JP7411084B2 - Silencer - Google Patents

Description

The present invention relates to a silencer.

In order to muffle the noise that passes through a ventilating through hole provided in a wall that separates indoors and outdoors, a sound absorbing material made of urethane, polyethylene, or the like is sometimes installed inside the through hole. For example, in the silencer described in Patent Document 1, a cylindrical high-frequency sound-absorbing member is placed in a ventilation hole corresponding to a through-hole, so that sound-absorbing performance is exhibited in a high-frequency sound range of around 2 kHz.

However, in order to achieve a high absorption rate when using a sound absorbing material, it is necessary to increase the volume of the sound absorbing material. On the other hand, in the through-hole for ventilation, it is necessary to ensure ventilation, and there is a limit to the size of the sound-absorbing material installed inside the through-hole. In other words, when a sound absorbing material is disposed inside the through hole as in Patent Document 1, it becomes difficult to achieve both high air permeability and good soundproofing performance.

Regarding noise passing through the through-holes in the wall, resonance within the through-holes becomes a problem. If the frequency of this resonance sound is 800 Hz or less, the amount of sound-absorbing material will increase significantly if the sound-absorbing material is used for soundproofing. Therefore, even if air permeability is sacrificed, it is difficult to exhibit sufficient soundproofing performance against resonance sounds within the through hole. In order to muffle the resonance sound inside the through hole, a resonance muffler that muffles sound at a specific frequency is sometimes used.

Conventional resonance-type mufflers selectively muffle sounds in a single frequency band, but when the length and shape of the through-hole changes, the resonance frequency within the through-hole also changes. Therefore, there was a problem in that the muffler's versatility was reduced.
In addition, resonance inside the through hole occurs at multiple frequencies, but as mentioned above, conventional resonance-type mufflers mute sound in a single frequency band, and because that frequency band is narrow, resonance at other frequencies occurs. There was a problem in that the sound could not be effectively muffled.

An example of a muffling device that solves the above problems is the device described in Patent Document 2. The muffling device described in Patent Document 2 is installed on a tubular member fitted into a through hole in a wall, and muffles sound passing through the tubular member. The silencer has a plurality of silencers arranged on one end surface side of the wall, and each silencer includes a cavity and an opening that communicates the cavity with the outside. At least one of the openings of the muffler is connected to the sound field space of the first resonance of the tubular member. Further, a sound absorbing material is arranged in at least a part of the cavity of the muffler or in a position covering at least a part of the opening of the muffler. Further, the depth Ld of the cavity in the direction of propagation of the sound waves inside the muffler is larger than the width of the opening in the axial direction of the tubular member. Further, if λ is the wavelength of the sound wave at the resonant frequency of the first resonance generated in the tubular member in the silencing system including the silencing device, then the depth Ld of the cavity is 0.011×λ<Ld<0.25×λ is met.

Patent No. 3664675 JP2019-56816A

According to the muffler described in Patent Document 2, it is possible to muffle a plurality of resonance sounds, and there is no need for a design tailored to the installation environment, resulting in high versatility. However, the noise reduction device described in Patent Document 2 cannot sufficiently silence resonance sounds at specific frequencies (for example, around 500 Hz and around 1000 Hz) among resonance sounds at frequencies higher than the frequency of the first resonance of the tubular member. There may be no.

The present invention has been made in view of the above-mentioned circumstances. Specifically, the present invention solves the problems of the above-mentioned prior art, ensures high air permeability, mutes multiple resonance sounds, and improves walls. It is an object of the present invention to provide a muffling device that can satisfactorily muffle sound passing through a ventilation hole including a through hole.

As a result of intensive studies to solve the above problems, the present inventors discovered that the above object could be achieved by the following configuration, and completed the present invention.

[1] A sound muffling device in which a muffler is placed on one side of a wall to muffle sound passing through a ventilation hole including a through hole in the wall, and the muffler has a plurality of cavities and a muffler in each cavity. It has an opening that communicates between the ventilation hole and the cavity, and a sound absorbing material placed in each cavity, and each cavity resonates at a different frequency to muffle the sound, has a portion located outside the vent in the cross direction that intersects the extending direction of the vent, and the openings of the respective cavities are located at different positions in the extending direction, and A silencer connected to a resonant sound field space, in which the resonant frequency in a cavity having an opening closest to the wall is higher than the resonant frequency in a cavity having an opening farthest from the wall.
[2] The silencer according to [1], wherein the silencer has a partition wall that partitions the cavities from each other.
[3] The plurality of cavities include a first cavity and a second cavity that are adjacent to each other in the extending direction, and the opening of the second cavity is farther from the wall than the opening of the first cavity. , the silencer according to [1] or [2], wherein the second cavity has a bent shape, and a portion of the second cavity is located in the range where the first cavity exists in the extending direction.
[4] The silencer further includes a ventilation portion that is continuous with the internal space of the ventilation sleeve inserted into the through hole in the extending direction, and the silencer is disposed at a position surrounding the ventilation portion in the cross direction. [1] - The silencer according to any one of [3].
[5] The sound deadening device according to any one of [1] to [4], wherein the sound deadening device is disposed between the wall and the decorative board that is spaced apart from the wall in the extending direction.
[6] The silencer according to any one of [1] to [5], wherein the number of the plurality of hollow parts is two.
[7] The silencer according to any one of [1] to [6], wherein the volume of the cavity having the opening furthest from the wall is larger than the volume of the cavity having the opening closest to the wall.
[8] The partition wall has a first partition wall piece and a second partition wall piece that extends from the first partition wall piece toward the wall along the extension direction, and the first partition wall piece extends in the cross direction. The silencer according to [2], which has a protruding portion that protrudes outward from the second partition wall piece.
[9] The muffler does not resonate with the sound of the first resonance frequency occurring in the vent, and in the cavity having the opening farthest from the wall, the resonance frequency is higher than the first resonance frequency. The silencer according to any one of [1] to [8], which resonates at.
[10] Among the resonances inside the vent, the frequency of the second resonance, which is the next highest resonance frequency after the first resonance, was set as f2, and the resonance frequency in the cavity having the opening farthest from the wall was set as fs2. In the case, the resonance frequency fs2 satisfies 0.8×f2<fs2<1.2×f2, the silencer according to [9].
[11] The silencer according to [10], wherein the resonance frequency fs2 satisfies 0.9×f2<fs2<1.1×f2.

According to the present invention, multiple resonance sounds are muffled while ensuring high air permeability, and in particular, resonance sounds with a frequency higher than the frequency of the first resonance generated in the ventilation hole (specifically, the second resonance sound, which will be described later), are resonance and third resonance) can be effectively silenced. As a result, the sound damping device of the present invention can satisfactorily muffle the sound passing through the ventilation holes including the through holes in the wall.

1 is a schematic cross-sectional view of a sound deadening system including a sound deadening device according to an embodiment of the present invention. FIG. 1 is a front view of a silencer according to an embodiment of the present invention. FIG. 2 is a rear view of a silencer according to an embodiment of the present invention. It is a typical sectional view of the sound deadening system including the sound deadening device concerning the first modification of the present invention. It is a typical sectional view of the silencing system including the silencing device concerning the second modification of the present invention. It is a typical sectional view of a sound deadening system including a sound deadening device of a reference example. It is a figure which shows the transmission loss when using the muffler of a reference example. It is a graph which shows the dependence on the diameter size of a silencer about the silencing effect by the silencer of a reference example. FIG. 2 is a diagram conceptually representing the particle velocity (moving speed of gas molecules) during resonance in a silencing system including a silencing device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of a silencing device used in the simulation. FIG. 3 is a front view of the silencer used in the simulation. FIG. 3 is a rear view of the silencer used in the simulation. FIG. 3 is a diagram showing a first calculation model for calculating the resonant frequency of the silencer. It is a figure which shows the second calculation model for calculating the resonant frequency of a silencer. It is a figure which shows the calculation result of the resonance frequency in each muffler. FIG. 3 is a schematic cross-sectional view of the silencing system used in the simulation. It is a figure which shows the transmission loss calculated by changing the diameter size of the silencer in simulation. It is a figure which shows the difference from grade T2 calculated by changing the diameter size of a silencer in simulation. It is a graph showing the dependence of the silencing effect of the silencing device of the example on the diameter size of the silencing device. It is a figure which shows the calculation result of the resonance frequency in each cavity part of the muffler which the muffler of a reference example has. It is a figure which shows the difference from grade T2 calculated by changing the diameter size of a silencer about the silencer of a reference example. FIG. 2 is a conceptual diagram showing a measurement environment for normalized transmission loss. It is a figure which shows the transmission loss actually measured by changing the diameter size of the silencer in an experiment. It is a figure which shows the difference from grade T2 calculated based on the transmission loss actually measured by changing the diameter size of the silencer in an experiment.

Hereinafter, embodiments of the soundproofing device of the present invention will be specifically described with reference to the accompanying drawings. Note that, although each part of the soundproofing device described below will be explained based on a typical embodiment of the present invention, the present invention is not limited to such an embodiment.

Furthermore, in this specification, a numerical range expressed using "-" means a range that includes the numerical values written before and after "-" as lower and upper limits.
Furthermore, in this specification, "orthogonal" or "parallel" includes the generally acceptable error range in the technical field of the present invention. For example, "orthogonal" or "parallel" includes a state where the angles are deviated within a range of less than ±10° from strict orthogonality or parallelism. Note that the error with respect to strict orthogonality or parallelism is preferably 5° or less, more preferably 3° or less.
In addition, in this specification, "same", "same", "equal", or "match" shall include the generally accepted error range in the technical field of the present invention.
In addition, in this specification, "all,""all," or "entire surface" includes not only 100% but also the generally accepted error range in the technical field of the present invention, such as 99% or more. , 95% or more, or 90% or more.

The muffler of the present invention includes a muffler placed on one side of a wall, and muffles sound passing through a vent including a through hole in the wall. The muffler does not resonate with the sound at the first resonance frequency that occurs inside the vent, but resonates with the sound at the second and third resonance frequencies that are higher than the first resonance frequency that occur inside the vent. It resonates and mutes the sound.
The silencing device of the present invention is used, for example, in the silencing system shown in FIG. A silencer and a silencer system according to the embodiment shown in FIG. 1 (hereinafter referred to as the present embodiment) will be described below.

[Sound deadening system]
The muffler according to this embodiment (hereinafter referred to as muffler 10 ) constitutes a muffler system 1 . The structure of the silencer 10 will be described with reference to the cross-sectional view shown in FIG. 1 (strictly speaking, the cross-section along the central axis direction and the vertical direction of the through hole 2a).

In the silencing system 1, as shown in FIG. 1, a ventilation sleeve 4 is inserted into a through hole 2a of a wall 2. The wall 2 is made of, for example, a concrete wall, and constitutes a building wall that separates an indoor space from an outdoor space together with a gypsum board and a heat insulating material (not shown), a decorative board 8 shown in FIG. 1, and the like. A ventilation hole 6 including a through hole 2a of the wall 2 is formed in the building wall. The ventilation hole 6 extends straight along the thickness direction of the wall 2. That is, the extending direction of the ventilation hole 6 is a direction along the thickness direction of the wall 2. Hereinafter, the extending direction of the ventilation holes 6 will be simply referred to as the "extending direction."

Sound (noise) emitted from an outdoor sound source passes through the ventilation hole 6. In the following, for convenience of explanation, in the extension direction, the outdoor side, that is, the side where the sound source is located, will also be referred to as the "front side," and the indoor side will also be referred to as the "rear side."

The ventilation sleeve 4 is a straight tubular member constituting a ventilation opening or an air conditioning duct, and is inserted into the through hole 2a and fitted into the wall 2. A cover member 12 made of a known louver is attached to the front end of the ventilation sleeve 4, that is, the open end on the outdoor side.

A decorative board 8 is arranged on the rear side of the wall 2 at a predetermined distance from the wall 2. The decorative board 8 is provided with a mounting hole 8a. The attachment hole 8a is, for example, a circular hole, and the center of the attachment hole 8a is located on an extension of the central axis of the ventilation sleeve 4. An air volume adjustment member 14 made of a known resistor is attached to the attachment hole 8a.

A silencer 10 is disposed on the rear side (one side) of the wall 2, sandwiched between the wall 2 and the decorative board 8. The muffling device 10 muffles sounds transmitted indoors from outside through the ventilation holes 6, and has an appearance shown in FIGS. 2 and 3. 2 shows the front side of the silencer 10, and FIG. 3 shows the rear side of the silencer 10. Further, the silencer 10 includes an insertion portion 22 and a main body portion 24, as shown in FIG.

The insertion portion 22 has a cylindrical shape with both ends open, and protrudes from the front end surface of the main body portion 24 . The outer diameter of the insertion portion 22 is approximately the same as the inner diameter of the ventilation sleeve 4. As shown in FIG. 1, the insertion part 22 is inserted into the rear end of the ventilation sleeve 4, that is, the opening end on the indoor side, with the central axis of the insertion part 22 and the central axis of the ventilation sleeve 4 aligned. inserted. Thereby, the muffler 10 is attached to the rear end of the ventilation sleeve 4 as shown in FIG.

The main body part 24 constitutes the main body part of the silencer 10, and has a substantially rectangular parallelepiped-shaped casing 24a.As shown in FIG. 1, the length of the casing 24a in the extending direction (that is, the thickness of the main body part 24) is , corresponds to the distance between the wall 2 and the decorative board 8. In this manner, in this embodiment, the muffling device 10, more specifically, the main body portion 24, can be arranged in a space between the wall 2 and the decorative board 8 in a well-fitting manner. However, the present invention is not limited to this, and the thickness of the main body portion 24 may be somewhat smaller than the distance between the wall 2 and the decorative board 8.

Inside the casing 24a, as shown in FIG. 1, a ventilation section 26 and a muffler 28 are provided. The ventilation part 26 is a cylindrical hole extending from the front end to the rear end of the main body part 24, and is continuous with the internal space of the insertion part 22 in the extending direction, and is located on an extension of the central axis of the insertion part 22. The central axis of the ventilation section 26 is located at . The ventilation hole 6 is formed by aligning the through hole 2a of the wall 2 (strictly speaking, the internal space of the ventilation sleeve 4), the ventilation portion 26, and the mounting hole 8a of the decorative board 8 in a straight line. That is, the ventilation hole 6 includes the through hole 2a of the wall 2.

In this embodiment, as shown in FIG. 1, the diameter of the ventilation part 26 changes at a midway position, and the diameter of the part near the air volume adjustment member 14 (register) is larger than the diameter of the other part. It's getting bigger. Accordingly, by enlarging the mounting hole 8a, a larger air volume adjusting member 14 (register) can be installed. However, the ventilation portion 26 is not limited to the above shape, and may have a straight shape in which the inner diameter is constant from the front end to the rear end of the ventilation portion 26, as shown in FIG.

The muffler 28 is arranged in an annular shape at a position surrounding the ventilation portion 26 in the radial direction of the ventilation portion 26 . Note that the radial direction of the ventilation portion 26 corresponds to a crossing direction that intersects the extension direction, and will be hereinafter referred to as a "radial direction" for convenience.
As shown in FIG. 1, the silencer 28 has a plurality of cavities 31 and 32 inside, and openings 31a and 32a provided in the respective cavities 31 and 32, and openings 31a and 32a provided in the respective cavities 31 and 32. It further includes a sound absorbing material 34 disposed therein, and a partition wall 36 that partitions the cavities 31 and 32 from each other.

The silencer 28 of this embodiment has two cavities, that is, a first cavity 31 and a second cavity 32, as shown in FIG. 1, but the number of cavities may be three or more. good. The first cavity part 31 and the second cavity part 32 are adjacent to each other in the extension direction, and extend in the extension direction and the radial direction (cross direction), respectively. The shape and volume (size) of each of the first cavity part 31 and the second cavity part 32 are defined by the partition wall 36.

The partition wall 36 has a horizontal T-shape, and as shown in FIG. It has a second partition wall piece 38 extending toward the wall 2 along the extending direction from a midway position of the piece 37.

The first partition wall piece 37 is a portion in which a circular hole is formed in the center portion to form the ventilation portion 26. The second partition wall piece 38 is a cylindrical portion, and extends to a surface located at the front end of the inner wall surface of the casing 24a. Further, as shown in FIG. 1, the first partition wall piece 37 is provided with a protruding portion 37a that protrudes outward from the second partition wall piece 38 in the radial direction. However, the partition wall 36 may have a structure in which the protruding portion 37a is not provided, that is, a structure in which the partition wall 36 is bent into an L-shape as shown in FIG. 5.

The first cavity 31 is an annular space surrounded by the front end portion of the casing 24a and the partition wall 36 in the muffler 28, and located on the front side of the partition wall 36 (ie, on the wall 2 side). The first cavity 31 includes a portion located outside the ventilation hole 6 in the radial direction (crossing direction), and in this embodiment, as shown in FIG. substantially the entirety thereof is located radially outward from the ventilation hole 6. However, the present invention is not limited to this, and the first cavity portion 31 may be partially located inside the ventilation hole 6 in the radial direction.

An annular wall 39 extending toward the front from the first partition wall piece 37 is disposed at the radially inner end of the first cavity 31, and between the annular wall 39 and the front end of the casing 24a. A gap is provided. This gap forms the opening of the first cavity 31 (hereinafter referred to as the first opening 31a). The first opening 31a is a slit-shaped opening that communicates the ventilation hole 6 with the first cavity 31, and is located at a position in the first cavity 31 facing the ventilation hole 6 (strictly speaking, the ventilation section 26). It is set in. The first openings 31a may be provided continuously over the entire circumference in the circumferential direction of the first cavity portion 31, or may be provided intermittently at a constant pitch.

In addition, the structure may be such that the annular wall 39 is not provided, and in that case, the gap between the first partition wall piece 37 and the front end of the casing 24a will form the first opening 31a.

The second cavity portion 32 is a space surrounded by the front end portion, rear end portion, and outer peripheral portion of the casing 24a, and the partition wall 36, and at least a portion thereof is located on the rear side of the partition wall 36. The second cavity 32 includes a portion located outside the ventilation hole 6 in the radial direction (cross direction), and in this embodiment, as shown in FIG. substantially the entirety thereof is located radially outward from the ventilation hole 6. However, the present invention is not limited to this, and the second cavity portion 32 may be located partially inside the ventilation hole 6 in the radial direction.
Further, in this embodiment, the volume of the second cavity 32 is larger than the volume of the first cavity 31. Here, the volume refers to the size of the space located inside the opening in each cavity (in other words, the volume of the closed space formed when the opening is closed).

When viewed in cross section, the second cavity portion 32 has a substantially U-shaped bend. To explain in detail with reference to FIG. 1, the second cavity 32 includes a rear part 32b located between the first partition wall piece 37 and the rear end part of the casing 24a, a rear part 32b located between the first partition wall piece 37 and the rear end part of the casing 24a, and a rear part 32b located between the first partition wall piece 37 and the rear end part of the casing 24a and the first partition wall piece 37, and an intermediate portion 32d located between the rear portion 32b and the front portion 32c in the extending direction.

As shown in FIG. 1, the intermediate portion 32d connects the rear portion 32b and the front portion 32c at a position adjacent to the protruding portion 37a of the first partition wall piece 37 in the radial direction. The front portion 32c is arranged at a position adjacent to the first cavity portion 31 with the second partition wall piece 38 in between. In other words, the front portion 32c, which is a part of the second cavity 32, is located in the range where the first cavity 31 exists in the extending direction.

An annular wall 40 extending from the rear end portion of the casing 24a toward the front side is disposed at the radially inner end position of the rear portion 32b of the second cavity portion 32, and the annular wall 40 and the first partition wall piece 37 A gap is provided between the two. This gap forms the opening of the second cavity 32 (hereinafter referred to as the second opening 32a). The second opening 32a is a slit-shaped opening that communicates the ventilation hole 6 with the second cavity 32, and is located at a position in the second cavity 32 facing the ventilation hole 6 (strictly speaking, the ventilation section 26). It is set in. The second openings 32a may be provided continuously over the entire circumference in the circumferential direction of the second cavity portion 32, or may be provided intermittently at a constant pitch.
In addition, the structure may be such that the annular wall 40 is not provided, and in that case, the gap between the first partition wall piece 37 and the rear end of the casing 24a forms the second opening 32a.

Further, the second cavity portion 32 is not limited to the U-shaped bent (strictly speaking, folded) shape as shown in FIG. 1 . For example, if the partition wall 36 is bent in an L-shape as shown in FIG. configuration). However, when the second cavity part 32 is bent in a U-shape, the sound transmission path in the second cavity part 32 becomes longer and better than when it is bent in an L-shape. This is more preferable because it provides soundproofing performance.

Explaining the first opening 31a and the second opening 32a, both openings are located at different positions in the extending direction, as shown in FIG. The first opening 31a is located further to the front, and the second opening 32a is located further to the rear, and is further away from the wall 2 than the first opening 31a. In other words, the first cavity 31 corresponds to the cavity having the opening closest to the wall 2, and the second cavity 32 corresponds to the cavity having the opening farthest from the wall 2.
Note that the first opening 31a and the second opening 32a may be located at different positions in the radial direction as shown in FIG. 1, or may be located at the same position in the radial direction (crossing direction) as shown in FIG. Good too.

Further, each of the first opening 31a and the second opening 32a is connected to a resonant sound field space in the ventilation hole 6. The resonant sound field space in the ventilation hole 6 is a space in which resonance of sound passing through the ventilation hole 6 occurs in the silencing system 1, and includes the internal space of the ventilation sleeve 4, the ventilation portion 26 of the silencing device 10, and the open end correction. It is a space that includes the space within the distance. When an opening is connected to a resonant sound field space, it means that the opening exists within the above-mentioned sound field space, and in order to connect the sound field space and the opening, there is a A case in which a sound absorbing material or a breathable member is interposed may also be included.

The sound absorbing material 34 mutes sound by converting sound energy into thermal energy, and its type is not particularly limited, and any known sound absorbing material can be used as appropriate. For example, foamed materials such as urethane foam, flexible urethane foam, wood, sintered ceramic particles, phenol foam, and materials containing minute air; glass wool, rock wool, microfibers (such as 3M Thinsulate), floor mats. , carpets, melt-blown nonwoven fabrics, metal nonwoven fabrics, polyester nonwoven fabrics, metal wool, felt, insulation boards, and fiber and nonwoven materials such as glass nonwoven fabrics; wood wool cement boards; nanofiber materials such as silica nanofibers; gypsum boards; others A variety of known sound absorbing materials are available.

The thickness of the sound absorbing material 34 is not particularly limited as long as the sound absorbing material 34 can be placed within the cavities 31 and 32 or near the openings 31a and 32a. In addition, from the viewpoint of sound absorption performance, etc., the flow resistance of the sound absorbing material 34 is preferably 100 Pa·s/m ² to 100000 Pa·s/m ² , more preferably 500 Pa·s/m ² to 40000 Pa·s/m ² , Particularly preferred is 1000 Pa·s/m ² to 10000 Pa·s/m ² .

Further, when the sound absorbing material 34 is disposed within the cavities 31 and 32, it is preferable that the shape of the sound absorbing material 34 is molded to match the shape of the cavities 31 and 32. This makes it easy to uniformly fill the sound-absorbing material 34 into the cavities 31 and 32, reducing costs and simplifying maintenance. Note that, as shown in FIG. 1, a part of the sound absorbing material 34 disposed within the cavity may protrude from the cavity through an opening (second opening 32a in FIG. 1). In this case, although the air permeability is slightly reduced, it is sufficient that the air permeability is higher than that of the air volume adjusting member 14 such as a register installed on the indoor side. Based on this point, it is preferable to design the muffler 28 in consideration of the "equivalent gap area" which indicates the ventilation performance of a general ventilation port member. Specifically, when the equivalent gap area of the air volume adjustment member 14 is aA _R (cm ² ) and the equivalent gap area of the silencer 28 is aA _S (cm ² ), 1.0×aA _R <aA _S It is preferable that 1.5×aA _R <aA _S , more preferably 1.5×aA R <aA S, and particularly preferably 2.0×aA _R <aA _S.

The muffler 28 configured as described above resonates at different frequencies in the respective cavities 31 and 32 to muffle the sound. To explain in more detail, the muffler 28 does not resonate with the sound of the first resonance frequency generated inside the vent 6. Here, the first resonance is a fundamental mode resonance among the resonances occurring within the vent hole 6. The resonance occurring in the vent hole 6 is the resonance in the entire system of the silencing system 1. Moreover, the first resonance corresponds to the first resonance occurring within the ventilation sleeve 4.

On the other hand, the muffler 28 resonates in each of the first cavity 31 and the second cavity 32 at a resonance frequency higher than the first resonance frequency. To explain in more detail, a second resonance occurs in the second cavity portion 32, and a third resonance occurs in the first cavity portion 31. The second resonance is a resonance that has the next highest resonance frequency after the first resonance among the resonances in the vent hole 6, and the third resonance is a resonance that is higher-order than the second resonance and is next to the second resonance. It is a resonance with a high resonant frequency.

In the present embodiment, the resonant frequency fs1 at the first cavity 31 having the opening closest to the wall 2 (the first opening 31a) is different from that at the opening farthest from the wall 2 (the second opening 32a). is higher than the resonant frequency fs2 in the second cavity portion 32 having the following. Thereby, it is possible to muffle a plurality of resonance sounds with a highly versatile configuration while ensuring high air permeability, and it becomes possible to effectively muffle the noise passing through the ventilation holes 6.

To explain in more detail, when using a conventional resonant silencer to muffle sound passing through a through hole in a wall, the resonance frequency generated in the ventilation sleeve inserted into the through hole (for example, the Since a length of 1/4 of the wavelength corresponding to one resonance frequency is required, the size of the muffler tends to increase. Therefore, there was a problem in that it was difficult to achieve both high air permeability and soundproofing performance.
Furthermore, since conventional resonance-type mufflers selectively muffle sounds at specific frequencies (frequency bands), they require a design that matches the resonant frequency of the ventilation sleeve, resulting in a problem of low versatility. Additionally, resonance in the vent sleeve occurs at multiple frequencies, and as previously discussed, conventional resonant silencers selectively silence sounds at specific frequencies. For this reason, there is a problem in that the resonance sound to be muffled is only of a single frequency, and furthermore, the frequency band muffled by the resonance type muffler is narrow, and resonance sounds of other frequencies are not muffled.

The present inventors have found that the above problem can be solved by a silencer having a silencer 120 shown in FIG. 6 (hereinafter referred to as a silencer 110 of a reference example). In the silencer 110 of the reference example, as shown in FIG. 6, a silencer 120 is arranged around the ventilation section 112 that communicates with the inside of the ventilation sleeve 4. Two cavities 131 and 132 having the same length (as shown) are provided. The two cavities 131 and 132 are partitioned back and forth by a partition wall 136 that extends straight in the radial direction. Each of the cavities 131 and 132 is provided with an opening 13a and 132a connected to the resonant sound field space in the ventilation hole 6, and a sound absorbing material 134 is disposed within the cavity 131 and 132. Further, the silencer 120 resonates at different frequencies in the plurality of cavities 131 and 132 to mute the sound.

With the noise muffling device 110 of the reference example configured as described above, it is possible to muffle sounds of multiple frequencies even if the size is smaller than 1/4 of the wavelength corresponding to the resonant frequency of the ventilation sleeve 4. High soundproofing performance can be achieved. Furthermore, the muffler 120 is not disposed within the ventilation sleeve 4 but is disposed outside the ventilation sleeve 4 in the radial direction, so that sufficient ventilation is ensured. Furthermore, with the noise damping device 110 of the reference example, a good sound damping effect can be obtained even when the length of the ventilation sleeve 4 changes, so there is no need to design according to the length of the ventilation sleeve 4, and versatility is achieved. improves.

However, as shown in FIG. 7, in the noise damping device 110 of the reference example, although good soundproofing performance is obtained over a wide range, the soundproofing performance tends to deteriorate at a plurality of specific frequencies. To be more specific, at each of the frequencies of the second resonance and the third resonance occurring inside the vent 6 (around 500 Hz and around 1000 Hz in FIG. A 4706-4702), which indicates the soundproofing performance (sound insulation performance) of residential sashes, is lower than class T2 soundproofing sashes. FIG. 7 is a graph showing the soundproofing performance of the noise damping device 110 of the reference example, in which the horizontal axis represents frequency (Hz) and the vertical axis represents transmission loss (dB).

On the other hand, the silencing effect of the silencing device 110 of the reference example changes depending on the diameter size L of the cavities 131 and 132 in the silencing device 120. Here, when the diameter size L is increased, as shown in FIG. 8, the transmission loss near 500 Hz increases, while the transmission loss near 1000 Hz decreases, indicating a trade-off relationship. FIG. 8 is a graph showing the dependence of the silencing effect by the silencing device 110 of the reference example on the diameter size L, where the horizontal axis represents the radial size L (mm), and the vertical axis represents the transmission loss due to the silencing device 110. Each represents the difference (dB) from the transmission loss due to the soundproof sash of class T2.

On the other hand, in the silencer 10 of this embodiment, the resonance frequency fs1 in the first cavity part 31 having the opening closest to the wall 2 is different from the resonance frequency fs1 in the second cavity part 31 having the opening farthest from the wall 2. higher than the resonant frequency fs2 at . This improves the silencing effect of the silencing device 10 at each of the second resonance and third resonance frequencies.

The mechanism by which the above effect occurs will be explained with reference to a conceptual diagram of particle velocity (moving velocity of gas molecules) during resonance shown in FIG. 9. As described above, the resonance sound field space in the ventilation hole 6 is a space including the internal space of the ventilation sleeve 4, the ventilation portion 26 of the muffling device 10, and the space within the open end correction distance. As is well known, in a resonant space where the air column resonates, the position of the antinode of the standing wave protrudes outside the ventilation sleeve 4 by a distance corresponding to the open end correction. In addition, when the ventilation sleeve 4 is a cylindrical pipe, the open end correction distance is approximately given by 1.2×pipe diameter.

At the free end of the air column resonance, the particle velocity becomes the antinode of the standing wave, and the particle velocity increases. Here, as shown in FIG. 9, the smaller the frequency (that is, the larger the wavelength), the greater the distance by which the position of the antinode protrudes outside the ventilation sleeve 4, that is, the distance for open end correction. Conversely, the larger the frequency (that is, the smaller the wavelength), the smaller the distance that the antinode protrudes outside the ventilation sleeve 4.

Therefore, as shown in FIG. 9, among the resonances occurring within the ventilation hole 6, the waveform antinodes of the second resonance are located further away from the ventilation sleeve 4, and the waveform antinodes of the third resonance are located further away from the ventilation sleeve 4. It is located closer to 4. Taking this into consideration, in this embodiment, the resonance frequency fs1 in the first cavity 31 having the opening closest to the wall 2 is set to a higher frequency, and the resonance frequency fs1 in the first cavity 31 having the opening closest to the wall 2 is set to a higher frequency, and the resonance frequency fs1 in the first cavity 31 having the opening closest to the wall 2 is set to a higher frequency. The resonance frequency fs2 in the cavity 32 was set to a lower frequency. As a result, as shown in FIG. 9, the sound of the second resonance frequency enters the second cavity part 32 where the resonance frequency is lower and is attenuated within the second cavity part 32, and the sound of the third resonance frequency goes into the second cavity part 32 where the resonance frequency is lower. The sound enters the first cavity 31 where the resonance frequency is higher and is attenuated within the first cavity 31. As a result, resonance noise generated within the vent hole 6 can be effectively muffled.

In addition, in order to more effectively muffle the resonance sound generated in the vent hole 6, it is desirable that the resonance frequency in the second cavity portion 32 is near the frequency of the second resonance. For this reason, when the frequency of the second resonance is f2 and the resonance frequency in the second cavity 32 is fs2, it is preferable that the resonance frequency fs2 satisfies the following formula (1), and the following formula ( It is more preferable to satisfy 2).
0.8×f2<fs2<1.2×f2 (1)
0.9×f2<fs2<1.1×f2 (2)

The resonance frequency of each of the first cavity part 31 and the second cavity part 32 depends on the structure and size of each cavity part, and specifically, for example, the width of the opening (length in the extending direction), It is determined depending on the diameter size and volume of the cavity. Generally, as the diameter size and volume increase, the resonance frequency tends to decrease, so in this embodiment, the volume of the second cavity 32 is larger than the volume of the first cavity 31.

Although the configuration of the silencer 10 according to the present embodiment has been described above, the above-mentioned configuration is merely an example and does not limit the present invention. That is, the present invention may be modified or improved from the above embodiments without departing from the spirit thereof. The present invention also includes equivalents thereof.

In the above configuration, the muffler 28 is arranged in the substantially rectangular parallelepiped-shaped casing 24a, and the hollow part (the first hollow part 31 and the second hollow part 32) of the muffler 28 is surrounded by the casing 24a and the partition wall 36. It was decided to be a space. However, the present invention is not limited to this, and a cylindrical frame is arranged between the wall 2 and the decorative board 8, a partition wall 36 is provided on the inner peripheral surface of this frame, and the above frame, wall 2 and decorative board 8 are arranged. The space surrounded by the partition wall 36 and the partition wall 36 may be used as a cavity.

Further, in the above configuration, the silencer 10 is provided with the insertion part 22, and the silencer 10 is attached to the wall 2 by inserting the insertion part 22 into the ventilation sleeve 4. This eliminates the need to change the diameter of the through hole 2a in the wall 2, making it possible to easily install the silencer 10 without performing large-scale construction work on existing ventilation ports, air conditioning ducts, etc. . Moreover, the replacement work of the silencer 10 becomes easy, and it becomes easy to install it as a retrofit when renovating a house. However, the structure is not limited to the above, and the silencer 10 may be provided without the insertion part 22. In that case, the silencer 10 may be attached to the wall 2 with adhesive or adhesive tape.

Further, in the above configuration, the silencer 28 is provided in an annular manner at a position surrounding the ventilation portion 26, and has a continuous structure over the entire circumference in the circumferential direction centered on the central axis of the ventilation portion 26. There is. However, the present invention is not limited to this, and a plurality of silencers 28 may be arranged intermittently at regular intervals in the circumferential direction.

Further, in the above configuration, the ventilation sleeve 4 is fitted into the through hole 2a of the wall 2, but the invention is not limited to this, and the ventilation sleeve does not need to be fitted into the through hole 2a. In this case, the configuration is such that the insertion portion 22 of the silencer 10 is inserted into the through hole 2a. Further, in the above configuration, the decorative board 8 is arranged at a position facing the indoor surface of the wall 2, but the present invention is not limited to this, and a configuration in which the decorative board 8 is not arranged may be used.

Further, in the above configuration, the volume of the second cavity 32 is larger than the volume of the first cavity 31. The present invention is not limited to this, and it is only necessary that the resonant frequency fs1 in the first cavity part 31 is higher than the resonant frequency fs2 in the second cavity part 32, and as long as this is the case, the volume of the first cavity part 31 may be larger than the volume of the second cavity 32.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples. The materials, usage amounts, proportions, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the Examples shown below.

[simulation]
A simulation was conducted regarding the silencing effect etc. of the silencing device of the present invention. For the simulation, we used the acoustic module of COMSOL ver. 5.4, a finite element method calculation software from COMSOL.

(About the silencer)
In the simulation, a silencer 10X having a shape shown in FIGS. 10A to 10C was assumed. The muffling device 10X has an insertion portion 22 and a main body portion 24, and an annular muffler 28 surrounding a ventilation portion 26 is provided in a casing 24a of the main body portion 24. The insertion part 22 had a cylindrical shape with an inner diameter of 100 mm, and the main body part 24 had a substantially rectangular parallelepiped shape with a width w of 255 mm, a thickness t of 90 mm, and a height h of 270 mm. The ventilation portion 26 extends straight and has a larger diameter near the rear end, and has an inner diameter Dr of 150 mm on the rear end side and an inner diameter Df of 100 mm at the other end. Further, in the radial direction, the distance lx from the inner wall surface of the casing 24a of the main body portion 24 to the ventilation portion 26 was set to 85 mm.

The muffler 28 has a first cavity 31 and a second cavity 32, and each of the cavities 31 and 32 has openings 31a and 32a at positions facing the ventilation section 26. Further, the opening width A1 of the first opening 31a of the first cavity 31 was 28 mm, and the opening width A2 of the second opening 32a of the second cavity 32 was 26 mm. Note that, as shown in FIG. 10C, since the diameter of the ventilation portion 26 is expanded near the rear end, the second opening 32a is located radially outward than the first opening 31a.

The first cavity part 31 and the second cavity part 32 are each an annular space continuous over the entire circumference in the circumferential direction centered on the central axis of the ventilation part 26 . The first cavity 31 was located in front of the L-shaped partition wall 36, and had a width W1 of 42 mm. The second cavity portion 32 is curved in an L-shape at the rear side of the partition wall 36, and has a rear portion 32b extending in the radial direction and a front portion 32c extending in the extending direction. The width W2 of the rear portion 32b is 42 mm, and the front portion 32c is located at a position overlapping the first cavity 31 in the radial direction, and its width matches the width W1 of the first cavity 31. Further, the plate thickness of each part of the casing 24a and the partition wall 36 was 2 mm.

A sound absorbing material 34 is placed inside each cavity 31, 32. As the sound absorbing material 34, Micromat manufactured by Soft Prene Kogyo Co., Ltd. was assumed. Note that, as shown in FIGS. 10A and 10C, the sound absorbing material 34 disposed within the second cavity 32 protrudes from the second opening 32a and reaches the same position as the first opening 31a in the radial direction.

In the simulation, the diameter size ly of the first cavity 31 was used as a parameter, and a plurality of sizes were set for the parameter. Note that the maximum value of the diameter size ly is 270 mm, which corresponds to the height h of the silencer 10X, and in this case, while the volume of the first cavity 31 is maximum, the volume of the second cavity 32 is is the minimum since the front portion 32c is eliminated.

(Calculation of resonance frequency of silencer)
In the simulation, first, the resonance frequency of the muffler 28 included in the muffler 10X was calculated using the calculation model shown in FIGS. 11 and 12. In the calculation model of FIG. 11, a muffler (hereinafter referred to as the first muffler 28A) consisting of a first cavity part 31 and a sound absorbing material 34 arranged inside the first cavity part 31 is a straight muffler with a diameter Di of 100 mm. It was attached to the ventilation hole 6. In the calculation model of FIG. 12, a muffler (hereinafter referred to as second muffler 28B) consisting of a second cavity 32 and a sound absorbing material 34 disposed within the second cavity 32 has a diameter Di of 100 mm near the rear end. It was attached to the ventilation hole 6 which expanded to 150 mm. Each ventilation hole 6 is formed in a wall member including a concrete wall and a decorative board.

The first silencer 28A and the second silencer 28B are obtained by dividing the silencer 28 shown in FIG. 10A into each cavity. As shown in FIGS. 11 and 12, the opening on the first muffler 28A side (the first aperture 31a) is closer to the sound wave incidence surface than the opening on the second muffler 28B side (the second aperture 32a). Close to. That is, the resonance frequency of each of the first silencer 28A and the second silencer 28B corresponds to the resonance frequency of each of the first cavity 31 and the second cavity 32 in the silencer 10X of FIGS. 10A to 10C.

Further, the length of the front portion 32c of the second cavity portion 32 in the second silencer 28B changes depending on the diameter size ly of the first silencer 28A, and the larger the diameter size ly, the longer the front portion 32c. becomes shorter.

In addition, in the calculation model of FIG. 11 and the calculation model of FIG. 12, the ventilation hole 6 was each assumed to have infinite length. In each calculation model, while changing the diameter size ly (in the calculation model of FIG. 12, the length of the front part 32c), a plane wave-shaped sound wave is input from one end of the ventilation hole 6 and reaches the other end of the ventilation hole 6. The amplitude per unit volume of the sound waves generated was determined, and the resonance frequency of each silencer 28A, 28B was calculated based on the determined amplitude. Furthermore, in each calculation model, it was assumed that there was no resonance within the vent hole 6, and only resonance of the silencers 28A and 28B was observed. In addition, the acoustic module of COMSOL ver. 5.3, a finite element method calculation software from COMSOL, was used to calculate the resonance frequency.

FIG. 13 shows calculation results of the resonance frequencies of the first muffler 28A and the second muffler 28B. In addition, in FIG. 13, the frequency f2 of the second resonance in the ventilation hole 6 is shown by a broken line.
As shown in FIG. 13, the resonance frequency of each silencer depends on the diameter size ly, and the larger the diameter size ly, the lower the resonance frequency fs1 in the first silencer 28A, and the lower the resonance frequency fs1 in the second silencer 28B. The resonance frequency fs2 becomes higher. Further, when the diameter size ly is 270 mm or more, the resonance frequency fs2 of the second silencer 28B is higher than the resonance frequency fs1 of the first silencer 28A, but for other diameter sizes ly Resonant frequency fs1 is higher than resonant frequency fs2. From this, it can be seen that the diameter size ly has a turning point where the magnitude relationship between the resonance frequency fs1 and the resonance frequency fs2 changes.

When the diameter size ly is larger than the above-mentioned turning point (for example, ly=270 mm), the resonant frequency fs2 becomes higher than the resonant frequency fs1. Therefore, in the simulation and the transmission loss measurement experiment described below, the case where the diameter size ly is 270 mm corresponds to a comparative example that does not meet the requirements of the present invention.
On the other hand, when the diameter size ly is smaller than the turning point, the resonant frequency fs1 becomes higher than the resonant frequency fs2. Therefore, in the simulation and transmission loss measurement experiment, the case where the diameter size ly is less than 270 mm corresponds to an example that satisfies the requirements of the present invention.

(Transmission loss calculation and calculation results)
In the simulation, the transmission loss of sound passing through the ventilation holes 6 in the silencing system 1X shown in FIG. 14 was calculated. In the noise reduction system 1X, the total length of the ventilation hole 6 including the through hole 2a into which the ventilation sleeve 4 is inserted is 300 mm, and a cover member 12 (loud) and an air volume adjustment member 14 (register) are arranged at both end openings of the ventilation hole 6, respectively. It was modeled in this way. The diameter of the vent hole 6 was 100 mm on the front side, and was expanded to 150 mm near the rear end of the vent hole 6.

In the noise reduction system 1X shown in FIG. 14, sound waves are incident from a hemispherical sound wave incidence surface placed in a space on one side (outdoor side) of the ventilation hole 6, and a hemispherical sound wave incident surface placed in a space on the other side (indoor side) The amplitude per unit volume of the sound wave reaching the sound wave detection surface was determined. Each hemispherical surface has a radius of 500 mm centered on the central axis of the ventilation hole 6. The incident sound wave had an amplitude of 1 per unit volume. The value obtained by dividing the integral value of the sound pressure amplitude on the sound wave detection surface by the integral value of the sound pressure amplitude on the sound wave incidence surface, squared, was defined as the transmitted sound pressure intensity.

First, as a reference, the transmitted sound pressure was calculated for a configuration in which the silencer 10X was not disposed (hereinafter referred to as a straight tube configuration).
Next, the transmitted sound pressure was calculated while changing the diameter size ly of the first cavity 31 for the configuration in which the silencer 10X was arranged. Thereafter, using the transmitted sound pressure calculated for the straight pipe configuration as a reference, the difference in sound pressure level from the reference was calculated for each calculation result to calculate a normalized transmission loss (hereinafter referred to as transmission loss). The transmission loss was calculated within the 1/3 octave frequency band of the JIS standard.

Note that background correction was performed on the calculated value of transmission loss based on the measured value (experimental value) in a transmission loss measurement experiment described later. This is because it is difficult to calculate the transmission loss with such accuracy that the absolute values match between the calculated value and the experimental value. In the background correction, when the diameter size ly of the first cavity 31 is 270 mm, the transmission loss value in the 1/3 octave band (transmitted sound pressure difference) was used as the correction value.

In addition, for a frequency band corresponding to one 1/3 octave band, eight frequencies are set within that band, and the transmission loss is calculated at each of the eight points while changing the diameter ly, and the average value is calculated. (arithmetic mean value) was calculated. Furthermore, among the average values of transmission loss obtained at each of the eight points, the values of the points that are lower than the transmission loss when using a class T2 soundproof sash are added up, and the total value is calculated based on the class T2 soundproof sash. The difference from the standard (hereinafter referred to as the difference from grade T2) when
Note that the frequencies at the eight points mentioned above are determined empirically, and the scale of frequency intervals is not a linear scale but a log scale.

FIG. 15 shows the transmission loss calculated when the diameter size ly is 170 mm, 210 mm, and 270 mm. In FIG. 15, the transmission loss due to the soundproof sash of class T2 is shown by a broken line as a comparative value. In addition, the calculation result of the difference from class T2, specifically, the sum of the differences at all frequencies (in detail, 500Hz, 100Hz, etc.) where the calculated value of transmission loss was lower than class T2, is shown in Figure 16. Shown below.

As can be seen from FIG. 15, the sound transmission loss due to the silencer 10X is significantly reduced near 500 Hz and 1000 Hz. Here, among the resonances occurring in the vent hole 6, the frequency f2 of the second resonance is around 500 Hz, and the frequency f3 of the third resonance is around 1000 Hz. In other words, at each of the frequencies of the second resonance and the third resonance, the transmission loss due to the silencer 10X is greatly reduced, and as shown in FIG. be.

Here, the difference from the grade T2 shown in FIG. 16 is the sum of the differences between the transmission loss due to the silencer 10X and the transmission loss due to the soundproof sash of grade T2 at each frequency of the second resonance and the third resonance. show. As can be seen from FIG. 16, the difference from class T2 is -4 when the diameter size is 270 mm, which is the maximum. That is, in the comparative example, the transmission loss due to the silencer 10X is the lowest at each frequency of the second resonance and the third resonance, compared to the transmission loss due to the soundproof sash of class T2.
On the other hand, when using the silencer 10X with a diameter size ly smaller than 270 mm, that is, in the example of the present invention, the difference from the grade T2 becomes smaller as shown in FIG. It can be seen that the effectiveness has improved.

Further, for each of the second resonance frequency and the third resonance frequency, FIG. 17 shows the difference in transmission loss between the sound deadening device 10X of the example and the soundproof sash of class T2. As can be seen from Fig. 17, in the range where the diameter size ly is larger than 190 mm, the transmission loss increases at one resonance frequency and decreases at the other resonance frequency as the diameter size ly changes. The trade-off relationship is resolved.

In addition, in the simulation, the diameter size L was calculated for the silencer 110 of the reference example shown in FIG. The resonant frequency in each cavity 131, 132 was calculated while changing. The calculation results are shown in FIG. As shown in FIG. 18, in the noise damping device 110 of the reference example, the larger the diameter size L, the larger the resonance frequency in the cavities 131 and 132. On the other hand, over all diameter sizes L, the resonance frequency of the rear cavity having an opening 132a farther from the sound wave incidence surface is higher than the resonant frequency of the front cavity 131 having the opening 131a closer to the sound wave incidence surface. The resonant frequency at section 132 becomes higher.

Furthermore, in the simulation, the transmission loss when using the muffler 110 of the reference example in the muffler system 1X was calculated while changing the diameter size L, and the difference from the class T2 was determined from the calculation results. The difference from the determined grade T2 is shown in FIG. In the noise damping device 110 of the reference example, as shown in FIG. 19, the transmission loss at the frequencies of the second resonance and the third resonance is lower than that when a soundproof sash of class T2 is used, and the difference from class T2 is The diameter size L was approximately constant. That is, in the noise damping device 110 of the reference example, the sound damping effect at the frequencies of the second resonance and the third resonance is inferior to that of the soundproof sash of class T2, and the sound deadening effect does not improve even if the diameter size L is changed (that is, the sound deadening effect of the soundproof sash of class T2 does not improve). It was found that the difference from

(Transmission loss measurement experiment)
An environment to which the silencing system 1X shown in FIG. 14 was applied was constructed, and an experiment was conducted to measure the transmission loss of the silencing device 10X in the silencing system 1X. Specifically, the measurement environment shown in Fig. 20 was constructed, and the sound source speaker SP and microphone M1 were installed in one of two rooms (reverberation room R1) separated by a partition wall K with a thickness of 300 mm, and the sound source speaker SP and microphone M1 were installed in the other room. Microphone M2 was also installed in the room (semi-anechoic chamber R2). A correction constant was used to match the absolute value of the transmission loss measured by this method to the transmission loss measured in the "Method for measuring the air sound isolation performance of small building parts in the laboratory" specified in JIS A1428. The background values were corrected. Regarding the acquisition of the correction constant, using the same test specimen, the measurement according to the method shown in FIG. 20 and the measurement based on JIS A1428 were performed at an evaluation organization, and the difference between them was used as the correction constant.

The partition wall K is constituted by a wall k1 on the reverberation chamber R1 side and a wall k2 on the semi-anechoic chamber R2 side. A silencing system 1X shown in FIG. 14 is placed inside the partition wall K, and the silencing device 10X is installed between the two walls k1 and k2. In order to obtain the same configuration as shown in FIG. UNIX AG100A-AL) was installed. In addition, a resistor (KRP-BWF manufactured by UNIX Co., Ltd.) as an air volume adjustment member was attached to the through hole in the wall k2 on the side of the semi-anechoic chamber R2.

Then, while changing the diameter size ly of the first cavity part 31 in the silencer 10X, sound in a frequency band of 1/3 octave band is generated from the sound source speaker SP in the reverberation chamber R1, and the sound in the reverberation chamber R1 and the semi-anechoic chamber are The sound pressure level was measured in each room of R2 using microphones M1 and M2. Thereafter, transmission loss was determined (actually measured) based on the sound pressure level measured in each room. Furthermore, the difference from the grade T2 was determined for the actually measured transmission loss using the same procedure used to determine the difference from the grade T2 in the simulation described above.

FIG. 21 shows measured values of transmission loss when the diameter size ly is 180 mm, 210 mm, and 270 mm. Further, FIG. 22 shows the difference from the grade T2 determined based on the actually measured transmission loss. In addition, in FIG. 22, the difference from the grade T2 obtained by the above-mentioned simulation is also shown as a reference value.

As shown in Fig. 21, the measured values of transmission loss show the same tendency as the simulation calculation results, and decrease significantly near 500 Hz and 1000 Hz, which are the frequencies of the second resonance and third resonance, respectively, and as the diameter size ly In some cases, the transmission loss is lower than that of a class T2 soundproof sash.

Further, the difference from the grade T2 obtained from the measured value of transmission loss approximates the difference from the grade T2 obtained by simulation (calculation), as shown in FIG. In other words, when the resonant frequency fs1 in the first cavity 31 is higher than the resonant frequency fs2 in the second cavity 32, the silencing performance is improved compared to when the resonant frequency fs2 is higher than the resonant frequency fs1. This is clear from the actual loss measurement results.
Note that when the diameter size ly is 270 mm, that is, in the comparative example, the difference from the grade T2 is the same between the simulation and the experiment. This is because, as described above, background correction was performed on the simulation calculation results so that the simulation calculation results and the actual measured values in the comparative example matched.

As explained above, the embodiments of the present invention, that is, the cases where the diameter size ly of the silencer is smaller than the turning point, are all within the scope of the present invention, and the resonant frequency fs1 in the first cavity part The effect of the present invention is obvious because the silencing effect is improved as the resonance frequency fs2 becomes higher than the resonance frequency fs2 in the second cavity.

1, 1X sound deadening system 2 wall 2a through hole 4 ventilation sleeve 6 ventilation hole 8 decorative board 8a mounting hole 10, 10 28, 120 Silencer 28A First Silencer 28B Second Silencer 31 First Cavity 31a First Opening 32 Second Cavity 32a Second Opening 32b Rear 32c Front 32d Intermediate 34, 134 Sound Absorbing Material 36, 136 Partition wall 37 First partition wall piece 37a Projecting part 38 Second partition wall piece 39, 40 Annular wall 131, 132 Cavity part 131a, 132a Opening part K Partition wall k1 Wall body k2 Decorative board M1, M2 Microphone R1 Reverberation room R2 Semi-anechoic chamber SP sound source speaker

Claims (11)

A sound muffling device that muffles sound passing through a ventilation hole including a through hole in the wall is disposed on one side of the wall,
The muffler includes a plurality of cavities, an opening provided in each of the cavities and communicating the ventilation hole with the cavity, and a sound absorbing material disposed in each of the cavities. , each cavity resonates at a different frequency to muffle the sound,
Each of the hollow portions includes a portion located outside the ventilation hole in a cross direction that intersects an extending direction of the ventilation hole,
The openings of the respective cavities are located at different positions in the extending direction, and are connected to a resonant sound field space within the ventilation hole,
The plurality of hollow parts include a first hollow part and a second hollow part adjacent to each other in the extending direction,
A portion of the second cavity is located in a range where the first cavity exists in the extending direction,
A sound muffling device wherein a resonance frequency in the cavity having the opening closest to the wall is higher than a resonance frequency in the cavity having the opening farthest from the wall. The muffler according to claim 1, wherein the muffler has a partition wall that partitions the hollow portions from each other. The opening of the second cavity is further away from the wall than the opening of the first cavity,
The muffling device according to claim 1 or 2, wherein the second cavity portion has a bent shape. further comprising a ventilation section that is continuous with the internal space of the ventilation sleeve inserted into the through hole in the extending direction,
The muffler according to any one of claims 1 to 3, wherein the muffler is disposed at a position surrounding the ventilation section in the cross direction. The muffling device according to any one of claims 1 to 4, wherein the muffling device is arranged between the wall and a decorative board that is spaced apart from the wall in the extending direction. The muffling device according to any one of claims 1 to 5, wherein the number of the plurality of hollow parts is two. 7. The volume of the cavity having the opening furthest from the wall is larger than the volume of the cavity having the opening closest to the wall. Silencer. The partition wall has a first partition wall piece and a second partition wall piece extending from the first partition wall piece toward the wall along the extension direction,
The muffling device according to claim 2, wherein the first partition wall piece has a protruding portion that protrudes further outward than the second partition wall piece in the intersecting direction. The muffler does not resonate with the sound at the frequency of the first resonance occurring in the vent, and in the cavity having the opening farthest from the wall, the sound at the frequency of the first resonance does not resonate. A silencer according to any one of claims 1 to 8, which resonates at a high resonant frequency. Among the resonances in the ventilation hole, the frequency of the second resonance, which is the next highest resonance frequency after the first resonance, is f2, and the resonance frequency in the cavity having the opening farthest from the wall is fs2. The muffling device according to claim 9, wherein the resonance frequency fs2 satisfies 0.8×f2<fs2<1.2×f2. The muffling device according to claim 10, wherein the resonance frequency fs2 satisfies 0.9×f2<fs2<1.1×f2.