JP2000144968A - Sound absorption material and sound absorption panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sound absorption and obtain at least the same sound absorption characteristic as the conventional product even when it is lightweight by providing unevenness on at least one face of a plate-like sound absorption material, bringing it into contact with the neighborhood of the top of a crest making the projection part of the sound absorption material, and stretching a resin film so as to be separated from a trough making a recess part. SOLUTION: A sound absorption material comprising plate-like glass wool, rock wool or the like is provided with a shape having crests and troughs on at least one face of its surface, brought into contact with the neighborhood of the top of the crest making projection parts of its surface, and the resin film 4 of a fluororesin film or the like is stretched so as to be separated from the troughs making recess parts. The sound absorption material 1 is housed in a box body, a protection material is arranged on the front face of the sound absorption material 1 at need, and a through hole metal plate is arranged on the sound absorption face. The box body and the through hole metal plate are fixed by a press frame material to form an outer frame material so as to constitute a sound absorption panel. Thereby a propagating sound wave reaches the surface of the sound absorption material 1 through the hole of the through hole metal plate to produce sound absorption effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing material and a sound absorbing panel having remarkably improved sound absorbing performance.

[0002]

2. Description of the Related Art In general, in a two-layer structure having a road or a track under an elevated road such as an expressway, noise generated from vehicles traveling on the lower road is reflected on the back of the upper elevated road, and the noise level in the surrounding area is increased. Is rising, which is problematic. As a countermeasure against this, there is known a technique of lowering the noise level by installing an elevated backside sound absorbing plate on the underside of the elevated side as disclosed in Japanese Patent Application Laid-Open No. 9-158115.

FIG. 6 is a cross-sectional view showing an example of a conventional sound absorbing panel installed on the backside of an elevated building. The plate-shaped sound absorbing material 1 uses a cotton-like material such as glass wool or a porous board, and is covered with a fluororesin film 4 or the like for waterproofing and preventing deterioration due to ultraviolet rays. Such a sound absorbing material is weak as a material, and has such a property that it is deformed by its own weight in a state where the sound absorbing material is attached alone to the underside of the elevated structure, or is easily damaged by wind, rain, flying objects, and the like. Therefore, the sound absorbing panel is usually used in the state of a sound absorbing panel in which such a sound absorbing material is housed in the outer frame material 9. In this sound absorbing panel, the sound absorbing material is housed in a rigid box 7 and the sound absorbing material 1 has a sound absorbing surface side (lower surface side).
Is supported by a perforated metal plate 6 or the like and fixed by a holding frame material 8. Usually, between the sound absorbing material 1 and the perforated metal plate 6,
In many cases, a resin film covering the sound absorbing material is protected by interposing a protective material 5 such as a glass cloth subjected to a water treatment.

[0004] Noise generated from below the elevated road enters the sound absorbing material 1 through the perforated metal plate 6 of the sound absorbing panel, where its energy is attenuated and reflected. Therefore,
It is possible to reduce noise propagation to the surrounding area due to acoustic reflection on the backside of the elevated road.

[0005]

It is, of course, necessary for such an elevated backside sound-absorbing material to have a sufficient sound absorbing effect. It is preferable to be lightweight from the viewpoint of reducing the load on the pillars and beams, or the ease of construction. An object of the present invention is to improve the sound absorbing effect by renewing the shape and configuration of the sound absorbing material, and to provide a sound absorbing material and a sound absorbing panel which have the same or higher sound absorbing characteristics as conventional products even if they are lightweight. As an issue.

[0006]

As a result of pursuing a technique for improving the sound absorbing performance of the sound absorbing panel and reducing the overall weight when the sound absorbing panel is configured as a sound absorbing panel, the following is achieved without changing the material of the sound absorbing material. It has been found that the sound absorbing effect can be improved by using the shape and configuration of the sound absorbing material.
In addition, by using this to form a sound absorbing panel, a sound absorbing panel that is lightweight and can reduce construction work could be manufactured. The technical means are as follows.

(1) A resin is provided such that irregularities are provided on at least one surface of a plate-shaped sound absorbing material, and the sound absorbing material is in contact with an apex of a peak forming a convex portion on the uneven surface side, and is separated from a valley forming a concave portion. A sound absorbing material characterized by being stretched with a film.

(2) A sound absorbing panel in which the sound absorbing material is housed in an outer frame material, the outer frame material having rigidity and at least one surface of the sound absorbing material housed in the outer frame material. A sound-absorbing panel comprising an outer frame member having a perforated metal plate disposed on an uneven surface side.

The uneven surface of the sound absorbing material has a pitch between peaks of 20 to 200 mm and a height difference between peaks and valleys of 10 to 50 m.
By setting m, it is particularly suitable for reducing the weight, which is the subject of the present invention, and improving the sound absorption characteristics.

[0010] As the material of the plate-like sound absorbing material in the present invention, cotton-like materials such as glass wool, rock wool, and porous board which are used as ordinary sound absorbing materials can be used. By providing irregularities on the surface of the plate-shaped sound absorbing material and covering the surface with a resin film, the sound absorbing effect can be improved. It is necessary that the resin film is in contact with the surface of the plate-shaped sound absorbing material near the apex of the peak, and that a space is opened between the film and the plate-shaped sound absorbing material at the valley.

When the resin film is stretched in this way, the resin film vibrates freely when a sound wave is applied, and the vibration converts the sound energy into heat energy, so that the reflected sound energy can be reduced. It is.

It is necessary to stretch the resin film on the uneven surface of the sound absorbing material in a tensioned state. In this case, since the contact is substantially made at the surface near the peak of the peak, if the pitch between the peaks is less than 20 mm, the gap between the sound absorbing material and the resin film at the valley portion is substantially almost zero. May disappear. Also, if the pitch is wider than 200 mm, if the resin film becomes loose, the film and the sound-absorbing material may still be in contact with each other and the gap may disappear, so the pitch between the peaks is between 20 and 200 mm. It is necessary.

When the height difference between the peak and the valley is less than 10 mm, the contact between the film at the peak position and the surface near the peak is also large, so that the gap between the sound absorbing material and the resin film at the valley portion is substantially reduced. Is not preferred because it may almost disappear. If the height difference exceeds 50 mm, the thickness of the sound-absorbing material is substantially increased, and when the sound-absorbing panel or the like including the sound-absorbing material is formed, the thickness of the panel cannot be reduced, thereby reducing the overall weight. Less is.
As the resin film, vinyl resin, polyethylene, polyester, silicon resin, and the like that vibrate by sound waves as described above can all be used, but in particular, a fluororesin film is excellent in strength and moisture resistance, and can be preferably used. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a sound absorbing material 1 of the present invention has a shape having peaks 2 and valleys 3 on at least one surface, and a resin film 4 is stretched on the surface.
FIG. 2 shows a cross section of a sound absorbing panel using this sound absorbing material. Since the sound absorbing material 1 is housed in a box 7 and a perforated metal plate 6 is arranged on the sound absorbing surface, the transmitted sound wave Reaches the surface of the sound absorbing material through the holes of the perforated metal plate, and a sound absorbing effect is produced. If necessary, a protective material 5 may be provided in front of the sound absorbing surface of the sound absorbing material. By arranging the protective material 5, it is possible to prevent the resin film on the sound absorbing surface side of the sound absorbing material from being damaged by flying objects and from being deteriorated due to rainwater adhesion. The box 7 and the perforated metal plate 6 are fixed by the holding frame member 8 to form the outer frame member 9. Sound absorbing material 1
Is stored in the outer frame member 9 to form a sound absorbing panel.

The unevenness of the sound absorbing material 1 may be any shape as long as a gap is formed between the resin film 4 and the valley 3 of the sound absorbing material 1 when the resin film 4 is stretched on the surface, as shown in FIG. Various shapes can be adopted. That is, the shape of the peaks and valleys is round as shown in FIG. 3 (a), the shape of a pyramid as shown in FIG. 3 (b), the shape in which the bowl shown in FIG. FIG. 3 (d) is a shape in which the bowls are arranged upward.
As shown in (e), the sound absorbing material may have irregularities on both surfaces. The unevenness may be formed in a groove shape in one direction of a plane, or a peak or a valley having unevenness in a biaxial direction may be formed in a spot shape.

The sound absorbing panel containing the sound absorbing material has a structure in which the surface of the sound absorbing material is directed to the sound absorbing surface side. In the case of the sound absorbing material having unevenness on both surfaces, whichever is disposed on the sound absorbing side and used. You may. As the perforated metal plate 6, a metal plate such as stainless steel or aluminum having an opening such as lath metal, punching metal, and gold steel can be used. Particularly, it is desirable to use stainless steel from the viewpoint of weather resistance.

According to the present invention, the sound absorbing performance of the elevated rear sound absorbing plate can be improved.

[0018]

EXAMPLES In order to evaluate the performance of the sound absorbing material of the present invention, the oblique incidence sound absorbing coefficient was measured. The oblique incidence sound absorption coefficient measurement was performed in accordance with the sound absorption performance test method specified in the 1995 call for proposals for the Building Technology Evaluation System “Development of a sound absorbing plate with a large noise reduction effect”. The materials and compositions shown in Table 1 were used as test specimens, and the oblique incidence sound absorption coefficients of the sound absorbing materials of the examples and comparative examples were measured. The configuration of this test body is the same as the configuration when the sound absorbing material is used as an elevated back surface sound absorbing panel, in which a fluororesin film is stretched over the sound absorbing material, and a protective material and a metal lath are placed. The unevenness of the sound absorbing surface is as shown in FIG.

[0019]

[Table 1]

The oblique incidence sound absorption coefficient was measured as follows. In a semi-anechoic room having a floor of 7 m × 8 m and a height of 6 m, a test body 11 of 20 m ² or more was installed on the floor (rigid wall surface) 10. As shown in FIG. 4, the arrangement of the test body 11, the speaker 12 as a sound source, and the microphone 13 were such that the distance H between the speaker 12 and the wall was 3 m and the distance h between the microphone and the rigid wall was 2.5 m as shown in FIG. In the case where the incident angle is θ (degree) other than 0 degree, as shown in FIG.
The speaker 12 and the microphone 13 were installed at a position having an angle of θ from the vertical line on a circumference having a radius R of 3 m centered on one point on the surface of the test specimen 11 in a plane perpendicular to the plane 1 . The test sound used in the signal compression method (T
The measurement frequency range was a 1/3 octave band of 400 to 4000 Hz. As the microphone 13, a precision sound level meter type 1/2 microphone was used.

As a result of the test, the sound absorbing material of the present invention has an average oblique incidence sound absorbing coefficient of 0.93, which is comparable to 0.92 of the conventional sound absorbing material as a comparative example. Achieved the acceptance criteria for sound absorption performance. Therefore, the same sound absorbing effect as that of the conventional product can be obtained with the sound absorbing material having a thickness of 100 mm at the maximum, and the weight of the sound absorbing panel can be reduced to about 80% of the conventional product.

The method for obtaining the oblique incidence sound absorption coefficient α (θ) is as follows.

Before and after installation of the test body, reflected sound components observed at the same measurement position are extracted from each waveform. Let Pr (f) be the power spectrum of the reflected sound obtained under the hard wall condition of the incident angle θ, and Ps (f) be the power spectrum of the reflected sound obtained under the test object installation condition. Here, the sound absorption coefficient of the specimen with respect to the incident angle θ is defined by the following equation according to the energy ratio of sound lost before and after the specimen is set.

Α (θ) = 1−Ps (f) / Pr (f) α (θ): oblique incidence sound absorption coefficient θ: incident angle of sound Pr (f): power spectrum of reflected sound obtained under hard wall condition Ps (f): Power spectrum of the reflected sound obtained under the installation condition of the test specimen The calculation method of the average oblique incidence sound absorption coefficient α _{R, A} is as follows.

The average spectrum proposed by the Acoustical Society of Japan as the frequency characteristics of road traffic noise (Tachibana et al., “Energy-Based Road Noise Prediction Method,” Journal of the Acoustical Society of Japan, vol.
No. (1994)), the average oblique incidence sound absorption coefficient was calculated using the value obtained by correcting the A characteristic and the measurement result of the oblique incidence sound absorption coefficient of each specimen. Table 2 shows the calculation method.

Oblique incidence sound absorption coefficient α for road traffic noise
_{R, A} (θ) is calculated as shown in the matrix of Table 2.

[0027]

[Table 2]

Here, L _Ai : A-characteristic spectrum (dB) of road traffic noise at the ith frequency αi: Oblique incidence sound absorption coefficient at the frequency and incidence angle θ Oblique incidence sound absorption rate α _{R, A} ( θ) is the following equation.

Α _{R, A} (θ) = [Σαi · 10 ^{LAi / 10} / Σ10 ^{LAi / 10} ] The arithmetic average of the oblique incidence sound absorption coefficient α _{R, A} (θ) obtained at each angle is calculated, and the result is calculated. Is the average oblique incidence sound absorption coefficient α _{R, A.}

Α _{R, A} = [α _{R, A} (0) + α _{R, A} (π / 1
2) + α _{R, A} (π / 6) + α _{R, A} (π / 4)] / 4

[0031]

According to the present invention, since the surface of the sound absorbing material is made uneven, and a resin film in contact with the apex of the convex portion is stretched, the elevated rear sound absorbing plate using this sound absorbing material has remarkable sound absorbing performance. It became possible to improve. Further, in the case of the current sound absorbing performance standard, the thickness of the sound absorbing material can be reduced, so that the weight and cost of the sound absorbing plate can be reduced, and the sound absorbing plate can be applied to a sound absorbing plate other than the elevated rear sound absorbing plate. In addition, there is also an effect that it can be used for other organizations such as railways.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a sound absorbing material of an embodiment.

FIG. 2 is a sectional view of a sound absorbing panel using the sound absorbing material of the embodiment.

FIG. 3 is a cross-sectional view showing various uneven shapes of the sound absorbing material of the example.

FIG. 4 is an explanatory diagram of a performance test.

FIG. 5 is an explanatory diagram of a performance test.

FIG. 6 is a sectional view of the sound absorbing panel.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 sound absorbing material 2 peaks of sound absorbing material 3 valleys of sound absorbing material 4 fluororesin film 5 protective material 6 transparent metal plate 7 box body 8 holding frame material 9 outer frame material 10 rigid wall surface 11 test body 12 speaker 13 microphone

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masaki Mabuchi 2-3-2 Uchisaiwaicho, Chiyoda-ku, Tokyo F-term in Kawasaki Steel Corporation (reference) 2D001 AA05 BB01 CA01 CB05 CC02 CD03 2E001 DF03 GA17 GA18 GA23 HB02 HB03 HB04 HD11 JA22 JA25

Claims (2)

[Claims] 1. A resin film in which irregularities are provided on at least one surface of a plate-shaped sound absorbing material, the resin film is in contact with a vicinity of a peak of a peak forming a convex portion on the concave and convex surface side, and is separated from a valley forming a concave portion. A sound absorbing material characterized by being stretched. 2. The sound-absorbing panel according to claim 1, wherein the sound-absorbing material according to claim 1 is a sound-absorbing panel formed by absorbing sound with an outer frame material. A sound-absorbing panel comprising an outer frame member having a perforated metal plate disposed on at least one uneven surface side.