JP2021124701A - Low frequency sound reducing structure of tube body - Google Patents

Abstract

To provide a low frequency sound reducing structure of a tube body that can reliably reduce low frequency sound while ensuring circulation of gas.SOLUTION: Provided is a low frequency sound reducing structure of a tube body 10 whose both ends in the longitudinal direction are open. A first end 11 of the tube body 10 is provided with a sound absorption member 20. The sound absorption member 20 allows passage of gas at the first end 11. The low frequency sound reducing structure of the tube body 10 reduces acoustic particle velocity at c/2L (Hz) to c/2D (Hz) (herein, c: sound speed (m/s), L: length (m) of the tube body 10, and D: a tube body cross-sectional width determined by a cross-sectional shape of the tube body 10).SELECTED DRAWING: Figure 2

Description

The present invention relates to a low frequency sound reduction structure of a tubular body.

Buildings are usually equipped with a large number of pipes. The pipe body is also used as piping for air conditioners and ventilation fans. In particular, sound waves easily propagate in a tube for the purpose of gas circulation.

Therefore, an object of the present invention is to provide a low-frequency sound reduction structure of a tube body capable of reliably reducing low-frequency sound while ensuring gas flow.

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

[1] One aspect of the low frequency sound reduction structure of the tubular body according to the present invention is
It is a low-frequency sound reduction structure of a tube with both ends open in the longitudinal direction.
It has a sound absorbing member at one end of the pipe body, and has a sound absorbing member.
The sound absorbing member allows the passage of gas at the end and
The low frequency sound reduction structure of the tube is characterized by reducing the acoustic particle velocity of c / 2L (Hz) to c / 2D (Hz).
(Here, c: sound velocity (m / s), L: pipe length (m), D: pipe cross-sectional width determined by the cross-sectional shape of the pipe)

According to one aspect of the low-frequency sound reduction structure of the tube, the sound-absorbing member is provided at the open end where the acoustic particle velocity increases in the tube, so that low-frequency sound can be produced while ensuring the flow of gas. It can be surely reduced.

[2] In one aspect of the low frequency sound reduction structure of the tube,
The sound absorbing member may contain activated carbon.

According to one aspect of the low-frequency sound reduction structure of the tube, low-frequency sound can be reliably reduced while ensuring gas flow, and further has a deodorizing effect.

According to the low-frequency sound reduction structure of the tube body according to the present invention, low-frequency sound can be reliably reduced while ensuring the flow of gas.

It is a schematic diagram explaining the particle velocity of a tube body. It is a vertical cross-sectional view of the pipe body which concerns on this embodiment. It is a schematic diagram of the tube body which concerns on the modification. It is a perspective view which shows typically the double skin.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unreasonably limit the content of the present invention described in the claims. Moreover, not all of the configurations described below are essential constituent requirements of the present invention.

The low-frequency sound reduction structure of the tubular body according to the embodiment of the present invention is a low-frequency sound reduction structure of the tubular body in which both ends in the longitudinal direction are open, and a sound absorbing member is attached to one end of the tubular body. The sound absorbing member allows the passage of gas at the end,
The low frequency sound reduction structure of the tube is characterized by reducing the acoustic particle velocity of c / 2L (Hz) to c / 2D (Hz).
(Here, c: sound velocity (m / s), L: pipe length (m), D: pipe cross-sectional width determined by the cross-sectional shape of the pipe)

1. 1. Particle Velocity of Tube Body The particle velocity of the tube body 10 will be described with reference to FIG. FIG. 1 is a schematic view illustrating the particle velocity of the tube body 10. In FIG. 1, the cylindrical tube body 10 is shown in a vertical cross section, the magnitude of the acoustic particle velocity in the tube body 10 is represented by a solid line, and the magnitude of the sound pressure is represented by a broken line.

The tubular body 10 shown in FIGS. 1A and 1B has both ends open in the longitudinal direction. The tubular body 10 may have a cylindrical shape, for example, or may have a rectangular cross section.

Sound pressure can be perceived by humans, but acoustic particle velocity is difficult to grasp because humans cannot perceive it. As is clear from the curve shown by the broken line in FIG. 2, the sound pressure is the smallest at both ends of the tube body 10.

Since the acoustic particle velocity in the tube body 10 in which both ends are open deviates by 1/4 wavelength from the magnitude of the sound pressure in the tube body 10, the acoustic particle velocity in the opening first end portion 11 and the second end portion 12 is high. It becomes the maximum. The waveforms of the acoustic particle velocities in the case of different frequencies from (a) and (b) of FIG. 1 are shown. As described above, the positions where the acoustic particle velocities are maximized are both ends of the tube 10 even at different frequencies. Further, the positions where the acoustic particle velocities are maximized are both ends even if the pipe bodies 10 have different lengths.

2. Low-frequency sound reduction structure of the tube The low-frequency sound reduction structure of the tube 10 will be described with reference to FIG. FIG. 2 is a vertical cross-sectional view of the tubular body 10 in which both ends in the longitudinal direction according to the present embodiment are open.

As shown in FIG. 2, the pipe body 10 has a sound absorbing member 20 at a first end portion 11 which is one end portion. The second end portion 12, which is the other end portion, is open to the outside, and an opening is formed.

The pipe body 10 is, for example, a duct for ventilation, which is piped to a building. The duct is made of metal, for example. A ventilation fan may be provided at the second end portion 12. When the sound absorbing member 20 is arranged at the second end 12 where the ventilation fan is provided, the sound absorbing member 20 is arranged at the outer opening of the ventilation fan itself as the second end 12.

As described with reference to FIG. 1, the positions where the acoustic particle velocity is maximized in the tube body 10 having both ends open are the first end portion 11 and the second end portion 12. Since the acoustic particle velocity is the kinetic energy of air, which is a sound transmitter, if the motion of air can be hindered at the position where the acoustic particle velocity is maximum, the sound propagation in the tube 10 can be efficiently attenuated. The present inventors considered. Of course, there are positions in the tube 10 where the acoustic particle velocity is maximum other than both ends, but it is difficult to measure the position where the acoustic particle velocity is maximum for each tube 10. Therefore, the present inventors have decided to efficiently reduce low-frequency sound by arranging sound absorbing members 20 at at least one of both ends where the acoustic particle velocity in the tube body 10 is always maximized.

Since low-frequency sound may be generated from the equipment connected to the duct in the building, it is desirable to reduce the low-frequency sound by the sound absorbing member 20. The pipe body 10 is not limited to the duct. It is desirable to apply the present invention as long as the tube body 10 has an end portion that opens to a low-frequency sound source.

The sound absorbing member 20 allows the passage of gas at the first end 11 where the sound absorbing member 20 is installed. Since the tubular body 10 normally secures the flow of gas, it is desirable that the gas flow between the inside and the outside of the tubular body 10 is ensured even if the sound absorbing member 20 is provided at the first end portion 11. Is done. In order for the sound absorbing member 20 to allow the passage of gas, the sound absorbing member 20 is provided with a communication hole for communicating the outside and the inside of the pipe body 10. The minimum diameter of the communication holes and the number of communication holes are preferably such that the air permeability that can be tolerated in the application of the pipe body 10 can be ensured.

As shown in FIG. 2, the “first end portion 11” and the “second end portion 12” include the vicinity of the opening end that is slightly inside the tube body 10 from the opening end. Since the acoustic particle velocity gradually decreases toward the inside from the opening end, it is preferable that the sound absorbing member 20 is closer to the opening end in order to efficiently reduce low-frequency sound. However, depending on the attachment relationship with other members, it may be necessary to attach the sound absorbing member 20 slightly inside the pipe body 10 from the opening end.

The sound absorbing member 20 includes at least the first sound absorbing material 22, and may further include the second sound absorbing material 24. The first sound absorbing material 22 and the second sound absorbing material 24 have a function of converting the sound incident inside into heat by vibrating the air and viscous, a function of converting the sound into heat by friction between the air and the sound absorbing material, and the like. Reduces the energy of sound. As the first sound absorbing material 22 and the second sound absorbing material 24, glass wool, rock wool, a porous body, or the like can be adopted. Since glass wool and rock wool have low air permeability, it is preferable to provide a large vent. For example, a modified example described later can be considered. The sound absorbing member 20 preferably contains activated carbon as the first sound absorbing material 22. Activated carbon is a porous body. Low frequency sound can be reduced by the large number of minute holes on the surface of the activated carbon. Further, since the activated carbon is fine particles and the individual activated carbons are not connected to each other, it has a large number of fine communication holes for ensuring the flow of gas. Furthermore, activated carbon also has a deodorizing effect.

The first sound absorbing material 22 is provided so as to cover the entire opening of the first end portion 11 of the pipe body 10. The first sound absorbing material 22 has a disk shape having the same outer shape as the inner diameter of the pipe body 10. The first sound absorbing material 22 accommodates, for example, a plurality of sachets filled with activated carbon in a disk-shaped box. The pouch does not leak activated carbon but allows air to flow. The pouch can be, for example, made of cloth or non-woven fabric. As the disk-shaped box, for example, a metal net, a punching metal, or the like that can hold a pouch and allow air to flow can be adopted. As shown in FIG. 2, a plurality of disk-shaped boxes may be arranged along the axial direction of the tube body 10. The reason why the first sound absorbing material 22 has a circular outer shape is that the pipe body 10 of the present embodiment has a cylindrical shape, but the outer shape of the first sound absorbing material 22 is appropriately set according to the inner surface shape of the pipe body 10. can do.

The second sound absorbing material 24 is provided around the first sound absorbing material 22. The second sound absorbing material 24 is an annular member that supports the first sound absorbing material 22. The inner diameter of the second sound absorbing material 24 is equal to or larger than the inner diameter of the pipe body 10. This is because the air permeability of the tube body 10 is not impaired. The outer diameter of the second sound absorbing material 24 may be larger than the outer diameter of the pipe body 10. As the second sound absorbing material 24, for example, a material capable of attenuating high-frequency sound more than the first sound absorbing material 22 can be adopted. As the material of the second sound absorbing material 24, for example, glass wool, rock wool or the like can be adopted. When the sound absorbing member 20 does not include the second sound absorbing material 24, the first sound absorbing material 22 may be directly fixed to the inner surface of the pipe body 10.

The low frequency sound reduction structure of the tube 10 reduces the acoustic particle velocity of c / 2L (Hz) to c / 2D (Hz) (where c: sound velocity (m / s), L: tube 10 Length (m), D: Cross-sectional width of the tube determined by the cross-sectional shape of the tube 10).

3. 3. Low-frequency sound reduction structure according to the modified example The low-frequency sound reduced structure of the tube 100 according to the modified example will be described with reference to FIG. FIG. 3 is a schematic view of the tubular body 100 according to the modified example. FIG. 3A is a vertical cross-sectional view of the tubular body 100, and FIG. 3B is a front view of the tubular body 100 as viewed from the direction of the arrow in FIG. 3A.

As shown in FIG. 3, the tubular body 100 has a first end portion 111 and a second end portion 112 as both end portions in the longitudinal direction that open to the outside. The tubular body 100 may be, for example, a cylinder having a substantially cylindrical shape but having a substantially rectangular cross section. The pipe body 100 is a continuation of a diameter-expanded portion 113 that gradually expands in diameter from the first end portion 111 to the second end portion 112, a horizontal portion 114 of the cylinder, and a diameter-reduced portion 115 that gradually reduces in diameter. And have.

The sound absorbing member 200 is provided inside the diameter-expanded portion 113 to the diameter-reduced portion 115. The sound absorbing member 200 includes a substantially cylindrical third sound absorbing material 210a extending along the axial direction of the tubular body 100, and a substantially cylindrical fourth sound absorbing material 210b concentrically arranged around the third sound absorbing material 210a. including. The sound absorbing member 200 can be set according to the inner surface shape of the pipe body 100.

As shown in FIG. 3A, there is a gap between the third sound absorbing material 210a and the fourth sound absorbing material 210b and between the fourth sound absorbing material 210b and the inner surface of the pipe body 100, and air is introduced. It is allowed to flow between the 1st end 11 and the 2nd end 12. The third sound absorbing material 210a is formed with both ends in the axial direction having a conical shape and tapering. Both ends of the fourth sound absorbing material 210b are tapered in the axial direction, and the inner diameter of the tip thereof is the same as or smaller than the maximum outer diameter of the third sound absorbing material 210a.

As shown in FIG. 3B, when the sound absorbing member 200 is viewed from the direction of the arrow in (a), there is no gap between the third sound absorbing material 210a and the fourth sound absorbing material 210b, and the fourth sound absorbing material 210b The second end 12 side cannot be seen from the opening at the tip of the. Therefore, the sound wave incident from the first end 11 side along the axial direction of the pipe body 100 always collides with the third sound absorbing material 210a or the fourth sound absorbing material 210b, and the third sound absorbing material 210a and the fourth sound absorbing material 210a and the fourth sound absorbing material 210a. The sound absorbing material 210b can efficiently reduce low frequency sound.

As the material of the third sound absorbing material 210a and the fourth sound absorbing material 210b, the material of the first sound absorbing material 22 can be adopted. Since the third sound absorbing material 210a and the fourth sound absorbing material 210b are spaced apart from each other to ensure breathability, a material having low breathability such as glass wool or rock wool can be adopted.

4. Double-skin sound-absorbing structure The sound-absorbing structure of the double-skin 40 having a sound-absorbing structure will be described with reference to FIG. FIG. 4 is a perspective view schematically showing the double skin 40. In FIG. 4, the structure of the building such as the floor is omitted, and only the double skin 40 is shown in a simplified manner. Further, in FIG. 4, a part of the lower portion of the double skin 40 is cut out to show the sound absorbing member 50.

In the double skin 40, the first glass 46 that functions as an outer wall and the second glass 47 on the living room side are arranged so as to face each other. The double skin 40 has an air layer between the first glass 46 and the second glass 47. The first glass 46 and the second glass 47 are connected by a first side wall 48 and a second side wall 49 at their lateral ends. The first end 42 at the lower end of the double skin 40 and the second end 44 at the upper end are opened to the outside. Therefore, the double skin 40 can be said to be a pipe body extending in the vertical direction of the building.

In the double skin 40, noise from the outside is taken into the inside of the double skin 40 from the first end portion 42 and the second end portion 44. Therefore, the acoustic particle velocity described in the tube body 10 is maximized in the first end portion 42 and the second end portion 44 in the double skin 40 as well.

The double skin 40 includes a sound absorbing member 50 at the first end portion 42. The sound absorbing member 50 is arranged so as to close the entire opening of the first end portion 42. The sound absorbing member 50 can adopt the same structure and material as the sound absorbing member 20 used for the pipe body 10. For example, the sound absorbing member 50 packs a large number of bags containing activated carbon in a metal net box that covers the entire opening of the first end portion 42. The sound absorbing member 50 reduces low frequency sound while ensuring air permeability from the first end portion 42. The low frequency sound reduction structure of the tube 100 reduces the acoustic particle velocity of c / 2L (Hz) to c / 2D (Hz) (where c: sound velocity (m / s), L: tube. The sound particle velocity of the length (m) of 100, D: the cross-sectional width of the tube body determined by the cross-sectional shape of the tube body 100) is reduced.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the present invention includes a configuration that is substantially the same as the configuration described in the embodiment (for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect). The present invention also includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the present invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

10 ... tube, 11 ... first end, 12 ... second end, 20 ... sound absorbing member, 22 ... first sound absorbing material, 24 ... second sound absorbing material, 100 ... tube, 111 ... first end, 112 ... 2nd end, 113 ... Enlarged diameter, 114 ... Horizontal, 115 ... Reduced diameter, 200 ... Sound absorbing member, 210a ... 3rd sound absorbing material, 210b ... 4th sound absorbing material, 40 ... Double skin, 42 ... 1st end, 44 ... 2nd end, 46 ... 1st glass, 47 ... 2nd glass, 48 ... 1st side wall, 49 ... 2nd side wall, 50 ... Sound absorbing member

Claims (2)

It is a low-frequency sound reduction structure of a tube with both ends open in the longitudinal direction.
It has a sound absorbing member at one end of the pipe body, and has a sound absorbing member.
The sound absorbing member allows the passage of gas at the end and
The low-frequency sound reduction structure of the tube is a low-frequency sound reduction structure of the tube, characterized in that the acoustic particle velocity of c / 2L (Hz) to c / 2D (Hz) is reduced.
(Here, c: sound velocity (m / s), L: pipe length (m), D: pipe cross-sectional width determined by the cross-sectional shape of the pipe) In claim 1,
The sound absorbing member has a low frequency sound reducing structure of a pipe body, characterized by containing activated carbon.

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