, and the sound can be silenced by interference. Therefore, the sound deadening structure can be made smaller in size.
  • the sound absorbing material 16 is lightweight, the weight of the entire sound deadening structure can be reduced.
  • Figure 4 shows the sound pressure distribution in the sound deadening structure obtained by simulation in Example 1 described later. As shown in Figure 4, the sound pressure phases of the sound passing only through the main flow path 12 and the sound passing through the secondary flow path 14 are almost opposite at the joining point, connection position 13b. Therefore, interference occurs in the flow paths after connection position 13b, canceling each other out and causing the sound to be deadened.
  • the phase difference between the sound passing only through the main flow path 12 and the sound passing through the sub-flow path 14 for the sound of the frequency to be silenced is preferably 135° to 225°, and more preferably 160° to 200°.
  • the phase difference is defined as "abs( ⁇ ) mod 360" (the remainder when the absolute value of the phase difference between the two paths is divided by 360 degrees), where ⁇ is the phase difference between the main path and the sub-path.
  • the frequency of the sound targeted for muffling is preferably 50 Hz to 4000 Hz, and more preferably 100 Hz to 3000 Hz.
  • the total thickness of the sound-absorbing material 16 in the path direction passing through the secondary flow path is preferably 10 mm or more, more preferably 15 mm or more, and even more preferably 20 mm or more.
  • the total thickness of the sound-absorbing material 16 in the path direction passing through the secondary flow passage is preferably 100 mm or less, more preferably 60 mm or less, and even more preferably 40 mm or less.
  • the total thickness of the sound-absorbing material 16 in the path direction passing through the secondary flow path 14 is the sum of the vertical thickness of the sound-absorbing material 16 arranged in the first portion of the secondary flow path 14 and the vertical thickness of the sound-absorbing material 16 arranged in the second portion.
  • the sound absorbing material 16 is arranged in a part of the secondary flow path 14, but this is not limited thereto, and the sound absorbing material 16 may be arranged over the entire secondary flow path 14. However, if the sound absorbing material 16 is arranged over the entire secondary flow path 14, the sound absorbing effect of the sound absorbing material 16 becomes large, and there is a risk that the sound absorbing effect due to cancellation caused by interference will be reduced. Therefore, it is preferable to arrange the sound absorbing material 16 in a part of the secondary flow path 14.
  • the sound absorbing material 16 is arranged near the connection position 13a (branch) and the connection position 13b (confluence) of the main flow path 12 and the sub-flow path 14, but this is not limited to the above.
  • the sub-flow path 14 may further have a sound absorbing material arranged in a part of the second part of the sub-flow path 14.
  • the sub-flow path 14 may have a sound absorbing material arranged in at least a part of the second part of the sub-flow path 14.
  • the sound absorbing material 16 is arranged near the connection position 13a and the connection position 13b of the main flow path 12 and the sub-flow path 14 so as to prevent wind from flowing into the sub-flow path 14.
  • the sound-absorbing material 16 is arranged flush with the wall member (the lower wall member in Figure 1) in which the connection positions 13a and 13b are formed, near the connection positions 13a and 13b of the secondary flow path 14, respectively. If at least a part of the sound absorbing material 16 is disposed within the main flow path 12, for example, when the sound deadening structure 10 is connected to an air duct and the main flow path 12 is used as an air passage, the sound absorbing material 16 may obstruct the air flow and reduce the amount of air flow.
  • connection positions 13a and 13b of the sub-flow path 14 if the sound absorbing material 16 is disposed at a position other than the connection positions 13a and 13b of the sub-flow path 14, a step is created at the connection positions 13a and 13b, which may disturb the air flowing through the main flow path 12 and cause wind noise. Since the sound-absorbing material 16 almost completely blocks wind and allows sound to pass through, by arranging the sound-absorbing material 16 flush with the wall member in which the connection positions 13a and 13b are formed, it is possible to prevent the ventilation from being obstructed and also to prevent the generation of wind noise.
  • the viscosity characteristic length of the sound-absorbing material 16 is 300 ⁇ m or less, more preferably 1 ⁇ m or more and 100 ⁇ m or less, even more preferably 5 ⁇ m or more and 70 ⁇ m or less, and particularly preferably 10 ⁇ m or more and 50 ⁇ m or less.
  • the tortuosity of the sound absorbing material 16 is preferably 1.1 or more, more preferably 1.2 or more and 5.0 or less, and further preferably 1.5 or more and 4.0 or less.
  • the viscous characteristic length is a quantity related to the effective density of the porous material in the JCA model (Johnson-Champoux-Allard-Lafarge model) or Biot model, and represents the viscous loss (attenuation) caused by the violent movement of air in the narrow voids.
  • Meandering degree is one of the parameters related to the fluid (air) that fills a porous material, and indicates the complexity of the voids inside the porous elastic body, and is defined as the ratio of the speed of sound to the speed of sound in air at the limit of high frequencies. Therefore, ultrasonic waves above the audible range are used to measure the speed of sound passing through the sound-absorbing material, and the ratio to the speed of sound traveling through air is measured. The higher the meandering degree, the more complex the internal structure is, and the greater the effect of slowing down the speed of sound passing through the porous material.
  • the viscosity characteristic length and tortuosity can be measured using a device such as "Torvith” manufactured by Nippon Acoustic Engineering Co., Ltd.
  • the tortuosity is defined as the ratio of the speed of sound to the speed of sound in air at the limit of high frequencies, so it can be obtained by measuring the speed of sound passing through a sound-absorbing material using high-frequency sound (ultrasound) that is above the audible range, and measuring the ratio to the speed of sound traveling through air.
  • the viscosity characteristic length can be measured using two gases with different sound speeds, such as air and argon. Measurements may also be performed using other similar measuring devices, or homemade devices following the definition.
  • microstructure may be modeled using a SEM (scanning electron microscope), 3D-CT (Computed Tomography) scan, laser microscope, etc., and the viscosity characteristic length and tortuosity may be determined according to the definition using fluid calculations.
  • the effective parameters related to absorption in the air part can be expressed as the following formulas (1) and (2). From these two parameters, the velocity inside the sound-absorbing material is ⁇ (K/ ⁇ ).
  • ⁇ tortuosity
  • ⁇ 0 air density
  • ⁇ porosity
  • ⁇ flow resistance
  • i imaginary unit
  • ⁇ angular frequency
  • ⁇ air viscosity
  • ⁇ viscous characteristic length
  • P0 equilibrium pressure
  • ⁇ thermal diffusivity
  • ⁇ ' thermal characteristic length
  • a porous sound absorbing material with a foam structure rather than a woven or nonwoven fabric as the sound absorbing material.
  • nonwoven fabric-based sound absorbing materials have a tortuosity of approximately 1.
  • Porous sound absorbing materials with a foam structure such as urethane foam, can be made to have a tortuosity significantly exceeding 1.
  • by artificially creating a foam structure using a 3D printer or the like it is possible to set the tortuosity and viscosity characteristic length of the porous sound absorbing material to a preferred range.
  • sound-absorbing materials conventionally known sound-absorbing materials can be used as appropriate.
  • various known sound absorbing materials can be used, such as foams, foaming materials (urethane foam (e.g., Calmflex F manufactured by Inoac Corporation, urethane foam manufactured by Hikari Corporation, etc.), soft urethane foam, ceramic particle sintered material, phenol foam, melamine foam, polyamide foam, etc.), nonwoven fabric sound absorbing materials (microfiber nonwoven fabric (e.g., Thinsulate manufactured by 3M, etc.), polyester nonwoven fabric (e.g., White Qon manufactured by Tokyo Soundproofing Co., Ltd., QonPET manufactured by Bridgestone KBG Corporation, Micromat manufactured by Softprene Kogyo Co., Ltd., and these products are also provided in a two-layer structure with a thin surface nonwoven fabric with high density and a back nonwoven fabric with low density), plastic nonwoven fabrics such as acrylic fiber nonwoven fabric, natural fiber nonwoven fabrics such as wool and felt, metal nonwoven fabrics,
  • porous sound absorbing material having a foamed structure As the porous sound absorbing material having a foamed structure, urethane foam such as Calmflex F2, F4, F6, and F9 manufactured by Inoac Corporation and Everlite manufactured by Arkem Corporation can be preferably used.
  • sound-absorbing materials with an artificial, bottom-up foam structure can be created using equipment that can create fine three-dimensional structures, such as 3D printers.
  • the pore size inside the sound-absorbing urethane is about 1 mm, so even a commercially available 3D printer can create it with sufficient resolution. With this method, both the labyrinthness and the viscous characteristic length can be changed as desired.
  • the difference in geometric length between the path length Rm when passing through only the main flow path 12 and the path length Rs when passing through the sub-flow path 14 is not particularly limited as long as Rm ⁇ Rs. However, from the viewpoint of miniaturization while ensuring the phase difference of the sound to be silenced, it is preferable that it is ⁇ /8 or more, and more preferable that it is ⁇ /4 or more.
  • the cross-sectional shapes of the main flow path 12 and the sub-flow path 14 are generally rectangular, but are not limited to this and may be various shapes such as circular or triangular.
  • the cross-sectional shapes of the main flow path 12 and the sub-flow path 14 may be different.
  • the cross-sectional shapes and/or cross-sectional areas of the main flow path 12 and the sub-flow path 14 may not be constant in the flow path direction.
  • the diameter may change in the flow path direction.
  • the secondary flow path 14 is configured to bend at the junction between the first and second portions, and also bend at the junction between the second and third portions, but this is not limited to this.
  • the secondary flow path 14 may have one or more bent portions where the pipeline bends, or may have a curved structure where the pipeline curves.
  • the secondary flow path 14 may also have a structure that has bent portions and a curved structure.
  • the main flow path 12 is a straight pipe, but this is not limited to this.
  • the main flow path 12 may have a bent portion where the pipe is bent and/or a curved structure where the pipe is curved.
  • the main flow path 12 may have a fourth section extending in the left-right direction in the figure (hereinafter referred to as the X direction), a fifth section inclined from one side to the other side (the lower side in FIG. 5) in the Z direction (a direction perpendicular to the X direction, the up-down direction in the figure) as it moves from the fourth section toward the X direction, and a sixth section extending from the fifth section in the X direction.
  • the main flow path 12 of the sound deadening structure 10b shown in FIG. 5 has two bent sections where the pipe is bent, and the positions of the inlet 12a and the outlet 12b in the Z direction are different.
  • the example shown in Figure 5 has a pipe forming the main flow path 12 near the inlet 12a, a pipe forming the main flow path 12 near the outlet 12b, and an expansion section 18 that is expanded beyond the cross-sectional area of these pipes.
  • the pipe on the inlet 12a side is connected to one side in the X direction of the hollow rectangular expansion section 18, and the pipe on the outlet 12b side is connected to the other side.
  • the position where the pipe on the inlet 12a side connects to the expansion section 18 is different from the position where the pipe on the outlet 12b side connects to the expansion section 18.
  • a wall member 15 is disposed within the extension 18 to define the main flow path 12 by connecting the inlet 12a to the outlet 12b.
  • the wall member 15 is formed so that the main flow path 12 is bent at the joint between the inlet 12a side pipe and the extension 18, and inclined from one side in the Z direction to the other side (the lower side in Figure 5) as it moves in the X direction, and extends in the X direction from the position where the main flow path 12 reaches the other side of the extension 18 in the Z direction to join the pipe on the outlet 12b side.
  • the region different from the region that becomes the main flow path 12 becomes the secondary flow path 14.
  • the region above the main flow path 12 is the secondary flow path 14.
  • the wall member 15 has openings that become the connection positions 13a and 13b between the main flow path 12 and the secondary flow path 14.
  • a sound absorbing material 16 is arranged at each of the connection positions 13a and 13b of the secondary flow path 14.
  • the sound deadening structure 10b configured in this way, when sound passes through a path that passes through the secondary flow path 14, it passes through the sound absorbing material 16, and the phase of the sound passing through the path that passes through the secondary flow path 14 can be delayed. Therefore, even if the difference in geometric length between the path length Rm when passing through only the main flow path 12 and the path length Rs when passing through the secondary flow path 14 is less than ⁇ /2 with respect to the wavelength ⁇ of the sound to be silenced, the phase difference between the sound passing through only the main flow path 12 and the sound passing through the secondary flow path 14 can be made greater than 90° and smaller than 270°, and the sound can be silenced by interference. Therefore, the sound deadening structure can be made smaller in size.
  • the thickness of the sound absorbing material 16 is the thickness in a direction perpendicular to the flow path direction of the main flow path 12. That is, in the example shown in Fig. 5, the thickness of the sound absorbing material 16 arranged at the connection position 13a is the thickness in the direction perpendicular to the opening surface at the connection position 13a, and the thickness of the sound absorbing material 16 arranged at the connection position 13b is the thickness in the direction perpendicular to the opening surface at the connection position 13b.
  • a numerical simulation is performed on the sound-absorbing structure to determine the direction of sound propagation at each position, and the direction of sound progression within the sound-absorbing material, and the "thickness of the sound-absorbing material" can be calculated as the sum of these lengths in the direction of propagation.
  • the inside of the expansion section 18 is separated by the wall member 15, so that an area 20 is also formed at the lower left of the main flow path 12.
  • this area 20 and the main flow path 12 are connected by an opening 21 formed in the wall member 15, and a sound-absorbing material 22 is disposed at the position of the opening 21.
  • the configuration has the sound-absorbing material 22 disposed adjacent to the main flow path 12, and has a back space 20 on the side of the sound-absorbing material 22 opposite the main flow path 12.
  • This configuration can prevent sound waves that enter the sound-absorbing material 22 from the main flow path 12 from being reflected and returning to the main flow path 12, so that the sound-absorbing effect of the sound-absorbing material 22 can be increased.
  • the sound-absorbing structure of the present invention has a structure that uses the main flow path 12, the secondary flow path 14, and the sound-absorbing material 16 to create a phase difference between sound that passes only through the main flow path 12 and sound that passes through the secondary flow path 14, thereby silencing the sound through interference, and may also have a structure that exerts a sound-absorbing effect using the normal sound-absorbing material 22.
  • the configuration has one sub-channel 14, but the present invention is not limited to this, and a configuration having two or more sub-channels may be used.
  • a phase difference may be given to the sound passing through the path that passes only through the main path in each of the paths that pass through the sub-channels, and the sound is silenced by interference.
  • the frequencies of the sounds to be silenced may be different for each sub-channel.
  • the frequency to be silenced for the first sub-channel is set to f 1
  • the phase difference between the sound of frequency f 1 passing through the path that passes through the first sub-channel and the sound of frequency f 1 passing through the path that passes only through the main channel is set to be greater than 90° and less than 270°
  • the frequency to be silenced for the second sub-channel is set to f 2
  • the phase difference between the sound of frequency f 2 passing through the path that passes through the second sub-channel and the sound of frequency f 2 passing through the path that passes only through the main channel is set to be greater than 90° and less than 270°, so that the sound of frequency f 1 and the sound of frequency f 2 can be silenced by interference.
  • the geometric path length when passing through the first sub-channel may be made different from the geometric path length when passing through the second sub-channel
  • the parameters (thickness, viscosity characteristic length, tortuosity, etc.) of the sound-absorbing material placed in the first sub-channel may be made different from the parameters (thickness, viscosity characteristic length, tortuosity, etc.) of the sound-absorbing material placed in the second sub-channel, or both may be done.
  • the inlet and outlet of the sound deadening structure of the present invention will be used in connection with other pipelines, it is desirable for the inlet and outlet of the sound deadening structure to have an uneven shape and/or a bellows shape on the outer periphery. This will ensure a tight fit when connected to other pipelines, preventing wind leakage, sound leakage, and sound reflection.
  • the housing that forms the main flow path and the sub-flow path may be constructed, for example, by arranging multiple plate materials in a box shape and joining adjacent plate materials with adhesive, pressure sensitive adhesive, solder, fusion, etc.
  • each piece may be produced by injection molding or a 3D printer, etc., and the pieces may be assembled to form the housing.
  • Materials for forming the housing that constitutes the main flow path and the sub-flow path include metal materials, resin materials, reinforced plastic materials, carbon fiber, etc.
  • Metal materials include, for example, aluminum, titanium, magnesium, tungsten, iron, steel, chromium, chromium molybdenum, nichrome molybdenum, and alloys of these metals.
  • resin materials include acrylic resin (PMMA), polymethyl methacrylate, polycarbonate, polyamide, polyarylate, polyetherimide, polyacetal, polyether ether ketone, polyphenylene sulfide, polysulfone, polyethylene terephthalate, polybutylene terephthalate (PET), polyimide, triacetyl cellulose (TAC), polypropylene (PP), polyethylene (PE), polystyrene (PS), ABS resin (acrylonitrile, butadiene, styrene copolymer synthetic resin), flame-retardant ABS resin, ASA resin (acrylonitrile, styrene, acrylate copolymer synthetic resin), PVC (polyvinyl chloride) resin, and PLA (polylactic acid) resin.
  • reinforced plastic materials include carbon fiber reinforced plastics (CFRP) and glass fiber reinforced plastics (GFRP).
  • the density of the members constituting the sound deadening structure is 0.5 g/cm 3 to 2.5 g/cm 3 .
  • these materials are non-flammable, flame-retardant, and self-extinguishing. It is also desirable that the entire sound-absorbing structure be non-flammable, flame-retardant, and self-extinguishing.
  • the sound-absorbing structure of the present invention can be used as a silencer that is connected to a ventilation passage through which a fluid (gas) flows.
  • the main flow path can be used as the ventilation passage.
  • the sound deadening structure of the present invention may be connected to an air passage through which air generated by a fan flows.
  • a fan may be connected to the inlet of the sound deadening structure.
  • the main flow path acts as an air passage, and the sound generated by the fan is treated as the sound to be silenced, allowing the configuration to silence fan noise.
  • Example 1 Acrylic plates (thickness 3 mm) were processed with a laser cutter, and the processed acrylic plates were combined to form a rectangular parallelepiped cylindrical member with an opening of 20 mm x 20 mm and a length of 100 mm, and a hollow U-shaped member branching off from the cylindrical member and joining together to produce a structure having a main flow path and a sub-flow path as shown in Figure 1.
  • the joints between the acrylic plates were sealed with adhesive and tape.
  • the dimensions of each part were as shown in Figure 12.
  • a sound absorbing material QonPET manufactured by Bridgestone KBG Corporation
  • This sound absorbing material had a thickness of 20 mm, a viscous characteristic length of 100 ⁇ m, and a tortuosity of 1.0.
  • Example 2 A sound-absorbing structure was produced in the same manner as in Example 1, except that Calmflex F6 manufactured by Inoac Corporation was used as the sound-absorbing material. This sound-absorbing material had a thickness of 20 mm, a viscous characteristic length of 100 ⁇ m, and a tortuosity of 1.5.
  • Example 1 A sound-absorbing structure was produced in the same manner as in Example 1, except that no sound-absorbing material was provided.
  • the sound transmission loss of the produced sound deadening structure was measured.
  • the measurement was performed according to the transfer function method (ASTM E2611) using a speaker and four microphone terminals to measure the transmittance and calculate the sound transmission loss.
  • the measurement results of the transmission loss in Example 1 are shown in Fig. 6.
  • the measurement results of the transmission loss in Comparative Example 1 are shown in Fig. 7.
  • the measurement results of the transmission loss in Example 2 are shown in Fig. 9. Moreover, these results are shown together in Fig. 11.
  • the sound-absorbing structures of the examples and comparative examples were modeled and a simulation was performed using the finite element method (COMSOL MultiPhysics ver. 6.0, COMSOL Inc.) to obtain the sound pressure distribution in the sound-absorbing structures.
  • the sound-absorbing material was modeled using the JCA model.
  • the sound pressure distribution at a frequency of 2.27 kHz in Example 1 is shown in Fig. 4.
  • the sound pressure distribution at a frequency of 2.57 kHz in Comparative Example 1 is shown in Fig. 8.
  • the sound pressure distribution at a frequency of 2.03 kHz in Example 2 is shown in Fig. 10.
  • Example 1 high transmission loss appears at 2.27 kHz, which is 300 Hz lower than in Comparative Example 1. From Figure 4, it can be seen that at this frequency of 2.27 kHz, the phase of the sound pressure is inverted at the junction of the main flow path and the sub-flow path, causing cancellation.
  • Example 2 a high transmission loss appears at 2.03 kHz, which is 540 Hz lower than in Comparative Example 1. From Figure 10, it can be seen that at this frequency of 2.03 kHz, the phase of the sound pressure is inverted at the junction of the main flow path and the sub-flow path, causing cancellation.
  • Example 3 A sound-absorbing structure was produced in the same manner as in Example 1, except that the thickness of the sound-absorbing material was changed.
  • the total thickness of the sound-absorbing material was 5 mm (2.5 mm on one side), 10 mm (5 mm on one side), 15 mm (7.5 mm on one side), 20 mm (10 mm on one side), 25 mm (12.5 mm on one side), and 30 mm (15 mm on one side).
  • Example 4 A simulation was performed using the finite element method (COMSOL) in the same manner as in Example 1, except that the viscous characteristic length of the sound-absorbing material was changed to 25 ⁇ m, 50 ⁇ m, and 100 ⁇ m, and the tortuosity was changed to 1, 1.5, and 2.
  • the finite element method (COMSOL) in the same manner as in Example 1, except that the viscous characteristic length of the sound-absorbing material was changed to 25 ⁇ m, 50 ⁇ m, and 100 ⁇ m, and the tortuosity was changed to 1, 1.5, and 2.
  • the sound-absorbing material was modeled using the above-mentioned formulas (1) and (2).
  • the flow resistance was set to 10,000 Rayls, the porosity to 0.90, and the thermal viscous length, which is common for sound-absorbing materials, was set to 2 x viscous characteristic length.
  • the ratio of the sound speed in the sound-absorbing material to the sound speed in air was calculated by changing the tortuosity and viscous characteristic length.
  • Figure 16 shows the results when the sound frequency is 2000 Hz.
  • Figure 17 shows the results when the sound frequency is 1000 Hz.
  • Figure 18 shows the results when the sound frequency is 10,000 Hz. According to A-weighting, 2000 Hz is the frequency band with the highest audibility.
  • a low characteristic viscosity length contributes most to the sound speed ratio, and when the characteristic viscosity length is large, the tortuosity also has a strong influence. Furthermore, when the viscosity characteristic length is 300 ⁇ m or less, the sound speed ratio is less than 0.9 even if the tortuosity is 1.0. When the viscosity characteristic length is less than 100 ⁇ m, not only is the sound speed ratio less than 0.8 at a frequency of 2000 Hz, but it is also less than 0.9 at a frequency of 10000 Hz on the high frequency side.
  • the viscosity characteristic length is 70 ⁇ m or less, the sound speed ratio is less than 0.7, and when the viscosity characteristic length is 50 ⁇ m or less, the sound speed ratio is less than 0.6. In this way, even if the tortuosity is 1.0, the sound speed can be slowed down by reducing the viscosity characteristic length. Therefore, it is understood that the viscosity characteristic length is preferably 300 ⁇ m or less, more preferably 100 ⁇ m or less, further preferably 70 ⁇ m or less, and particularly preferably 50 ⁇ m or less.
  • the tortuosity can be increased, the speed of sound can be slowed even with a large viscosity characteristic length.
  • the tortuosity is 1.1 or more, the sound speed ratio can be sufficiently reduced to 0.9 or less even with a large viscosity characteristic length (up to 1000 ⁇ m), which is effective in creating a phase difference between the main flow path and the sub-flow path.
  • Example 5 A sound deadening structure made of ABS resin as shown in Fig. 19 was produced by injection molding.
  • the thickness of the ABS resin outer wall was set to 3 mm, and a wall member was formed inside the sound deadening structure to separate the main flow path 12 and the sub-flow path 14 (black thick line in Fig. 19).
  • the flow paths on the inlet 12a side and outlet 12b side were square and had a width of 28 mm, and the main flow path 12 and the sub-flow path 14 were fluidically separated using the wall member and sound absorbing material 16 (Calmflex F2 manufactured by Inoac).
  • the flow path width was gradually increased near the connection between the wall member and the sound absorbing material 16, and the wind speed near the sound absorbing material 16 was suppressed, making the structure less likely to generate wind noise.
  • FIG. 20 A simulation was performed using COMSOL in the same manner as above for the sound deadening structure shown in Fig. 19 to calculate the sound pressure distribution inside the sound deadening structure at 2500 Hz.
  • the results are shown in Fig. 20. From Fig. 20, it can be seen that the phase of the sound pressure is inverted at the connection position 13b (junction) of the main flow path 12 and the sub-flow path 14, and the sound is muted due to interference. Also, from Fig. 20, it was possible to clearly simulate how the angle of the sound wavefront (determined by the white part with zero sound pressure) changes and the phase is delayed at the sound-absorbing material 16 at the connection position 13a (branch). The above results clearly show the effectiveness of the present invention.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Chemical & Material Sciences (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Fluid Mechanics (AREA)
  • Exhaust Silencers (AREA)
  • Pipe Accessories (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
PCT/JP2023/034419 2022-10-28 2023-09-22 消音構造体 Ceased WO2024090085A1 (ja)

Priority Applications (4)

Application Number Priority Date Filing Date Title
CN202380074832.5A CN120092283A (zh) 2022-10-28 2023-09-22 消音结构体
EP23882297.7A EP4610975A4 (en) 2022-10-28 2023-09-22 SOUND ATTENUATION STRUCTURE
JP2024552887A JPWO2024090085A1 (https=) 2022-10-28 2023-09-22
US19/092,029 US20250225967A1 (en) 2022-10-28 2025-03-27 Silencing structure

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JP2022-173563 2022-10-28
JP2022173563 2022-10-28

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61147317U (https=) 1985-03-05 1986-09-11
JPH0893441A (ja) * 1994-09-21 1996-04-09 Isuzu Motors Ltd 消音器
JP2002156977A (ja) * 2000-11-22 2002-05-31 Mitsubishi Heavy Ind Ltd 消音装置
JP2004252340A (ja) * 2003-02-21 2004-09-09 Toshiba Corp 分岐ダクト消音装置
JP2008064446A (ja) * 2006-08-07 2008-03-21 Denso Corp 車両空調用吹出ダクトおよび車両用空調装置
CN106015818A (zh) * 2016-07-06 2016-10-12 南京常荣声学股份有限公司 一种消声节能管道

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3242292A1 (en) * 2016-05-04 2017-11-08 Sontech International AB A sound damping device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61147317U (https=) 1985-03-05 1986-09-11
JPH0893441A (ja) * 1994-09-21 1996-04-09 Isuzu Motors Ltd 消音器
JP2002156977A (ja) * 2000-11-22 2002-05-31 Mitsubishi Heavy Ind Ltd 消音装置
JP2004252340A (ja) * 2003-02-21 2004-09-09 Toshiba Corp 分岐ダクト消音装置
JP2008064446A (ja) * 2006-08-07 2008-03-21 Denso Corp 車両空調用吹出ダクトおよび車両用空調装置
CN106015818A (zh) * 2016-07-06 2016-10-12 南京常荣声学股份有限公司 一种消声节能管道

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4610975A4

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JPWO2024090085A1 (https=) 2024-05-02
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US20250225967A1 (en) 2025-07-10
EP4610975A1 (en) 2025-09-03

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