JP2019207385A - Sound reduction device - Google Patents

Abstract

To reduce a wide range of propagation sounds of a desired frequency domain.SOLUTION: A sound reduction device (1) includes at least three diaphragms (2) faced across from one another along a direction crossing a propagation direction of a propagation sound, wherein: a particle velocity-increasing region appears along an edge of the diaphragm (2), wherein a particle velocity in the direction crossing the propagation direction of the propagation sound increases in the particle velocity-increasing region. The sound reduction device further includes a sound absorption layer (3) arranged in at least the particle velocity-increasing region, so that a vibrational energy based on the particle velocity in the direction crossing the propagation direction of the propagation sound in the particle velocity-increasing region is converted into a thermal energy.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sound reduction device using a sound absorbing layer that converts vibration energy based on particle velocity of propagating sound into heat energy.

  One of the typical methods for digging tunnels is the mountain method. In the mountain construction method, tunnels are dug horizontally using blasting by dynamite. In this case, the blasting sound of the bedrock may become an environmental problem.

  This blasting sound has many frequency components lower than several hundred Hz. Due to the blasting work, window glass of private houses etc. may vibrate and complain. Many of the causes are due to low frequency sound.

  The blasting sound during tunnel excavation is a shocking explosion near the sound source, but the sound in the middle and high frequency range is attenuated by soundproof doors installed at the wellhead, and the sound wave in the low frequency range is mainly used. The frequency of the low frequency region is related to the natural vibration frequency of window glass, joinery, etc., and may cause vibration of the joinery and rattling.

  For this reason, there is a demand for a sound reduction device that focuses on the low frequency region of the blasting sound. Low-frequency sound cannot be expected to have a great effect with ordinary porous sound-absorbing materials and sound-insulating materials (Non-Patent Document 1).

  Therefore, as such a sound reduction device, a sound reduction device for blasting sound of about 100 Hz or less has been developed by applying an acoustic principle such as a phase interference / resonator (Non-patent Documents 2-4).

Yasuo Inoue, “Trends in Tunnel Blowing Noise Countermeasures” Noise Control Vol.41, No.6 (2017) pp.253-257 Masato Kobayashi, et al., “Muffler for Ultra Low Frequency Sound Generated by Tunnel Blasting” Noise Control Vol.41, No.6 (2017) pp.258-261 Yasuhiro Honda et al., “Development and application of tunnel blast silencer using acoustic tube” Noise control Vol.41, No.6 (2017) pp.262-265 Tsutomu Tsunoda et al., “Silence silencer using resonance phenomenon of open tube” Noise control Vol.41, No.6 (2017) pp.266-267

  However, the sound reduction device using the phase interference / resonator as described above can only reduce the sound of a specific frequency in the low frequency region only at a pinpoint, and the sound in the low frequency region can be reduced over a wide range. There is a problem that the blast sound cannot be reduced because it cannot be reduced, and the sound reduction effect is not satisfactory.

  In addition to the blasting sound of tunnel construction, there is a strong demand for reducing the propagation sound in a desired frequency region over a wide range, for example, the propagation sound propagating in a duct pipe provided in the ceiling or air of an office building.

  An object of one embodiment of the present invention is to realize a sound reduction device that can greatly reduce a propagation sound in a desired frequency region in a wide range.

  In order to solve the above-described problem, a sound reduction device according to an aspect of the present invention includes at least three partition plates disposed to face each other along a direction intersecting a propagation direction of a propagation sound, A particle velocity increasing region in which the particle velocity in the intersecting direction of the propagating sound increases appears along the edge of the partition plate, and vibration energy based on the particle velocity in the intersecting direction in the particle velocity increasing region is converted into thermal energy. In order to convert, it further comprises a sound absorption layer disposed at least on the edge.

  According to one embodiment of the present invention, it is possible to realize a sound reduction device that can greatly reduce the propagation sound in a desired frequency region over a wide range.

(A) is a front schematic cross section of the sound reduction device according to Embodiment 1, and (b) is a side view thereof. (A) is a front schematic cross-sectional view showing the numerical analysis conditions of the particle velocity amplitude distribution in the tube of the sound reduction device, and (b) is a side view thereof. (A) (b) is a graph which shows the numerical analysis result based on the said numerical analysis conditions. (A)-(c) is a graph which shows the numerical analysis result which changed the said numerical analysis conditions. (A)-(d) is a graph which shows the numerical analysis conditions and numerical analysis result which concern on a comparative example. (A)-(d) is a graph which shows the numerical analysis conditions and numerical analysis result which concern on a modification. (A)-(d) is a graph which shows the numerical-analysis conditions and numerical-analysis result based on another comparative example. (A)-(d) is a graph which shows the numerical-analysis conditions and numerical-analysis result based on another modification. (A) is a figure for demonstrating the sound pressure regarding the sound absorption layer provided in the sound reduction apparatus, an average flow velocity, and a vibration speed, (b) is the tubular area | region used for a theoretical analysis, a thin rigid board, and a thin sound absorption layer. FIG. The sound reduction is a graph showing the attenuation of the level of propagation sound by the device, (a) shows the surface density of the sound absorbing layer shows the case of 1kg / m ^2, (b) the flow resistance of the backing layer is 1600 ns / shows the case of m ^3. (A) is a front schematic cross-sectional view of a sound reduction device according to a comparative example, (b) is a side view thereof, and (c) is an amount of attenuation of a propagation sound level by the sound reduction device according to the comparative example. It is a graph to show. (A) is a front schematic cross-sectional view of the sound reduction device according to the modified example, (b) is a side view thereof, and (c) is an attenuation of the level of the propagation sound by the sound reduction device according to the modified example. It is a graph to show. (A) is a front schematic cross-sectional view of a sound reduction device according to another modification, (b) is a side view thereof, and (c) is a level of sound propagated by the sound reduction device according to another modification. It is a graph which shows the amount of attenuation. (A) is a front schematic cross-sectional view of a sound reduction device according to still another modification, (b) is a side view thereof, and (c) is a propagation sound by the sound reduction device according to still another modification. It is a graph which shows the amount of attenuation of the level. (A) is a front schematic cross-sectional view of a sound reduction device according to still another modification, (b) is a side view thereof, and (c) is a propagation sound by the sound reduction device according to still another modification. It is a graph which shows the amount of attenuation of the level. (A) is a front schematic cross-sectional view of a sound reduction device according to still another modification, (b) is a side view thereof, and (c) is a propagation sound by the sound reduction device according to still another modification. It is a graph which shows the amount of attenuation of the level. (A) is a front schematic cross section of the sound reduction device according to the second embodiment, (b) is a plan view thereof, and (c) is a graph showing the attenuation of the level of the propagation sound by the sound reduction device. is there. (A) is a front schematic cross section of the sound reduction device according to the third embodiment, (b) is a side view thereof, and (c) is a graph showing the attenuation of the level of the propagation sound by the sound reduction device. is there. It is a figure which shows the external appearance of the said sound reduction apparatus. (A) is a perspective view which shows the external appearance of the sound reduction box provided in the sound reduction apparatus which concerns on Embodiment 4, (b) is a perspective view which shows the example of an arrangement | sequence of the said sound reduction box, (c) is It is a schematic cross section of the tunnel in which the said sound reduction box was installed.

  Hereinafter, embodiments of the present invention will be described in detail.

〔Overview〕
In the space where the propagation sound propagates, if there are a plurality of dents of appropriate size separated by a partition plate orthogonal to the propagation direction, the method of the opening surface near the partition plate forming the opening surface of this dent. Regions with large particle velocities appear concentrated in the linear direction. This means that a vibration velocity component perpendicular to the propagation direction is generated by the partition plate and the depression. The magnitude of the vibration velocity component orthogonal to the propagation direction may be 5 times or more larger than the vibration velocity component of the propagation sound propagating through the space, although it depends on the size of the recess.

  A thin porous sound-absorbing layer (hereinafter referred to as “sound-absorbing layer”) having appropriate physical characteristics and air permeability is installed in the vicinity of a region where vibration energy of a vibration velocity component orthogonal to the propagation direction is concentrated. As a result, when air particles that vibrate in the normal direction of the sound absorbing layer (direction orthogonal to the propagation direction of the propagating sound) pass through the sound absorbing layer, the sound is absorbed by the surface of the sound absorbing layer fibers or the void walls. Energy (vibration of air particles) is converted into thermal energy. As a result, numerical analysis shows that the propagation sound can be effectively suppressed.

  In each embodiment of the present application, conventional air column resonance, Helmholtz resonance, or the like is not used. In addition, there is a conventional method of lining a sound absorbing material that is often used for silencing air conditioning duct systems.

  However, each embodiment of the present application concentrates the vibration energy of the vibration velocity component orthogonal to the propagation direction in the vicinity of the partition plate forming the opening of the recess by combining the partition plate and the appropriate size recess. This is based on a new concept that is different from the above-described conventional method in that the sound is effectively absorbed by the sound absorbing layer parallel to the propagation direction having the proper physical characteristics. And according to each embodiment of this application, sound reduction performance can be improved greatly compared with the said conventional method, and the quantity of the sound-absorbing material to be used is also much less than the said conventional lining method.

  The conventional method of canceling sound by phase interference or a resonator can obtain an effect only in a specific narrow frequency band, whereas each embodiment of the present application has a high reduction in a wide frequency band including a low frequency band. It is also a great feature to demonstrate sound performance.

  The sound reduction device according to the first embodiment to be described later can be expected to have a great effect in silencing such as a low-frequency blast sound particularly in tunnel excavation work. Since the sound reduction device can be constituted by a panel-like member that can be easily assembled and disassembled, it is also suitable for construction sites that require frequent installation and removal as tunnel excavation proceeds. Moreover, after dismantling, there is an advantage that it can be stored compactly and can be easily transported.

  Further, as shown in the second embodiment to be described later, for the sound propagating along a flat surface, it is possible to suppress the propagation sound in the mid-high range by installing a similar device.

Embodiment 1
(Configuration of the sound reduction device 1)
FIG. 1A is a schematic front sectional view of a sound reduction device 1 according to Embodiment 1, and FIG. 1B is a side view thereof. The sound reduction device 1 is orthogonal to the propagation direction (x direction) of the propagation sound 10 propagating through the tubular space 4 formed inside the tubular body 9 having a rectangular cross section, and projects from the inner wall 11 of the tubular body 9 to face each other. 6 frame-shaped partition plates 2 are provided. Five adjacent annular recesses 6 are formed by the adjacent partition plate 2 and the inner wall 11.

  In the present specification, the “tubular body” means a tubular structure. The cross section is not limited to a circle, but may be a rectangle or other shapes. In addition, the “tubular body” includes a section whose cross section is not constant along the axial direction. A tunnel and other structures are also included in the “tubular body”.

  Each partition plate in which a particle velocity increasing region 7 in which the particle velocity of the propagation sound 10 along the normal direction (y direction in FIG. 1) of the opening surface of the depression formed by the recess 6 greatly increases protrudes from the inner wall 11. Appears along the tip of 2 (edge).

  The sound reduction device 1 includes a cylindrical sound absorbing layer 3 having a rectangular cross section in order to convert vibration energy based on the particle velocity in the normal direction of the opening surface of the depression corresponding to the particle velocity increasing region 7 into heat energy. The six partition plates 2 are connected to each other to cover the five annular recesses 6.

  The width d and the depth h of each recess 6 are set based on the minimum suppression frequency wavelength λ representing the wavelength corresponding to the minimum frequency to be suppressed of the propagation sound 10. The width d of the recess 6 is preferably λ / 5 or less. The depth h of the recess 6 is preferably λ / 30 or more.

  Three or more partition plates 2 may be provided, and two or more recesses 6 may be formed. It is preferable that three or more recesses 6 are formed. In order to attenuate the propagation sound 10 greatly, the more recesses 6 are better.

The surface density M and the flow resistance rs of the sound absorbing layer 3 are also set based on the minimum suppression frequency wavelength λ. The surface density M of the sound-absorbing layer 3 needs to be increased generally in proportion to the wavelength in the range of 0.25 to 20 kg / m ² according to the frequency band in which the propagation sound 10 is to be suppressed. In addition, the flow resistance rs is effective in a wide band around 1000 Ns / m ^3. However, if a value within a range of about 1/4 to 4 times is appropriately selected, the flow resistance rs is large with respect to the frequency band to be suppressed. effective.

  The sound absorbing layer 3 only needs to be provided so as to connect the tip of the partition plate 2 so as to cover the recess 6, and it is not necessary to fill the interior of the recess 6 with the sound absorbing material. Since the particle velocity increasing region 7 in which the particle velocity in the normal direction of the opening surface of the dent greatly increases appears at the tip of the partition plate 2, it is sufficient to provide the sound absorbing layer 3 only near the tip. There is no need to fill the interior of 6 with a sound absorbing material. Therefore, the propagation sound 10 can be efficiently reduced with very few sound absorbing materials.

  As the sound absorbing material constituting the sound absorbing layer 3, for example, cloth, glass wool, porous material, aluminum sintered material, and aluminum fiber material can be used.

  The partition plate 2 may not be provided so as to protrude from the inner wall 11 of the tubular body 9. For example, six partition plates 2 may be provided so that a gap is formed between the inner wall 11 and five recesses opening outward in the radial direction. In this case, the sound-absorbing layer 3 is provided so as to cover the five recesses that open outward in the radial direction by connecting the ends of the partition plate 2 on the inner wall 11 side. Further, five concave portions opening inward in the radial direction and five concave portions opening outward in the radial direction are provided, and the tip of the partition plate 2 opposite to the inner wall 11 is connected. Then, the sound absorbing layer 3 covering the five recesses opening inward in the radial direction and the tip of the partition plate 2 on the inner wall 11 side are connected, and the five recesses opening outward in the radial direction. You may comprise so that the sound absorption layer 3 which covers may be attached.

  The partition plate 2 may not be provided so as to protrude from the four sides of the rectangular cross section of the tubular body 9, and may be provided so as to protrude from at least one side of the rectangular cross section.

  The tubular body 9 does not have to have a rectangular cross section, for example, a circular cross section.

  By using the sound reduction device 1 composed of an assembly of the plurality of partition plates 2, the plurality of recesses 6, and the sound absorbing layer 3 (panel) in series, a greater attenuation effect of the propagation sound 10 can be obtained. Further, since the frequency band to be suppressed is widened by configuring each of the aggregate sound reduction devices 1 used in multiple stages in series to have different attenuation characteristics, the application field of the sound reduction device 1 is further expanded. It becomes possible.

  Both the partition plate 2 and the sound absorbing layer 3 of the sound reduction device 1 can be disassembled into a panel shape. Accordingly, since the sound reduction device 1 becomes very small when disassembled, it is easy to move and store, unlike a conventional sound reduction device using a phase interference / resonator.

(Numerical analysis of pipe particle velocity amplitude distribution)
FIG. 2A is a schematic front sectional view showing a numerical analysis condition of the particle velocity amplitude distribution in the tube of the sound reduction device 1, and FIG. 2B is a side view thereof. 3A and 3B are graphs showing the numerical analysis results based on the numerical analysis conditions. For convenience of explanation, members having the same functions as those described above are denoted by the same reference numerals, and the description thereof will not be repeated.

  Numerical analysis of the particle velocity amplitude distribution in the y direction based on the propagating sound 10 propagating through the tubular space 4 is performed on the numerical analysis region R in the XY plane (Z = 0) shown in FIG. went. Numerical analysis was performed on the basis of the wave equation and boundary conditions, and was carried out with actual dimensional numerical values on the order of 1/10 to 1/20. For example, numerical analysis is performed with numerical values such as the horizontal dimension a = 0.5 m, the vertical dimension b = 0.5 m, the depth h = 0.1 m of the recess 6 and the width d = 0.1 m of the recess 6 of the cross section of the tubular body 9 Went.

  When the frequency of the propagating sound 10 is 250 Hz, six very large particle velocities in the y direction appear corresponding to positions near the edges of the six partition plates 2 as shown in FIG. . Even when the frequency of the propagating sound 10 was 500 Hz, a very large particle velocity in the y direction appeared with the same tendency as shown in FIG.

  When the sound absorbing layer 3 (FIG. 1) including, for example, a fiber material having a large surface area is disposed along the x direction in the vicinity of the edge of the partition plate 2 where the particles vibrate vigorously in the y direction in this way, It is considered that frictional force is generated in proportion to the particle velocity, and vibration energy based on the particle velocity in the y direction can be efficiently converted into thermal energy.

4A to 4C are graphs showing numerical analysis results obtained by changing the numerical analysis conditions.
When the number of the partition plates 2 is four and the number of the recesses 6 is three, the large particle velocity in the y direction is four corresponding to the positions of the four partition plates 2 as shown in FIG. Appeared. When the number of the recesses 6 is 5, six large particle velocities in the y direction appear corresponding to the positions of the six partition plates 2 as shown in FIG. When the number of the recesses 6 was 8, nine large particle velocities in the y direction appeared corresponding to the positions of the nine partition plates 2 as shown in FIG. The frequency of the propagating sound 10 was 500 Hz in all cases.

  Thus, a region having a very large particle velocity amplitude in the y direction appeared along the edges of the partition plates 2 installed in a plurality.

  5A to 5D are graphs showing numerical analysis conditions and numerical analysis results according to the comparative example. For convenience of explanation, members having the same functions as those described above are denoted by the same reference numerals, and the description thereof will not be repeated.

  As shown in FIGS. 5 (a) and 5 (b), when two partition plates 2 are provided and the number of the recesses 6 is set to one without partitioning the two partition plates 2, FIG. ) As shown in (d), a large particle velocity in the y direction corresponding to the position of the partition plate 2 hardly appeared. For this reason, the partition plate 2 is further provided between the two partition plates 2 to partition the partition plate 2 and the number of the recesses 6 is plural, so that a very large particle velocity in the y direction can be obtained near the edge of the partition plate 2. It is thought to appear at the position.

  6A to 6D are graphs showing numerical analysis conditions and numerical analysis results according to the modification. As shown in FIG. 6 (a), even if the interval between the adjacent partition plates 2 is ½ that of the example shown in FIG. 2, as shown in FIGS. 6 (c) and 6 (d), a large particle velocity in the y direction. Appeared in the same tendency corresponding to the position of the partition plate 2. The frequency of the propagation sound 10 was 500 Hz.

  7A to 7D are graphs showing numerical analysis conditions and numerical analysis results according to another comparative example. As shown in FIGS. 7A and 7B, when the interval between adjacent partition plates 2 is halved in the same manner as in the example of FIG. 6, and the depth of the recess 6 is halved in the example of FIG. In addition, a large particle velocity in the y direction corresponding to the position of the partition plate 2 did not appear. Thus, when the depth dimension of the recess 6 is small, the phase difference is small, and a very large particle velocity in the y direction does not occur. For this reason, in order to generate a very large particle velocity in the y direction, it is considered that an appropriate depth of the recess 6 is necessary in relation to the wavelength corresponding to the frequency of the propagation sound 10 to be suppressed. .

  8A to 8D are graphs showing numerical analysis conditions and numerical analysis results according to another modification. Even if the spacing between adjacent partition plates 2 is unequal as shown in FIG. 8 (a), the large particle velocity in the y direction has the same tendency as shown in FIGS. 8 (c) and 8 (d). Appeared corresponding to position 2. Width d = 0.1 m, Width d1 = 0.05 m, Width d2 = 0,07 m, Width d3 = 0.03 m, Width d4 = 0.05 m, Width d5 = 0.12 m, Width d6 = 0.08 m Numerical analysis was performed. Thus, even when the partition plates 2 are not arranged at equal intervals, the tendency that a large particle velocity in the y direction appears corresponding to the position of the partition plate 2 is the same.

(Theoretical treatment of sound absorbing layer 3)
FIG. 9A is a diagram for explaining the sound pressure, the average flow velocity, and the vibration velocity regarding the sound absorbing layer 3 provided in the sound reduction device 1, and FIG. 9B is a tubular region and a thin rigid plate used for theoretical analysis. It is a figure which shows a thin sound absorption layer. The theoretical handling of the sound absorbing layer 3 that converts vibration energy based on the particle velocity in the y direction into heat energy will be described.

In FIG. 9A, the sound absorbing layer 3 is a thin air-permeable porous layer. The sound pressures acting on both surfaces of the sound absorbing layer 3 are defined as p ₁ and p ₂ . And let the average flow velocity of the particles of the propagating sound passing through the sound absorbing layer 3 be v _s . The vibration speed of the sound absorption layer 3 and v _m.

As shown in FIG. 9 (a), in the porous sound absorbing layer 3 that is sufficiently thin compared to the wavelength, has a negligible thickness, and has air permeability, the flow resistance is rs, and the sound pressures on both sides of the sound absorbing layer 3 are respectively set. Let p ₁ , p ₂ , and the velocity of air particles passing through the sound absorbing layer 3 be v _s ,

There is a relationship. The sound absorbing layer 3 is also excited by a sound pressure difference between the sound pressure p ₁ and the sound pressure p ₂ acting on both sides. When M is the surface density of the sound absorbing layer 3, v _m is the vibration velocity, and exp (−iωt) is used as a time term, the following equation is obtained.

Therefore, the particle velocity v of the surface of the backing layer 3 is represented by the sum of both the velocity v _s and the vibration velocity v _m of the air particles,

It becomes. When − (p ₁ −p ₂ ) / v = Z _r (impedance of the sound absorbing layer 3) is set,

  Referring to FIG. 9 (b), a tubular region Ω used for theoretical analysis, a thin rigid plate B existing in the tubular region Ω, and a thin sound absorbing layer C are shown.

  Both ends of the tube are non-reflective ends A (impedance is ρc), and a plurality of point sound sources Ps arranged at equal intervals on a plane orthogonal to the axis and the surface direction n (normal) are shown in FIG. Is shown in

  As shown in FIG. 9B, in a tubular region Ω including a plurality of point sound sources Ps, a thin rigid plate B, and a thin sound absorbing layer C, the non-reflecting ends A at both ends of the tube do not reflect incident sound waves. Thus, it is assumed that the boundary has an impedance of ρc. Where ρ is the density of air and c is the speed of sound. In addition, a plane wave is approximately generated in the tube by a plurality of point sound sources Ps arranged uniformly in a plane orthogonal to the axis.

  Applying the integral formula derived from the wave equation to the tubular region Ω, the velocity potential φ is

  Reference 1) relating to the normal differential equation is “T. terai: On calculation of sound fields around three dimensional objects by interal equation methods, J. Sound & Vib., 69, 71-100, 1980”. It is.

In Equation (9), φ and Φ on the boundary can be obtained by simultaneously solving the integral equation in which P is converged on the surface A or S and the integral equation of Equation (11) and Equation (12). . The sound pressure distribution at a point in the space can be obtained by substituting the value on the solved boundary into the equation (9) and the particle velocity into the equation (10) ( _np is the x, y, z direction). Each component can be obtained by using a unit vector of If there is no object such as a sound reduction device in the middle of the pipe with no cross-sectional change, the sound radiated from the sound source in both directions of the pipe is not attenuated and reaches the non-reflection end A as it is. The time average energy flow I of the sound passing through the non-reflecting end A is obtained by using the sound pressure p and the particle velocity v on the non-reflecting end A of the boundary obtained above

It can be expressed. However, _{S A} is Kandan area, * represents a complex conjugate. As shown in FIG. 9B, when an object having a sound absorbing layer C is installed in the middle of the tube, the effect of the object (sound reduction device) is that energy passing through the right non-reflective end A before and after installation. Can be obtained by comparing.

  Various numerical solutions for boundary integral equations are conceivable, but the boundary element method is used here.

(Attenuation of the level of the propagation sound 10)
FIG. 10 is a graph showing the amount of attenuation of the level of the propagation sound 10 by the sound reduction device 1. FIG. 10A shows the case where the surface density M of the sound absorbing layer 3 is 1 kg / m ² , and FIG. 10B shows the sound absorbing layer. 3 shows a case where the flow resistance rs 3 is 1600 Ns / m ³ . The horizontal axis indicates the frequency of the propagation sound 10 and the vertical axis indicates the amount of attenuation of the propagation sound 10 level.

When the surface density M of the sound absorbing layer 3 provided in the sound reduction device 1 is 1 kg / m ² , the flow resistance rs of the sound absorbing layer 3 is 100 Ns / m ³ , 200 Ns / m ³ , 400 Ns / m ³ , 800 Ns / m. FIG. 10A shows the attenuation amount of the level of the propagation sound 10 when it is changed to ³ , 1600 Ns / m ³ , 3200 Ns / m ³ , and 6400 Ns / m ³ .

When the flow resistance rs of the sound absorbing layer 3 provided in the sound reduction device 1 is 1600 Ns / m ³ , the surface density M of the sound absorbing layer 3 is 16 kg / m ² , 8 kg / m ² , 4 kg / m ² , 2 kg. FIG. 10B shows the attenuation amount of the level of the propagation sound 10 when it is changed to / m ² , 1 kg / m ² , 0.5 kg / m ² , and 0.25 kg / m ² .

  10 (a) and 10 (b), the level is attenuated over a wide range of a low frequency region by about 10 dB to 15 dB by the sound reduction device 1 of the first embodiment shown in FIG. I can see it.

  FIG. 11A is a schematic front sectional view of a sound reduction device according to a comparative example, FIG. 11B is a side view thereof, and FIG. 11C is a diagram illustrating the level of the propagation sound 10 by the sound reduction device according to the comparative example. It is a graph which shows attenuation amount.

  FIGS. 11A and 11B correspond to the configuration of the non-partitioned recess 6 described above with reference to FIGS. In the configuration in which the number of the recesses 6 is one without dividing the partition plate 2 between the two partition plates 2, the case of FIG. Compared with the attenuation performance, the attenuation performance was greatly reduced as shown in FIG.

  FIG. 12A is a schematic front sectional view of a sound reduction device according to a modification, FIG. 12B is a side view thereof, and FIG. 12C is a diagram showing the level of the propagation sound 10 by the sound reduction device according to the modification. It is a graph which shows attenuation amount.

  12 (a) and 12 (b) correspond to the configuration of the recess 6 in which the interval between the partition plates 2 described above with reference to FIG. 6 is narrowed. Even if the interval between the partition plates 2 is narrower than the configuration shown in FIG. 1, the attenuation characteristics are almost the same as shown in FIG.

  FIG. 13A is a schematic front sectional view of a sound reduction device according to another modification, FIG. 13B is a side view thereof, and FIG. 13C is a propagation sound by the sound reduction device according to the other modification. It is a graph which shows the attenuation amount of 10 levels.

  FIGS. 13A and 13B correspond to the configuration of the recesses 6 in which the partition plates 2 described above with reference to FIGS. 8A and 8B are arranged at unequal intervals. Even when the arrangement of the partition plates 2 was changed from the equal interval shown in FIG. 1 to the unequal interval, there was no significant change in the attenuation characteristics as shown in FIG. 13 (c).

  FIG. 14A is a schematic front sectional view of a sound reduction device according to still another modification, FIG. 14B is a side view thereof, and FIG. 14C is the sound reduction device according to still another modification. 4 is a graph showing the amount of attenuation of the level of the propagation sound 10;

  14 (a) and 14 (b) show a configuration of still another modified example in which the partition plate 2 is changed into a shape protruding only from the left and right inner walls 11 and the upper inner wall 11 in consideration of use in the tunnel. Show. Even if the partition plate 2 is changed to a shape that is intended for use in a tunnel, as shown in FIG. 14C, if the physical characteristics of the sound absorbing layer 3 are appropriately selected, large attenuation can be obtained in a wide frequency range. It is done. For example, the tubular space 4 is a tunnel, and the propagation sound 10 is a blast sound generated in tunnel construction.

  FIG. 15A is a schematic front sectional view of a sound reduction device according to still another modification, FIG. 15B is a side view thereof, and FIG. 15C is the sound reduction device according to still another modification. 4 is a graph showing the amount of attenuation of the level of the propagation sound 10;

  As shown in FIGS. 15A and 15B, the recess 6 may be formed outward in the radial direction from the inner wall 11. The tubular body 9 </ b> B has an inner wall 11 </ b> B that is formed radially outward from the inner wall 11. Four partition plates 2 </ b> B are provided so as to protrude from the inner wall 11 </ b> B inward in the radial direction to a position corresponding to the inner wall 11. Five concave portions 6 are formed by the four partition plates 2B and the step between the inner wall 11 and the inner wall 11B of the tubular body 9B. Also in this case, as shown in FIG. 15C, if the physical characteristics of the sound absorbing layer 3 are appropriately selected, large attenuation can be obtained in a wide frequency range.

  FIG. 16A is a schematic front sectional view of a sound reduction device according to still another modification, FIG. 16B is a side view thereof, and FIG. 16C is the sound reduction device according to still another modification. 4 is a graph showing the amount of attenuation of the level of the propagation sound 10;

When the numerical analysis is performed with the scale being 10 times under the conditions shown in FIGS. 1 and 2, the surface density M is 10.0 kg / m ^{2 which} is 10 times that of the example shown in FIG. As shown in FIG. 16 (c), substantially the same attenuation characteristics as in FIG. 10 (a) were obtained. The value of the frequency of the propagation sound 10 on the horizontal axis is (1/10) times that of the example shown in FIG.

As shown in FIG. 16A, the broken line C1 indicates that the sound absorbing material 93 (glass wool 32 kg / m ³ ) is placed in the recess 6 having a section width between the leftmost partition plate 2 and the rightmost partition plate 2. Represents the predicted calculation value when filled.

  As shown in FIG. 16 (c), the present embodiment is superior in a frequency band important for suppressing blasting sound and the like as compared with the method using the normal porous sound absorbing material 93 indicated by the broken line C1. Demonstrate the effect. Further, in the present embodiment, the amount of the sound absorbing material to be used is much smaller than the method indicated by the broken line C1.

  The tubular space 4 of the sound reduction device 1 according to the first embodiment is a tunnel, for example, and the propagation sound 10 is a blasting sound generated, for example, in tunnel construction.

  The sound reduction device 1 according to the first embodiment can be applied, for example, to the reduction of propagation sound propagating in a duct provided in an air conditioner or a muffler of an automobile.

  Further, the sound reduction device 1 radiates the compression wave generated by the high-speed train entering the tunnel as a bursting aerial sound based on the pulsed pressure wave from the opposite exit through the tunnel. In order to reduce the generated micro-pressure wave, it can be applied to the entrance and exit of a tunnel having a passage portion through which a high-speed train passes.

[Embodiment 2]
Another embodiment of the present invention will be described below. For convenience of explanation, members having the same functions as those described in the above embodiment are given the same reference numerals, and the description thereof will not be repeated.

  FIG. 17A is a schematic front sectional view of the sound reduction device 1A according to the second embodiment, FIG. 17B is a plan view thereof, and FIG. 17C is the attenuation of the level of the propagation sound 10 by the sound reduction device 1A. It is a graph which shows quantity.

  In Embodiment 1 mentioned above, the example which arrange | positions the partition plate 2 inside the tubular body 9 was shown. However, the present invention is not limited to this. Also for the propagation sound 10 propagating along the flat surface, by installing the partition plate 2C as shown in FIGS. 17A and 17B, as shown in FIG. Can suppress mid-high range.

  The sound reduction device 1A includes a plurality of rectangular partition plates 2C provided to protrude from the flat surface 12 in a direction orthogonal to the propagation direction of the propagation sound 10 propagating from the point sound source Ps along the flat surface 12. . A part of the plurality of partition plates 2C is arranged along a direction parallel to the flat surface 12 and perpendicular to the propagation direction of the propagation sound 10, and the remaining part of the plurality of partition plates 2C is the propagation sound 10 Are arranged so as to be orthogonal to some of the plurality of partition plates 2C along the propagation direction. In this way, the plurality of partition plates 2C are arranged in a lattice pattern.

  A sound absorbing layer 3A is provided in the sound reduction device 1A so as to cover the respective tips of the plurality of partition plates 2C and the plurality of recesses 6 surrounded by the adjacent partition plates 2C.

  Accordingly, the sound reduction device 1A can suppress the propagation sound 10 propagating along the flat ground surface. According to the sound reduction device 1A, it is possible to attenuate the propagation sound 10 while keeping a view of the propagation direction of the propagation sound 10 without installing a sound insulation wall.

  And since the some partition plate 2C is arrange | positioned at a grid | lattice form, the propagation sound which propagates in the arbitrary directions along the flat surface 12 can be suppressed.

[Embodiment 3]
Still another embodiment of the present invention will be described below. For convenience of explanation, members having the same functions as those described in the above embodiment are given the same reference numerals, and the description thereof will not be repeated.

  FIG. 18A is a schematic front sectional view of the sound reduction device according to the third embodiment, FIG. 18B is a side view thereof, and FIG. 18C shows the attenuation amount of the level of the propagation sound 10 by the sound reduction device. It is a graph to show. FIG. 19 is a diagram showing the appearance of the sound reduction device.

  A model experiment for verifying the numerical analysis results performed in the first and second embodiments was performed. As shown in FIG. 18 (a), a 16 cm diameter speaker 14 for filling the sound absorbing material and generating the propagation sound 10 is arranged in the −x direction of the sound reduction device 1 described in the first embodiment. In the x direction of the sound device 1, a microphone 15 for measuring the sound pressure of the propagation sound 10 and a sound absorbing layer 16 that functions as a non-reflective end are arranged.

For the thin sound-absorbing layer 3, Indian cotton having a flow resistance of rs = 506 Ns / m ³ and a surface density of M = 0.32 kg / m ² was used. In the measurement, an M-sequence signal is generated from the propagation sound 10 generated from the speaker 14, and the level difference of the propagation sound 10 due to the presence or absence of the suppression structure according to the sound reduction device 1 of the first embodiment is calculated using a correlation method using the M-sequence signal. Was measured.

  As shown in FIG. 18C, the curve C2 representing the measurement result shows a tendency similar to the curve C3 representing the numerical analysis result. Considering that the influence of standing waves due to slight reflected waves at both ends of the tubular body 9 cannot be ignored and that approximation of plane wave propagation is difficult to achieve at frequencies exceeding 1 kHz, the measurement results and numerical analysis results are good. This is considered to indicate a match.

[Embodiment 4]
In the above-described embodiment, the example of the configuration in which the partition plate protrudes from the inner wall is shown, but the present invention is not limited to this. In a large-scale space such as a tunnel, for example, a box-shaped object may be created with rectangular panels, and a large number of sound absorbing panel units may be arranged on one side in the horizontal and vertical directions.

  FIG. 20A is a perspective view showing an appearance of the sound reduction box 13 provided in the sound reduction device according to the fourth embodiment, and FIG. 20B is a perspective view showing an arrangement example of the sound reduction boxes 13. (C) is a schematic cross-sectional view of a tunnel in which the sound reduction box 13 is installed.

  The sound reduction device according to the fourth embodiment includes a cubic sound reduction box 13. The sound reduction box 13 includes a square bottom panel 24, four square elevation panels 25 erected from four sides of the bottom panel 24, and a sound absorbing panel 26 that covers an opening formed by the elevation panel 25. And have.

  For example, as shown in FIG. 20 (b), the sound reduction box 13 configured in this manner is in a matrix shape such that the elevation panel 25 forms the partition plate 2 and the sound absorption panel 26 forms the sound absorption layer 3. Placed in.

  As shown in FIG. 20 (c), the tunnel for carrying out the tunnel blasting work is arranged in the center so that the carry-in / carry-out passage 17 is covered with an inner wall 19 having a substantially semicircular cross section, and a ventilation duct. 18 is arranged near the inner wall 19. A plurality of sound reduction box clusters 27 are arranged so as to face the loading / unloading passage 17 with the sound absorbing layer 3 facing inward, and a plurality of sound reducing layers 3 face the inner wall 19 with the sound absorbing layer 3 facing outward. Arranged.

(Summary)
In order to solve the above-described problem, a sound reduction device according to an aspect of the present invention includes at least three partition plates disposed to face each other along a direction intersecting a propagation direction of a propagation sound, A particle velocity increasing region where the particle velocity in the intersecting direction of the propagating sound increases appears along the edge of the partition plate, and vibration energy based on the particle velocity in the intersecting direction of the particle velocity increasing region is converted into thermal energy. In order to convert, it further comprises a sound absorption layer disposed at least on the edge.

  In the sound reduction device according to one aspect of the present invention, it is preferable that the propagation sound propagates through the tubular space, and the partition plates are provided to face each other along a direction intersecting an inner wall forming the tubular space. .

  In the sound reduction device according to one aspect of the present invention, it is preferable that the sound absorbing layer is disposed at least on an end surface of a front end of the partition plate.

  In the sound reduction device according to one aspect of the present invention, it is preferable that the sound absorption layer is provided so as to connect the edges of the partition plate.

  In the sound reduction device according to one aspect of the present invention, the width and depth of the recess formed by the inner wall and the partition plate adjacent to the inner wall represent a wavelength corresponding to the minimum frequency at which the propagation sound is to be suppressed. It is preferable to set based on the suppression minimum frequency wavelength.

  In the sound reduction device according to one aspect of the present invention, the surface density and the flow resistance of the sound absorbing layer are set based on a suppression minimum frequency wavelength representing a wavelength corresponding to the minimum frequency to be suppressed of the propagation sound. It is preferable.

  In the sound reduction device according to one aspect of the present invention, it is preferable that the tubular space includes a tunnel, and the propagation sound includes a blast sound generated in tunnel construction.

In the sound reduction device according to one aspect of the present invention, the partition plate is disposed in a hollow space formed to be recessed outward in the radial direction from the inner wall of the tubular space,
It is preferable that a radially inner end of the partition plate is disposed along an inner wall of the tubular space.

  In the sound reduction device according to one aspect of the present invention, it is preferable that the propagation sound propagates along a flat surface, and the partition plate protrudes in a direction intersecting the flat surface.

  In the sound reduction device according to one aspect of the present invention, the partition plate is disposed in a hollow space formed to be recessed from the flat surface, and a tip of the partition plate is disposed along the flat surface. preferable.

  In the sound reduction device according to one aspect of the present invention, it is preferable that the partition plates are arranged in a lattice shape when viewed from a direction intersecting the propagation direction of the propagation sound.

  A sound reduction device according to an aspect of the present invention includes a polygonal bottom panel, a plurality of elevation panels erected from each side of the bottom panel, and a sound absorbing panel that covers an opening formed by the elevation panel It is preferable that a plurality of the sound reduction boxes are arranged so that the vertical panel of the sound reduction box having the above structure constitutes the partition plate and the sound absorption panel constitutes the sound absorption layer.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Sound reduction device 2 Partition board 3 Sound absorption layer 4 Tubular space 6 Recessed part 7 Particle velocity increase area 9 Tubular body 10 Propagation sound 11 Inner wall 12 Flat surface 13 Sound reduction box 24 Bottom panel 25 Elevation panel 26 Sound absorption panel 27 Noise reduction box cluster 93 Sound Absorbing Material λ Suppression Minimum Frequency Wavelength v Particle Speed M Surface Density rs Flow Resistance d Width h Depth R Numerical Analysis Area

Claims (12)

Comprising at least three partition plates arranged opposite to each other along a direction intersecting the propagation direction of the propagation sound,
A particle velocity increasing region in which the particle velocity in the intersecting direction of the propagation sound increases appears along the edge of the partition plate,
In order to convert the vibration energy based on the particle velocity in the intersecting direction of the particle velocity increasing region into thermal energy, the sound reduction device further includes a sound absorbing layer disposed at least on the edge. The propagation sound propagates through the tubular space;
The sound reduction device according to claim 1, wherein the partition plates are provided to face each other along a direction intersecting with an inner wall forming the tubular space.   The sound reduction device according to claim 2, wherein the sound absorbing layer is disposed at least on an end face of a tip of the partition plate.   The sound reduction device according to claim 1, wherein the sound absorbing layer is provided so as to connect each edge of the partition plate.   The width and depth of a recess formed by the inner wall and the partition plate adjacent to the inner wall are set based on a suppression minimum frequency wavelength representing a wavelength corresponding to a minimum frequency to be suppressed of the propagation sound. 2. The sound reduction device according to 2.   The sound reduction device according to claim 1, wherein the surface density and flow resistance of the sound absorbing layer are set based on a suppression minimum frequency wavelength representing a wavelength corresponding to a minimum frequency to be suppressed of the propagation sound. The tubular space includes a tunnel;
The sound reduction device according to claim 2, wherein the propagation sound includes a blasting sound generated in tunnel construction. The partition plate is disposed in a hollow space formed to be recessed radially outward from an inner wall of the tubular space;
The sound reduction device according to claim 2, wherein a radially inner end of the partition plate is disposed along an inner wall of the tubular space. The propagation sound propagates along a flat surface;
The sound reduction device according to claim 1, wherein the partition plate is provided so as to protrude in a direction intersecting with the flat surface. The partition plate is disposed in a hollow space formed by being recessed from the flat surface;
The sound reduction device according to claim 9, wherein a leading end of the partition plate is disposed along the flat surface.   The sound reduction device according to claim 1, wherein the partition plates are arranged in a lattice shape when viewed from a direction intersecting a propagation direction of the propagation sound.   The elevation panel of the sound reduction box having a polygonal bottom panel, a plurality of elevation panels erected from each side of the bottom panel, and a sound absorbing panel covering an opening formed by the elevation panel. The sound reduction device according to claim 1, wherein a plurality of the sound reduction boxes are arranged so as to constitute the partition plate and the sound absorption panel constitutes the sound absorption layer.