JPH0271300A - Sound absorbing body and sound absorbing duct using this body - Google Patents

Abstract

PURPOSE:To obtain a compact sound absorbing body whose damping effect is great for sounds in a wide band including a high frequency band by connecting not only resonance chambers but also the resonance chamber on the sound source side and the sound source space by resonance cylinders to form a multistage resonance type sound absorbing structure body different in resonance frequency. CONSTITUTION:With respect to a sound absorbing body 1, two stages of resonance chambers 2 and 3 are vertically provided, and respective resonance chambers 2a and 3 and a flow passage 4 of a fluid accompanied with noise are connected by resonance cylinders 5 and 6. That is, a two-stage resonance type Helmhortz resonator having two degrees of freedom is constituted, and the resonance frequency of this resonator is determined by capacities of resonance chambers 2 and 3, diameters D of resonance cylinders 5 and 6, and a length L of neck parts (the length from entrances to exists of resonance cylinders). Consequently, these elements are properly designed to damp the noise of arbitrary frequency. Thus, this resonator displays the damping effect throughout a wide band regardless of the compact structure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to sound-deadening and sound-absorbing elements used to attenuate duct noise, building noise, and other general noise. More specifically, the present invention relates to a reactive sound absorber and a sound absorbing duct using the same.

(Conventional technology) Silencers are generally classified into two types: ■Sound absorbing type mufflers and ■Reactive type mufflers. Sound-absorbing mufflers utilize the sound-absorbing effects of fibrous sound-absorbing materials such as glass wool and porous plates, and are particularly effective at attenuating mid- to high-frequency sounds. It has the characteristic that it increases and decreases almost monotonically.

On the other hand, reactive silencers use sound wave interference and resonance phenomena to attenuate sound, and are particularly effective at attenuating low to mid-range sounds, and are effective at reducing sound at specific frequencies determined by the structure, etc. It has the characteristic of having a spot-wise damping effect.

Therefore, conventionally, reactive mufflers and sound absorbing mufflers have been used depending on the peak frequency band of the noise and its width, or they have been used in combination.

(Problem to be Solved by the Invention) However, in recent years, the application conditions for silencers have become stricter year by year, and their use in high-temperature hot water, extremely low wet areas, and high-speed gas flow hot water has increased. Under these conditions, it is difficult to apply conventional fiber sound absorbing materials. In addition, porous materials such as ceramics have begun to be used as an alternative, but they have drawbacks such as low sound absorption, large weight, and high cost.

In addition, in the case of a reactive silencer, as shown in Figure 2 (A), its sound reduction characteristics have a steep slope with a peak at a specific frequency determined by conditions such as the volume of the silencer, the inlet diameter, and the length of the silencer. Since it exhibits a damping characteristic that draws an eyelid curve, it has the disadvantage that the sound reduction effect is greatly reduced if the frequency deviates slightly from the resonant frequency. For this reason, the conventional glue active type muffler has the drawback that it requires a combination of many mufflers with different characteristics in order to accommodate a wide band, and that it takes up space and is bulky.

Furthermore, in conventional adhesive active silencers, compact sound absorbing bodies with excellent sound absorption characteristics in low frequency bands are not found.

SUMMARY OF THE INVENTION An object of the present invention is to provide a compact or active type sound absorber that has a large damping effect on wide-band sound including high frequency ranges, and a sound absorbing duct using the same. Another object of the present invention is to provide a reactive sound absorber that is more compact than conventional sound absorbers and has a high sound reduction effect in a low frequency band, and a sound absorbing duct using the same.

(Means for Solving the Problems) In order to achieve the above object, the sound absorber of the present invention has at least two or more stages of resonance chambers stacked one on top of the other in a direction perpendicular to the direction of fluid flow, and these resonance chambers are stacked on top of each other in a direction perpendicular to the direction of fluid flow. The resonance chamber on the sound source side and the sound source space are communicated with each other through a resonance cylinder, and a multi-stage resonant sound absorbing structure having different resonance frequencies is formed.

Further, the sound absorber of the present invention has at least two or more stages of resonance chambers stacked one on top of the other, and the resonance chambers are opened to each other and to the external space and the adjacent resonance chamber in a direction perpendicular to the fluid flow. That's what I do.

Further, in the sound absorbing body of the present invention, a resonance cylinder is provided in a resonance chamber disposed along a noisy flow so as to be perpendicular to the flow of the fluid, and the resonance cylinder is provided to penetrate the resonance chamber in a direction perpendicular to the flow of the fluid. I try to open it by opening it.

Further, the above-described sound absorbing body of the present invention constitutes a sound absorbing panel by arranging it in a plane, and furthermore, this sound absorbing panel is installed in a duct along the flow, and the opening of the resonance chamber is arranged in a direction perpendicular to the flow. This creates a sound-absorbing duct.

In addition, cells in which at least two or more resonance chambers are stacked in the radial direction are arranged in the circumferential direction and the axial direction to form a cylindrical body with a flow path formed inside, and the resonance chambers of each cell are connected to each other and the flow path is connected to each other. adjacent resonance chambers, or for some cells, inner flow channels or outer flow channels and adjacent resonance chambers, or inner and outer flow channels and adjacent resonance chambers, respectively, in a direction perpendicular to the flow. A cylindrical sound absorber is constructed by communicating through a resonance cylinder.

Therefore, a sound-absorbing duct is constructed by stacking these cylindrical sound-absorbing bodies in bales or in series inside the duct. Further, in the sound absorbing body of the present invention, the resonance cylinder is made into a slit parallel to the direction of flow, or is made separate from the cells constituting the resonance chamber so that it can be attached and detached. Furthermore, the sound absorber of the present invention is characterized in that a thin film is attached to the entrance of the resonance chamber.

(Function) Therefore, only sound is present in the stacked resonance chambers, causing multiple resonances in the multi-stage resonators with different degrees of freedom and different damping characteristics. Therefore, the drop in the amount of attenuation in a frequency band far from the resonant frequency of each resonator is raised to obtain a damping characteristic that gradually decreases. That is, FIG. 2(B), <C
) If resonant sound-absorbing structures having resonance frequencies of fol and f02 are formed independently of each other, as shown in Figure 2, the damping characteristics will be as shown by the imaginary line, or if multiple resonances are caused, the damping characteristics will be as shown by the solid line. A damping effect is obtained in a frequency band far from the two resonant frequencies, especially between the two resonant frequencies, and approaches the damping characteristics of a silencer using a sound absorbing material.

When the resonant frequencies are brought close to each other to a certain extent, the sharp frequency characteristics mentioned above are relaxed and a muffler with a wide damping effect is obtained, and when the resonance frequencies almost overlap, the amount of attenuation increases.

In addition, when the sound inlet of the resonance chamber is opened in a direction perpendicular to the flow of fluid and the noise is allowed to flow in from both ends of the resonance chamber,
An increase in the amount of attenuation is observed, and the increase in the amount of attenuation in the low frequency band is particularly noticeable during single resonance.

(Example) Hereinafter, the configuration of the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 shows the principle of the sound absorber of the present invention. This sound absorber 1 has resonance chambers 2 and 3 stacked in two stages, and each resonance chamber 2 and 3 and a flow path 4 for a noisy fluid are communicated through a 1% cylinder 5.6. That is, it constitutes a two-degree-of-freedom two-stage resonant Helmholtz resonator. The resonance frequency of the Helmholtz resonator is determined by the volume of the resonance chamber 2.3 and the hole diameter of the resonance tubes 5 and 6 (
D), Neck length (length from inlet to outlet of resonance tube: I
−) is determined by Therefore, by appropriately designing these elements, it is possible to attenuate noise at any frequency. Moreover, this multi-stage resonant sound absorbing structure causes multiple resonances, prevents a sudden drop in the attenuation rate in a frequency band far from the resonant frequency peculiar to a Helmholtz resonator, and obtains a damping characteristic that widens the band in which the damping effect is achieved.

Therefore, if the resonance frequency of each stage resonator is set appropriately within the range where the multiple resonance effect exists, centered around the peak frequency of the noise that is intended to attenuate, the resonance frequency of the resonator at each stage can be set appropriately within a range that has a multiple resonance effect. Attenuation characteristics that increase and decrease almost monotonically can be obtained.

In addition, in this sound absorbing body 1, in the case of this embodiment, the resonance cylinders 5 and 6 that constitute the resonance hole 7 and the neck portion 8 are formed in a side structure and are detachable from the shell 13 that constitutes the resonance chamber as shown in the figure. It is designed so that the resonant frequency can be easily changed by replacing it with another resonant cylinder with a different inner diameter or neck length.

Of course, if there is no need to change the resonant frequency,
The resonance cylinders 5 and 6 may be integrally molded with the cell 13 constituting the resonance chamber 2.3. Moreover, the resonance tubes 5 and 6 may not be attached depending on the set resonance frequency. In this case, the hole drilled in the wall of the shell 13 on the inlet side substantially functions as a resonator cylinder. That is, this hole is a resonance cylinder integrated with the shell 13. In addition, when fluid flow is involved,
As shown in FIG. 7, a thin film 9 is attached to the sound inlet of the resonance chamber 2 on the side of the sound source or flow path 4, such as the resonance hole 7 of the co-polymer cylinder 5, to prevent the flow from flowing into the cylinder. It is provided.

When a flow enters the resonance chamber, a standing vortex is generated at the inlet, inhibiting acoustic resonance and generally reducing damping characteristics. Therefore, the thin film 9 attached to the entrance of the resonator cylinder 5 needs to be made of a thickness and material that prevents the inflow of the flow and does not impede the inflow of the sound. It is preferable to use Lamiho 1-paper such as - Plus Deck film such as Lafluoroethylene (trade name, Teflon), Japanese paper, felt, metal foil.

Further, in the case of this embodiment, the resonance chambers 2 and 3 have the same cross-sectional area perpendicular to the axis, but have different volumes by varying the depth. Of course,
It is also possible to make the volumes of both resonance chambers 2 and 3 the same6.In addition, in the case of this embodiment, the volume of the resonance chambers is either constant or variable using bellows, a mold, etc. It is also possible. The sound absorbing body 1 configured as described above can be directly buried in the wall surface of a structure to form a sound absorbing wall, assembled in large numbers and fixed to a frame to form a panel, or arranged in large numbers in a cylindrical shape to absorb sound. It is also possible to form a duct by itself, or to form a cylindrical sound absorbing body, and further to combine these panels to form a composite sound absorbing panel, or to configure a sound absorbing duct by placing them in a duct.

FIG. 3(A) shows an example of a sound absorbing panel using the above sound absorbing body. This sound-absorbing panel 10 is constructed by arranging a large number of sound-absorbing bodies 1 in which resonance chambers 2 and 3 are stacked in two or more stages in a grid pattern on a base within a frame 11. The sound absorbers 1 formed in one panel may have the same attenuation characteristics, or may be a combination of several groups with different attenuation characteristics, or all sound absorbers with different attenuation characteristics. This sound-absorbing panel 10 forms a resonance chamber by combining frame plates 11A and 11B that can be fitted in a grid-like manner, for example, as shown in FIGS. 4(A) and 4(B). It is produced by

That is, the frame plates 11A and I are equal to the length of one side of the panel 10.
By providing slits 12 at regular or predetermined intervals in the IB and combining them by fitting the slits 12, a large number of cells 13 with the same resonance volume or a large number of cells with different resonance volumes partitioned into a square pattern can be formed. cell 1
3. Next, a panel 15 formed by drilling holes 14 into which the resonance tubes 5 are inserted at positions corresponding to each cell is placed on top of the cells 13 to form the frame plate 11A.

11B to form the second stage resonance chamber 3.

Then, a predetermined resonance tube 5 is fitted into each person 14.

Next, the shell 13 formed by combining the comb-tooth frame plates 11A11B is again placed on the panel 15, and the panel 16 is further joined to form the first stage resonance chamber 3. And each person 14
A predetermined resonator cylinder 4 is fitted into the resonator tube 4.

In addition, as shown in FIGS. 5(A) and 5(B), the resonance cylinder 5.6
It is also possible to form the resonance chamber 2.3 by arranging a large number of small cylinders 17 in the frame 11, each having a hole 18 for inserting the cylinder.

In this case, by changing the diameter of the cylinder 17, it is possible to easily form multiple resonance chambers with different resonance volumes within one panel.

An example of a composite sound absorbing panel is not shown in FIG. 3(B). This composite sound-absorbing panel is constructed by selectively combining the sound-absorbing panels shown in FIG. The panel can be used as a shield against a sound source, or can be used as a sound insulating board that absorbs the noise of a traveling vehicle by being installed oppositely on both ends of a road or the like.

FIG. 6 shows an embodiment of a sound absorbing duct using the sound absorbing body of the present invention. This sound absorbing duct is constructed by installing the sound absorbing panel 10 configured as described above inside the duct 19 along the flow of fluid. In this case, it is preferable that the sound absorbing panels 10 are installed facing each other so that fluid flows between them. The narrower the installation interval of the sound absorbing panels 10, the more effective it is at attenuating sound. In particular, the highest attenuation effect can be obtained when the interval is equal to 1/2 wavelength of the noise.

Other embodiments are shown in FIGS. 9(A) and 9(B). In this embodiment, a duct 20 is formed by arranging the sound absorbers 1 shown in FIG. 1 in a ring shape. For example, at least two or more stages of resonance chambers 23 may be overlapped in the radial direction, and each resonance chamber 2
, 3 connected by a resonant cylinder 56 are arranged circumferentially in large numbers to form a cylindrical body, and a flow path 4 for a noisy fluid is formed inside the cylindrical body. The sound absorbing cells 13 constituting the duct are acoustically independent from each other in the circumferential direction and the axial direction, and are open on the side corresponding to the inner circumferential surface of the duct, and are perpendicular to the fluid flowing in the inner flow path 4. The resonance chambers 2.3 and 2.3 are placed one on top of the other in the direction of the sound, and only the sound is transmitted through the resonance chambers 2.3 and 2.3.
It is designed to fit inside 3. In this case, duct 2
Since the fluid flows in the resonator cylinder 5, it is preferable to attach a thin film 9 to the inlet of the resonator tube 5 on the flow path 4 side, as shown in FIG. 7, in order to prevent the generation of standing vortices.

Further, other embodiments are shown in FIGS. 10(A) and 10(B). In this embodiment, the sound absorbers 1 shown in FIG. 1 are arranged in an annular manner, and the sound inlets of some of the sound absorbers are in the inner flow path, and the sound inlets of the remaining part of the sound absorbers are in the outer space 22. The sound absorber 21 has a cylindrical shape and is open toward the sound absorber 21 .

FIG. 11 shows another embodiment of the present invention. This sound absorber is
The sound absorber shown in Figure 1 is a semi-closed type, with the sound entrance limited to one side, whereas it is a completely open type with sound entrances opening to both the external space and the adjacent resonance chamber; This allows sound to enter from the sides as well.

That is, at least two or more stages of resonance chambers 2 and 3 are provided one on top of the other, and these resonance chambers 2 and 3 are communicated with each other through a resonance tube 6, and the resonance chambers 2 and 3 adjacent to the external space 4.22 are connected to each other through a resonance tube 5.
Alternatively, the resonance chambers 2 are stacked and communicated by 632.
, 3 with sound inlets at both ends. The resonance frequency of this sound absorber is determined by the diameter of the resonance hole 7 with a resonance fi of 5.6, the length of the neck part 8 below the neck, the dimensions of the resonance chamber 2.3, etc. It is also similar to molding the resonance tube 5 or 6 separately from the cell 33 so that it can be replaced.

FIG. 12 shows another embodiment. In this embodiment, the sound absorber 31 shown in FIG. 11 is used to construct a cylindrical sound absorber 36 suitable for filling as a muffler in a large duct.

This sound absorber forms a cylindrical body in which a large number of acoustically independent resonance cells 33 are arranged in the circumferential direction and the axial direction, and constitutes one sound absorber as a whole. In the resonance cell 33, at least two or more stages of resonance chambers 2.3 are arranged one on top of the other in the radial direction, and the resonance cylinders 5, 6 and the hole 32 extend through the resonance cell 33 in the radial direction. Therefore, for the fluid flowing in the flow v@4 inside the cylindrical sound absorber 35 formed by the set of cells 33 constituting the multistage resonance chamber and the fluid flowing along the cylindrical sound absorber 35 in the outer space 22, The resonance chambers 2 and 3 and the sound input lower 32 are arranged one on top of the other in orthogonal directions.

Therefore, noise is transmitted from the inside and outside of the cylindrical sound absorber 35 to the resonance chamber 2.3.
The sound goes inside, causes multiple resonances, and is attenuated. Resonance cylinders 5, 6 are preferably cell members 3 constituting a resonance chamber 2.3.
It is formed separately from the resonance chambers 2 and 3, and is provided in a detachable manner with respect to the resonance chambers 2 and 3. This makes it possible to change the resonance frequency by appropriately changing the diameter D of the resonance hole 7 of the resonance cylinders 5, 6, the length of the neck portion 8 below the neck, etc. Of course, it is also possible to form it integrally with the member 33 that constitutes the resonance chambers 2 and 3.

FIG. 15 shows another embodiment. This embodiment uses a completely open single-stage resonance chamber to enhance the sound reduction effect in the low frequency band. This sound absorber 41 is provided with a single-stage resonance chamber 2 which is hollow in a direction perpendicular to the flow of fluid, and a resonance tube 5 is provided at at least one of the sound inlets 42 of the resonance chamber 2. As in the embodiments described above, the resonance tube 5 is formed separately from the cell 43 constituting the resonance chamber 2 and is detachable, or is formed integrally with the cell 43. In addition, the resonance chamber 2 has a lower part where the sound enters in the direction perpendicular to the flow,
2 is provided and opened so that sound can enter the resonance chamber 2 in a direction perpendicular to the flow of fluid. The diameters of the sound entrance hole 7, that is, the resonance hole and the hole 42 are determined in relation to the set resonance frequency as described above.

Further, FIG. 16 shows another embodiment. This example is the first
A cylindrical sound absorber 45 that is effective in attenuating low frequency bands is constructed using the sound absorber shown in FIG. 5. The sound absorbing body 45 has resonance chambers 2 that are acoustically independent from each other arranged in the circumferential direction and the axial direction, and is formed into a cylindrical body as a whole. Each resonance chamber 2 is provided with a resonance cylinder 5 and a hole 42 so as to penetrate in the radial direction, and is provided so as to take in sound in a direction perpendicular to the fluid flowing in the space 422 inside the cylindrical sound absorber 45.

The sound absorbers shown in FIGS. 11 and 15 can be arranged in large numbers in a plane like the sound absorbers shown in FIG.
As shown in the figures and FIG. 17, sound absorbing panels 36, 46, sound absorbing walls, etc. can also be constructed.

Also, a cylindrical sound absorber 35.45 formed using the sound absorber 3141 not shown in FIG. 11 or FIG. The sound absorbing duct 50 can be constructed by installing them so that their longitudinal directions coincide. At this time, the cylindrical sound absorbers 35 or 45 are stacked in the duct 51 in a staggered arrangement [FIG. 13(A)] or in a series arrangement [FIG. 13(B)]. In this case, in addition to the flow path 4 in each cylindrical sound absorber 35.45, a substantially triangular or rhombic flow path 22 is formed between the sound absorbers 35.45.

It should be noted that the above-described embodiment is one of the preferred embodiments, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, although the resonance cylinders 5 and 6 are described as having a cylindrical shape with flanges, they may also have slits. In this case, by arranging the slits parallel to or perpendicular to the flow direction, similar damping characteristics can be obtained without the need for multiple stages of fine resonance chambers, making it possible to produce sound-absorbing panels easily and at low cost. can be done. Furthermore, if the shell 13 that partitions the resonance chamber 2.3 is made of a bellows or the like and made movable to make the resonance volume variable, and/or the neck length and inner diameter of the resonance tubes 5 and 6 can be made variable. Then, since the resonant frequency can be changed during use, an active control type muffler can be constructed. Furthermore, although the resonance chambers 2.3 are formed in two stages in this embodiment, they are not limited to this, and may be formed in three or more stages.

Since the sound absorber of the present invention is configured as described above, it is a reactive type sound absorber and has a compact structure, yet can exhibit a damping effect over a wide band. For example, FIG. 8 shows an example of an experiment conducted on the sound absorbing duct shown in FIG. 6.

(Effects of the Invention) As is clear from the above description, the sound absorber of the present invention has at least two or more stages of resonance chambers stacked in a direction perpendicular to the direction of fluid flow, and these are communicated through a resonance cylinder. ,
Since the resonant sound absorbing structures with different resonant frequencies are formed in multiple stages, multiple resonances occur, and even in frequency bands that deviate from the resonant frequency of each resonator, the drop in attenuation is gradual, resulting in attenuation that is effective over a wide range. Characteristics can be realized with a reactive type. Such characteristics can be achieved by a combination of conventional single-stage resonators, or if the same characteristics are obtained, the present invention can be made more compact. In addition, in the sound absorbing body of the present invention, if the resonance tube is made to be detachable from the shell, the damping characteristics can be easily changed by replacing the resonance tube with a different size, and the sound absorbing body can be easily and inexpensively changed. I can produce it. In addition, in the sound absorber of the present invention, the misalignment of the thin film at the entrance of the resonance cylinder on the flow path side can prevent the flow from flowing into the resonance chamber when accompanied by a flow, suppress the generation of standing vortices, and improve the damping properties. can prevent deterioration.

Furthermore, by combining sound absorbers with different attenuation characteristics, it is possible to easily create a sound absorbing panel that can attenuate in a wide band and has the desired performance despite its compact structure. Furthermore, when a sound-absorbing duct is constructed by arranging sound-absorbing panels along the flow inside the duct, it has the same damping effect as a sound-absorbing duct using a fibrous sound-absorbing material such as crow wool, in other words, it can reduce noise only at a specific frequency. It is possible to achieve a damping effect on a wide range of sounds including high frequencies. Furthermore, this sound-absorbing duct itself is less affected by aging and moisture than fiber sound-absorbing materials, so it is not restricted by usage conditions and can be used in high-temperature hot water, extremely low wet areas, high-speed flow fields, etc. It is. Furthermore, it is lighter and cheaper than sound absorbing materials such as ceramics, and has a high damping effect.

In addition, in the sound absorbing body of the present invention, the sound entrance and exit port of the resonance chamber is provided so as to penetrate in a direction perpendicular to the flow, so that noise enters from both sides and causes multiple resonance, so the resonance frequency remains the same. The volume reduction is considerably greater than that in the case where there is a large opening. If the volume reduction is kept the same, the cylindrical sound absorber can be made shorter and more compact. For example, when these cylindrical sound absorbers are stacked in a staggered or series manner in a duct, such as a floor exhaust duct, the noise not only flows through the flow path inside the cylindrical sound absorbers, but also forms in the gaps between adjacent sound absorbers. Since the noise of the flow passing through the flow path simultaneously enters the resonance chamber and causes multiple resonances, the resonance frequency does not change, but the volume reduction increases significantly.

Further, when the silencer of the present invention is arranged in an annular shape to form a cylindrical body to form a duct, it is possible to suppress the generation of noise without causing a large pressure loss.

In addition, if an opening in the direction perpendicular to the flow is provided in the -stage resonance chamber to allow sound to enter, either attenuation in the high frequency band is not expected, or resonance frequency is obtained in the low frequency band, and the volume is reduced. Since it increases significantly, the length of the cylinder can be shortened and made compact.

[Brief explanation of the drawing]

Figure 1 (A) is a central vertical cross-sectional view showing the principle of sound absorbing material.
Figure (B) is a perspective view of the resonator cylinder, Figure 2 (A) is a graph showing the sound reduction characteristics of the conventional glue active type silencer, Figure 2 (B)
), (C) are graphs showing the sound reduction characteristics of the present invention, and Figure 3 (
A) is a perspective view showing the appearance of the sound absorbing panel, FIG. 3(B)
is a perspective view showing an example of a composite sound-absorbing panel made by further combining the same panels, FIG. 4(A) is a plan view of the sound-absorbing panel, and FIG.
B) is a schematic sectional view taken along the line ■-IV, FIG. 9 is a perspective view showing an example of a sound absorbing duct, FIG. 7 is a central vertical sectional view showing the principle of another embodiment of the sound absorbing body, and FIG. 8 is a graph showing the damping effect of the sound absorbing duct. ) (B) shows an example of the cylindrical sound absorber, (A) is a cross-sectional view, and (B) is a longitudinal cross-sectional view of the central half. Another embodiment is shown, in which (A) is a cross-sectional view, and (B) is a central half longitudinal cross-sectional view. Fig. 11 is a central longitudinal cross-sectional view showing the principle of another sound absorber of the present invention, and Fig. 12 is a vertical cross-sectional view. (A) and (B) show an example of a cylindrical sound absorber using the sound absorber shown in FIG. )
, (B) is an explanatory diagram of an embodiment in which a cylindrical sound absorber is arranged in a duct, FIG. 14 shows an example of a sound absorbing panel using the sound absorber of FIG. 11, (A) is a cross-sectional view, and (B) ) is a front view. Fig. 15 is a central vertical sectional view showing the principle of another sound absorber, Figs. 16 (A) and (B) show an example of a cylindrical sound absorber using the sound absorber of Fig. 15, and (A) is a cross-sectional view. Front view, (B)
is a vertical cross-sectional view taken in half. FIGS. 17(A) and (B) show an example of a sound absorbing panel using the sound absorbing body shown in FIG. 15, where (A) is a cross-sectional view;
B) is a front view. 1.31.41...Sound absorber, 2.3...Resonance chamber, 5
．． 6 Resonance cylinder, 7... Resonance hole, 8... Neck, 9...
Thin film, 0.36.46... Sound absorbing panel, 11... Frame, 3 17 33 43... Cell, 8... Frame for composite sound absorbing panel, 1... Duct, 0
...Duct, 35.45...Cylindrical sound absorber, 0...
Sound absorbing duct.

Claims (1)

[Scope of Claims] (1) At least two or more stages of resonance chambers are provided one on top of the other in a direction perpendicular to the direction of fluid flow, and these resonance chambers and the resonance chamber on the sound source side and the sound source space are communicated by a resonance cylinder. let me,
A sound absorbing body characterized by forming a multi-stage resonant sound absorbing structure having different resonance frequencies. (2) A cylindrical body in which cells in which at least two or more resonance chambers are stacked in the radial direction are arranged in the circumferential direction and the axial direction to form a flow path inside, and the resonance chambers of each cell are connected to each other and the flow path is connected to each other. A sound absorbing body characterized in that an adjacent resonance chamber is communicated with a resonance cylinder in a direction perpendicular to the flow of fluid. (3) A cylindrical body in which cells in which at least two or more resonance chambers are stacked in the radial direction are arranged in the circumferential direction and the axial direction to form a flow path inside, and some of the cells are arranged between the resonance chambers and inside. A sound absorbing body characterized in that the flow path and the adjacent resonant chamber are communicated with each other in some cells and with the outer space through a resonant tube in a direction perpendicular to the flow of the fluid. (4) Sound absorption characterized by providing at least two or more stages of resonance chambers stacked one on top of the other, and opening the resonance chambers with each other, the external space, and the adjacent resonance chamber with a resonance cylinder in a direction orthogonal to the flow of fluid. body. (5) A cylindrical body in which cells in which at least two or more stages of resonance chambers are stacked in the radial direction are arranged in the circumferential direction and axial direction to form a flow path inside, and the resonance chambers of each cell are mutually connected and the cells of the cylindrical body are A sound absorbing body characterized in that inner and outer spaces and adjacent resonance chambers are opened by a resonance cylinder in a direction perpendicular to the flow of fluid. (6) A resonance chamber arranged along the noisy flow is provided with a resonance cylinder perpendicular to the flow of the fluid, and the resonance chamber is opened by penetrating the resonance chamber in a direction perpendicular to the flow of the fluid. Sound absorber. (7) A cylindrical body in which a large number of acoustically independent resonance chambers are arranged circumferentially and axially to form a flow path inside, and each resonance corresponds to the circumferential surface and outer circumferential surface of the cylindrical body. A sound absorber characterized by having a resonant tube opened in a radial direction perpendicular to the flow of fluid on the surface of a chamber. (8) A sound absorbing body characterized in that a large number of the sound absorbing bodies according to claim 1, 4, or 6 are arranged on one plane to form a panel shape. (9) The sound absorber according to any one of claims 1 to 8, wherein the resonance cylinder is a slit parallel to the direction of fluid flow. (10) Claims 1 to 9, wherein the resonance tube is separate from the shell constituting the resonance chamber and is detachable.
The sound absorber according to any of the above. (11) The sound absorber according to any one of claims 1 to 10, characterized in that a thin film is attached to the sound inlet of the resonance chamber disposed on the side of the fluid flow path. (12) The panel-shaped sound absorber is installed in a duct along the flow of fluid, and the opening of the resonance chamber is arranged in a direction perpendicular to the flow. The sound absorbing duct described in any of the above. (13) Claim 1 characterized in that the panel-shaped sound absorbers include at least two panel-shaped sound absorbers, each set being installed facing each other across the flow.
The sound absorbing duct described in 2. (14) The sound absorbing body according to any one of claims 3, 5, 7, 9, 10, or 11 is arranged in a duct parallel to the flow direction and stacked in bales to fill the inside of the duct. Sound absorbing duct. (15) A sound absorber characterized in that the sound absorber according to any one of claims 3, 5, 7, 9, 10, or 11 is arranged in a duct parallel to the flow direction and stacked and packed in series. duct.