JP2005031240A - Panel and device for sound absorption - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a panel and a device for sound absorption which has superior sound absorbing performance. <P>SOLUTION: A sound absorbing panel 30 arranged in front of a rigid wall 20 at a specified interval has many through hole parts 40. Each through hole part 40 has a large hole part 41 exposed at least on one surface side of the sound absorbing panel 30, and also has a fine hole part 42 whose hole section is made smaller than the large hole part 41 at least at part of the hole part 40 along the plate thickness. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sound absorbing panel and a sound absorbing device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known a sound absorbing device configured by arranging a thin plate (sound absorbing panel) provided with a large number of fine holes at a predetermined interval on the front surface of a rigid wall (see Non-Patent Documents 1, 2, and 3 below). .
[0003]
[Non-Patent Document 1]
Maa Dah-you, “Theory and design of microperforated panel sound-absorbing constructions”, SCIENTIA SINICA, Jan-Feb, 1975, pp 55-71.
[0004]
[Non-Patent Document 2]
Maa DY, “Potential of microperforated panel absorber”, J. Am. Acoustic. Soc. Am. , 104 (5), Nov. 1998, pp2861-2866.
[0005]
[Non-Patent Document 3]
Jinkyo Lee and George W. Swenson, “Compact Sound Absorbers for Low Frequency”, Noise Control Engineering Journal, Vol. 38, No3, pp109-118
[0006]
[Problems to be solved by the invention]
However, in the sound absorbing device having such a structure, in order to obtain a suitable sound absorbing performance, the fine holes are very small, for example, 1 mm or less in diameter, and the thickness of the sound absorbing panel is made thin enough to be close to the diameter of the fine holes. Is required. For this reason, a reinforcing rib or the like is required for the sound absorbing panel. However, if this reinforcing rib is disposed, a fine hole cannot be provided at that location, which causes a decrease in sound absorbing performance.
[0007]
The present invention has been made in view of the above problems, and an object thereof is to provide a sound absorbing panel and a sound absorbing device excellent in sound absorbing performance.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a sound absorbing panel disposed on a front surface of a rigid wall at a predetermined interval, wherein a plurality of hole portions penetrating in the plate thickness direction are provided. The large hole portion is exposed on at least one side of the sound absorbing panel, and at least a part of the large number of hole portions in the plate thickness direction is provided with a fine hole portion whose hole cross-section is narrower than the large hole portion. It is characterized by that.
[0009]
According to such a sound absorbing panel, it is possible to obtain the strength by securing the thickness of the sound absorbing panel, and it is possible to obtain excellent sound absorbing performance by combining the large hole portion and the fine hole portion. Particularly excellent sound absorbing performance can be obtained in a low frequency region.
[0010]
That is, the air in the large hole portion is added as an additional mass (mass reactance), thereby lowering the resonance frequency of the resonance type sound absorbing structure formed by the hole portion and the back layer. This makes it possible to obtain excellent sound absorption performance particularly in a low frequency range. In order to improve the sound absorption characteristics in the low frequency range in the conventional sound absorbing structure of this type, it has been necessary to increase the thickness of the back air layer, but according to the present invention, the low frequency range can be achieved without increasing the thickness of the back air layer. It is possible to improve the sound absorption characteristics. In addition, the slight viscous resistance generated in the large-diameter part is expected to slightly increase the resistance component of the resonance type sound absorbing structure. As a result, the resonance characteristic is broadened, so that the sound absorbing characteristic is broadened and a wider frequency range is obtained. It is also expected that higher sound absorption performance can be obtained in the range.
[0011]
Further, in such a sound absorbing panel, it is desirable that the fine hole portion is provided so as to be exposed on one side of the sound absorbing panel.
[0012]
If it does in this way, since a large hole part should just be provided only in the single side | surface side of a sound absorption panel, a process can be performed easily.
[0013]
In such a sound absorbing panel, it is desirable that the fine hole portion is provided so as to be exposed on the front side of the sound absorbing panel.
[0014]
If it does in this way, the suitable external appearance from the front side can be obtained. Moreover, it can reduce that dust etc. penetrate | invade from a hole.
[0015]
In such a sound absorbing panel, it is desirable that the large hole portion has a constant hole cross section up to a predetermined depth in the plate thickness direction.
[0016]
If it does in this way, while processing a large hole part will become easy, more outstanding sound absorption performance can be obtained.
[0017]
In such a sound absorbing panel, it is desirable that the equivalent diameter of the hole cross section of the large hole portion is 1.5 times or more and 15 times or less of the equivalent diameter of the hole cross section of the fine hole portion.
[0018]
If it does in this way, suitable sound absorption performance can be obtained.
[0019]
In the present invention, the equivalent diameter of the hole cross section means four times the value obtained by dividing the cross sectional area by the perimeter.
[0020]
The sound absorbing device according to the present invention includes a rigid wall, any one of the above sound absorbing panels, and holding means for holding the sound absorbing panel on a front surface of the rigid wall at a predetermined interval. To do.
[0021]
According to such a sound absorbing device, excellent sound absorbing performance by the above sound absorbing panel can be realized.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0023]
FIG. 1 is a partial cross-sectional perspective view of a sound absorbing device 10 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional explanatory view of the sound absorbing device 10.
[0024]
As shown in FIG. 1, the sound absorbing device 10 includes a rigid wall 20 made of an acoustically strong material, a sound absorbing panel 30 provided with a large number of holes 40. A holding member (holding means) 50 for holding the sound absorbing panel 30 is provided at the interposed position.
[0025]
The holding member 50 is attached to the front surface side of the rigid wall 20, and the sound absorbing panel 30 is attached to the front end edge portion thereof by, for example, screwing. The interval between the rigid wall 20 and the sound absorbing panel 30 is appropriately set so that the required sound absorbing performance and the like can be obtained.
[0026]
As shown in FIG. 2, the holes 40... Penetrate through the sound absorbing panel 30 in the thickness direction, the large holes 41 are exposed on at least one side of the sound absorbing panel 30, and the sound absorbing panel 30. At least part of the plate thickness direction is provided with a fine hole portion 42 whose hole cross section is narrower than the large hole portion 41.
[0027]
If the hole 40 is constituted by the large hole portion 41 and the minute hole portion 42 in this way, a sufficiently small minute hole portion 42 is formed, and a sound absorbing effect by the minute holes is obtained, and the plate thickness of the sound absorbing panel 30 is secured. Strength can be obtained.
[0028]
Further, as will be described later, an excellent sound absorbing performance can be obtained by the combination of the large hole portion 41 and the fine hole portion 42. Particularly excellent sound absorbing performance can be obtained in a low frequency region.
[0029]
In the example of FIG. 2, the large hole portion 41 is provided on the front side of the sound absorbing panel 30, that is, on the opposite side of the rigid wall 20 so that the circular hole cross section is constant up to a predetermined depth. Although it is provided so as to penetrate from the bottom surface of the portion 41 to the back side of the sound absorbing panel 30, the shape of the hole portion 40 is not limited to this.
[0030]
For example, as shown in FIG. 3A, even if the large hole portion 41 is provided on the front side of the sound absorbing panel 30 and the fine hole portion 42 is provided on the back side, as shown in FIG. Even if the large hole portion 41 is provided on the back side and the fine hole portion 42 is provided on the front side, or as shown in FIG. 3C, the large hole portions 41 and 41 are provided on both the front side and the back side. The fine hole portion 42 may be provided in an intermediate portion of the thickness of the sound absorbing panel 30.
[0031]
As shown in FIG. 3, when the hole cross section of the large hole portion 41 is made constant to a predetermined depth, the processing of providing the large hole portion 41 in the sound absorbing panel 30 is facilitated, and more excellent sound absorption performance can be obtained. .
[0032]
In particular, when the fine hole portion 42 is exposed to the front surface side of the sound absorbing panel 30 as shown in FIG. 3B, the hole portion 40 from the front surface side becomes difficult to see and a suitable appearance can be obtained. preferable. In addition, there is an advantage that dust and the like can be reduced from entering the air layer portion between the sound absorbing panel 30 and the rigid wall 20 through the holes 40.
[0033]
Further, the fine hole 42 is not limited to a shallow hole shape having a constant cross section as shown in FIG. 3, and the bottom of the large hole 41 (the tip of the hole) is tapered as shown in FIG. The portion that penetrates to the back side of the sound absorbing panel 30 is used as a fine hole portion 42, or the fine hole portion 42 is deeper than the large hole portion 41 as shown in FIG. Good.
[0034]
Furthermore, without making the hole cross section of the large hole portion 41 constant in the depth direction, the large hole portion 41 is formed in a tapered shape from one surface of the sound absorbing panel 30 as shown in FIG. As shown in FIG. 5B, the large hole portion 41 is configured in a trumpet shape in which the longitudinal section changes in a curved manner, or from both surfaces of the sound absorbing panel 30 as shown in FIG. You may form in a taper shape.
[0035]
Further, both the large hole portion 41 and the fine hole portion 42 may have non-circular cross sections. Further, a plurality of fine hole portions 42 may be provided in one large hole portion 41.
[0036]
In the hole 40 that can be formed in various shapes as described above, the equivalent diameter of the hole cross section of the large hole part 41 is 1.5 times or more and 15 times or less than the equivalent diameter of the hole cross section of the fine hole part 42. Is desirable. The lower limit side is further preferably 3 times or more, and particularly preferably 4 times or more. The upper limit side is further preferably 10 times or less, and particularly preferably 6 times or less.
[0037]
Further, it is desirable that the size of the fine hole portion 42 is such that the equivalent diameter of the hole cross section is 1 mm or less.
[0038]
The size of the large hole portion 41 is preferably such that the equivalent diameter of the hole cross section is 3 mm or more and 15 mm or less.
[0039]
Further, the depth (length) of the large hole portion 41 is desirably 0.2 times or more and 50 times or less with respect to the equivalent diameter of the hole cross section of the fine hole portion 42. The upper limit side is further preferably 15 times or less, and particularly preferably 10 times or less.
[0040]
The pitch of the hole portions 40 is desirably 2.5 times or more and 30 times or less with respect to the equivalent diameter of the hole cross section of the fine hole portion 42.
[0041]
Next, the sound absorption characteristics of the sound absorbing panel 30 and the sound absorbing device 10 will be described based on experiments performed by setting the holes 40 of various sizes.
[0042]
FIG. 6 is an explanatory diagram of the sound absorbing device 10 used in the following series of experiments. As shown in FIG. 6, in this experiment, the large hole panels 311, 312, 313 in which the large hole part 41 having the diameter D is formed, and the fine hole in which the fine hole part 42 having the diameter d and the depth t is formed. The sound absorbing panel 30 in which the depth T1 of the large hole portion 41 on the front side and the depth T2 of the large hole portion 41 on the back side can be arbitrarily set by overlapping the panel 32 as appropriate. The hole pitch p of each panel 311 ..., 32 to be overlapped is the same.
[0043]
In each experiment, such a sound absorbing panel 30 is arranged on the front surface of the rigid wall 20 via a predetermined gap (air layer thickness) L, and an acoustic impedance tube (Model 4206 manufactured by Bruel & Kjar) is used according to the measurement standard ASTME1050. The normal incident sound absorption coefficient was measured.
[0044]
FIG. 7 is an experimental result graph showing the sound absorbing effect when the large hole portions 41 having various depths are provided only on the front side of the sound absorbing panel 30. Specifically, the depth of the large hole portion 41 was set to 1 mm, 2 mm, 4 mm, 5 mm, 8 mm, 10 mm, 13 mm, and 16 mm. As other conditions, the diameter of the fine hole portion 42 is 0.555 mm, the depth of the fine hole portion 42 is 0.255 mm, the diameter of the large hole portion 41 is 2.595 mm, the pitch of the hole portions 40 is 12 mm, air The thickness of the layer was set to 160 mm, and the material of the sound absorbing panel 30 was set in common with an aluminum plate (specific gravity 2.7).
[0045]
In the following graphs, the depth of the large hole portion 41 provided on the front side of the sound absorbing panel 30 is represented by “+”, and the depth of the large hole portion 41 provided on the back side is represented by “−”.
[0046]
As shown in FIG. 7, it is recognized that the sound absorption peak center wavelength decreases to 190 Hz, 163 Hz, 138 Hz, 124 Hz, 117 Hz, and 111 Hz as the depth of the large hole portion 41 is increased to 1 mm, 2 mm,. . When the depth of the large hole portion 41 was 16 mm, it was out of the measurable range of the measuring instrument.
[0047]
From this result, it can be seen that by forming the large hole portion 41 deeply, a material having excellent sound absorbing performance in a lower frequency region can be obtained.
[0048]
FIG. 14 shows the result of theoretical calculation of the sound absorption coefficient of the sound absorbing panel provided with the same large hole portion 41 and minute hole portion 42 as in the experiment shown in FIG. This theoretical calculation assumes that the large hole portion 41 and the minute hole portion 42 are connected in series with straight pipes having different diameters, and assumes that the pipe end correction depends only on the diameter of the smallest diameter portion. As the calculation method of the tube, the method of Maa's paper presented in the above prior art (Non-Patent Document 2) was adopted.
[0049]
In FIG. 14 which is the theoretical calculation result, when compared with FIG. 7 which is the experimental result, the decrease in the peak value of the sound absorption coefficient when the large hole portion 41 becomes deep is extremely small, and the decrease in the sound absorption peak center wavelength is also small. Almost not recognized. Therefore, it is surmised that the excellent sound absorbing performance of the sound absorbing device according to the present invention has been obtained by a mechanism that is theoretically unclear in the above paper.
[0050]
As described above, in the present invention, the sound absorption performance can be improved by moving the resonance frequency to a low band by the additional mass of the large hole portion and broadening the resonance characteristics. On the other hand, in the conventional resonance type sound absorbing device, in general, in order to shift the sound absorption peak frequency to the low frequency band, it is necessary to significantly increase the thickness of the air layer. However, the fact that the sound absorption peak frequency shifts to the lower frequency side by about two-thirds of the octave from the theoretical calculation value at the same air layer thickness as in the present invention. It clearly shows that it has excellent performance in sound absorption in the low frequency region.
[0051]
FIG. 8 is an experimental result graph showing the sound absorption effect when the large hole portion 41 having a depth of 1 mm is provided on the front side of the sound absorbing panel 30 and the large hole portion 41 having various depths is provided on the back side. is there. Specifically, the depth of the large hole portion 41 on the back side was set to 1 mm, 4 mm, 6 mm, 8 mm, and 9 mm. Other conditions are the same as in the experiment of FIG.
[0052]
As shown in FIG. 8, it is recognized that the sound absorption peak center wavelength shifts to the bass side as the depth of the large hole portion 41 provided on the back side is increased to 1 mm, 4 mm,.
[0053]
Further, when the large hole portion 41 having a depth of 1 mm on the front side and 9 mm on the back side is provided, peaks of the sound absorption coefficient are recognized at two locations of 125 Hz and 250 Hz.
[0054]
FIG. 9 is an experimental result graph showing a sound absorbing effect when a relatively deep large hole is provided on the front side and the back side of the sound absorbing panel 30.
[0055]
Specifically, the results are shown when a large hole portion having a depth of 5 mm and 4 mm, a large hole portion having a depth of 5 mm and 6 mm, and a large hole portion having a size of 3 mm and 8 mm are provided on the front side and the back side, respectively.
[0056]
FIG. 10 is a graph of the experimental results of FIGS. 7 and 8 described above, in which the total depths of the large holes on the front side and the back side of the sound absorbing panel 30 are the same. Specifically, a case where a 2 mm large hole portion was provided on the front side and a case where a 1 mm large hole portion was provided on the front side and a 1 mm large hole portion on the back side were simultaneously displayed in a graph. In addition, the case where a large hole portion of 5 mm was provided on the front side and the case where a large hole portion of 1 mm was provided on the front side and 4 mm on the back side were simultaneously displayed in a graph. In addition, the case where a large hole portion of 10 mm was provided on the front side and the case where a large hole portion of 1 mm was provided on the front side and 9 mm on the back side were simultaneously displayed in a graph.
[0057]
As shown in FIG. 10, when the total depth of the large hole portion 41 is the same, it can be seen that the sound absorption coefficient distribution is substantially the same.
[0058]
FIG. 11 is an experimental result graph showing the sound absorbing effect when the large hole portions 41 having various depths are provided only on the back side of the sound absorbing panel 30. The depth of the large hole portion 41 was set to 1 mm, 2 mm, 4 mm, 8 mm, 10 mm, 13 mm, and 16 mm. As other conditions, the diameter of the fine hole portion 42 is 0.645 mm, the depth of the fine hole portion 42 is 0.295 mm, the diameter of the large hole portion 41 is 2.48 mm, the pitch of the hole portions 40 is 15 mm, air The thickness of the layer was set to 160 mm, and the material of the sound absorbing panel 30 was set in common with an aluminum plate (specific gravity 2.7).
[0059]
As shown in FIG. 11, it is recognized that the sound absorption peak center wavelength decreases to 184 Hz, 162 Hz, and 131 Hz as the depth of the large hole portion 41 is increased to 1 mm, 2 mm, and so on. When the depth of the large hole portion 41 was 8 mm, it was out of the measurable range of the measuring instrument.
[0060]
From this result, even when the large hole portion 41 is provided only on the back surface side of the sound absorbing panel 30, the sound absorption performance in a lower frequency region can be obtained by forming the large hole portion 41 deeply. You can see that
[0061]
FIG. 12 is an experimental result graph showing the sound absorbing effect when the large hole portions 41 having various depths are provided only on the front side of the sound absorbing panel 30. In this experiment, the sound absorbing panel 30 having the same fine hole as in FIG. 11 was used, and the thickness of the air layer between the rigid wall 20 and the sound absorbing panel 30 was set to 90 mm. The depth of the large hole portion 41 was set to 1 mm, 8 mm, and 16 mm.
[0062]
As shown in FIG. 12, it can be seen that the sound absorption peak center frequency decreases to 257 Hz, 158 Hz, and 155 Hz as the depth of the large hole portion 41 increases to 1 mm, 8 mm, and 16 mm.
[0063]
Next, the sound absorbing characteristics of the sound absorbing panel 30 and the sound absorbing device 10 in which the shape of the hole 40 (large hole) is tapered will be described based on experiments.
[0064]
In this experiment, the sound absorbing panel 30 having the holes 40... Having the shape shown in FIG. Specifically, the size of each part of the hole 40 is such that the diameter of the large hole 41 on the opening side is 1.73 mm, the depth of the large hole 41 is 0.52 mm, the diameter of the minute hole 42 is 0.58 mm, and minute. The depth of the holes 42 is 0.69 mm, the pitch of the holes 40 is 12 mm, the thickness of the air layer is 160 mm, and the sound absorbing panel 30 is made of an aluminum plate (specific gravity 2.7).
[0065]
FIG. 13 is an experimental result graph showing the sound absorption effect when the sound absorbing panel 30 is directed toward the front side and the large hole portion 41 toward the front side.
[0066]
As shown in FIG. 13, even in the case of the tapered large hole portion 41, there is a peak of sound absorption in the low frequency region, and an excellent sound absorption performance in the low frequency region is obtained. I understand.
[0067]
Moreover, it turns out that the sound absorption characteristic without an essential difference is acquired even if it directs the large hole part 41 toward the front side, and the back side.
[0068]
【The invention's effect】
As described above, according to the sound absorbing panel and the sound absorbing device according to the present invention, a large number of holes provided in the sound absorbing panel have a hole cross-section narrowed at least partially in the plate thickness direction of the sound absorbing panel. Since the fine hole portion is provided, it is possible to obtain the strength by securing the plate thickness of the sound absorbing panel, and it is possible to obtain excellent sound absorption performance by combining the large hole portion and the fine hole portion.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional perspective view of a sound absorbing device according to an embodiment of the present invention.
FIG. 2 is a cross-sectional explanatory view of a sound absorbing device according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view showing an example of a hole provided in the sound absorbing panel.
FIG. 4 is a cross-sectional view showing an example of a hole provided in the sound absorbing panel.
FIG. 5 is a cross-sectional view showing an example of a hole provided in the sound absorbing panel.
FIG. 6 is an explanatory diagram of a sound absorbing device used in a series of experiments.
FIG. 7 is an experimental result graph showing the sound absorption effect when large holes of various depths are provided only on the front side of the sound absorption panel.
FIG. 8 is an experimental result graph showing a sound absorbing effect when a large hole portion having a certain depth is provided on the front side of the sound absorbing panel and a large hole portion having various depths is provided on the back side.
FIG. 9 is an experimental result graph showing a sound absorbing effect when large holes of various depths are provided on the front side and the back side of the sound absorbing panel.
FIG. 10 is a graph showing a combination of the total depths of the large hole portions on the front side and the back side of the sound absorbing panel.
FIG. 11 is an experimental result graph showing a sound absorbing effect when large holes having various depths are provided only on the back side of the sound absorbing panel.
FIG. 12 is an experimental result graph showing a sound absorbing effect when large holes having various depths are provided only on the front side of the sound absorbing panel.
FIG. 13 is an experimental result graph showing a sound absorbing effect of a sound absorbing panel having a tapered large hole portion.
FIG. 14 is a graph showing the result of theoretical calculation of the sound absorption rate of a sound absorbing panel having large holes and micro holes.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Sound absorber 20 Hard wall 30 Sound absorption panel 40 Hole part 41 Large hole part 42 Fine hole part 50 Holding member (holding means)

Claims (6)

A sound-absorbing panel disposed on the front surface of the rigid wall with a predetermined interval, and provided with a large number of holes penetrating in the thickness direction of the sound-absorbing panel. A sound absorbing panel, wherein a hole is exposed, and at least a part of the plurality of holes in a plate thickness direction is provided with a fine hole having a hole cross-section narrower than the large hole. The sound absorbing panel according to claim 1, wherein the fine hole portion is provided so as to be exposed on one side of the sound absorbing panel. The sound absorbing panel according to claim 1, wherein the fine hole portion is provided so as to be exposed on a front side of the sound absorbing panel. The sound absorbing panel according to claim 1, wherein the large hole portion has a constant hole cross section up to a predetermined depth in the plate thickness direction. The equivalent diameter of the hole cross section of the large hole portion is 1.5 times or more and 15 times or less of the equivalent diameter of the hole cross section of the fine hole portion, according to any one of claims 1 to 4. Sound absorbing panel. A rigid wall,
The sound absorbing panel according to any one of claims 1 to 5,
Holding means for holding the sound absorbing panel on the front surface of the rigid wall at a predetermined interval;
A sound absorbing device comprising:

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