JPH07300821A - Sound absorber - Google Patents

Abstract

PURPOSE:To provide a sound absorber which is excellent in durability being inexpensive and capable of effectively reducing noise and especially traffic noise, such as railway and roads. CONSTITUTION:In a sound absorbing product which comprises a binder and an aggregate, there is formed a layer which uses large-sized particles as an aggregate on a sound absorbing side surface while there is formed a layer which uses small-sized particles as the aggregate adjacent to the above layer. The diameter of large particles ranges from 1 to 200mm while the diameter of small-sized particles ranges from 0.5 to 5.0mm. The ratio between the diameter of the large-sized particles and that of the small-sized particles should be preferably from 0.01 to 0.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing body, and more particularly to a sound absorbing body for reducing traffic noise mainly on railways and roads by forming a layer using an aggregate having a specific grain size.

[0002]

2. Description of the Related Art Examples of noise include traffic vibrations and noises on railways, roads, etc., as well as noises emitted from machine tools and manufacturing machines, all of which cause daily discomfort and cause stress. .

Railway noise is transmitted by sounds radiated from the vehicle such as pantograph noise, aerodynamic noise, and rolling noise, and vibrations from the vehicle.
Sound is radiated from structures such as viaducts.

To reduce the sound emitted from the vehicle, a soundproof wall is provided and a sound absorbing material such as glass wool or foamed aluminum is attached to the inside of the soundproof wall. In addition, the use of ballast and foamed concrete laid with crushed stone for the roadbed has also been used to obtain a greater sound absorbing effect.

Further, as a method of reducing road traffic noise,
It is widely practiced to install sound barriers and soundproof planting on both sides of the road, but these are mainly used around automobile roads because they require a large area around the road.
In recent years, as a noise countermeasure near a noise source, a sound absorbing pavement material having an asphalt pavement having many voids as a surface layer has been developed.

[0006]

However, the glass wool as the sound absorbing material is inferior in durability such as scattering when exposed to wind and rain, and the metal porous body such as foamed aluminum is expensive as a material. There is a drawback that. The method of obtaining vibration insulation and sound absorbing effect by ballast is 30c in order to obtain sufficient sound absorbing performance because the diameter of the crushed stone is large.
There is a drawback that the thickness is required to be about m and the weight becomes very large. In addition, since the crushed stone is not fixed with a binder, etc., there is a drawback that the voids gradually become clogged with wind and rain or vibration from the train over time, and the sound absorbing performance deteriorates. Therefore, there are problems such as durability and complexity of maintenance.
Further, although foamable concrete has a porosity of about 90% and exhibits good sound absorption, it has insufficient porosity because of its large porosity, and when it is used for a roadbed, etc., it needs to be reinforced with expanded metal or the like. Yes, it became expensive.
Further, since the size of each void is small, rainwater or the like stays inside and is damaged when frozen, which is not suitable for use in cold regions.

The sound absorbing pavement material used for reducing road traffic noise is mainly intended for drainage, and has good strength and weather resistance, but its sound absorbing effect is not sufficient.

The object of the present invention is to be inexpensive, excellent in durability,
Moreover, it is another object of the present invention to provide a sound absorber capable of effectively reducing noise, particularly traffic noise of railways and roads.

[0009]

The sound absorbing body according to claim 1 of the present invention is a sound absorbing body comprising a binder and an aggregate, wherein a layer using particles having a large particle size is formed as the aggregate on the sound absorbing surface side. Then, a layer using particles having a small particle size as an aggregate is formed adjacent to the layer.

A second aspect of the present invention is the sound absorbing body according to the first aspect, wherein the aggregate is crushed stone, sand or rubber particles.

[0011]

The propagation of sound in the sound absorber will be described with reference to FIG. Part of the incident sound wave is reflected on the surface and the rest is transmitted inside. The transmitted sound wave attenuates while traveling inside, is reflected by the bottom surface, and is re-emitted from the surface. Therefore, a sound absorber having less reflection on the surface and large attenuation of sound waves inside is preferable as the sound absorber. In the present invention, since the layer is formed using particles having a large particle size as the aggregate on the sound absorbing surface side, sound waves reflected on the sound absorbing side of the surface are reduced,
The sound waves are effectively transmitted to the inside of the sound absorbing body. Also,
Since a layer using particles having a small particle size is formed as an aggregate adjacent to the layer, sound waves are effectively attenuated in the particle layer having a small particle size. Therefore, the sound absorbing body of the present invention is useful for noise reduction. Further, by using rubber particles as the aggregate, noise is effectively reduced due to the elasticity of the rubber particles and the effect of individual voids existing around the rubber particles. In addition, since aggregates such as rubber particles and binders are generally used for pavements, etc.,
A sound absorber that is inexpensive and has excellent durability even when used for transportation can be obtained.

[0012]

The present invention will be described in detail below with reference to specific examples.

According to the present invention, in a sound absorbing body composed of a binder and an aggregate, a layer using particles having a large particle size as the aggregate is formed on the sound absorbing surface side, and a layer having a particle size of the aggregate is formed adjacent to the layer. It is characterized by forming a layer using small particles.

Particles having a large particle size (hereinafter referred to as large particles) used as an aggregate in the present invention mean particle sizes of 1 to 2
It refers to the one with 00 mm. The particles do not necessarily have to be spherical, and may have an elliptical shape, a tabular shape, or an irregular shape. These particle diameters are projection views of a portion having the maximum particle diameter. Shall be represented by the longest diameter of. The particle size is arbitrary within the above range, but is preferably 3 to 50 mm, more preferably 5 to 10 mm from the viewpoint of smoothness of the surface and securing of voids. Specific examples of the particles used for the large-diameter particles include crushed stone, gravel, rubber particles, sand, synthetic resin particles, and steel slag, but rubber particles are preferable from the viewpoint of adhesion with the binder. As the rubber particles, other than rubber particles molded by a conventional method, powdered rubber, spews generated during tire vulcanization,
It is possible to use crushed products of used tires, grinding scraps of tire tread generated during the production of recycled tires, and crushed products of used rubber products such as rubber belts and anti-vibration rubbers. As described above, the rubber particles do not necessarily have to be spherical, and the shape is arbitrary. As the synthetic resin particles, in addition to synthetic resin particles molded by a conventional method, fiber reinforced plastic (FRP), crushed material of general-purpose resin product waste, and the like can be used. In addition, specific examples of the other large-sized particles include, for example, natural aggregates made of natural stone such as river gravel and river sand, and artificial aggregates made of slag, crushed stone, etc., but are not particularly limited. No. 5 (particle size range 20 to 13 mm), No. 6 (13 to 5 mm), No. 7 (5 to 2.5 mm) or equivalent size river gravel, gravel,
Examples include natural aggregate such as river sand and sea sand. Further, in addition to these crushed stones and gravel, hard ones such as steel slag can be arbitrarily used as long as the particle size is within the preferable range.

The thickness of the layer formed of large-diameter particles as the aggregate formed on the sound absorbing surface side of the sound absorbing body is preferably about 10 to 50 mm, though it depends on the purpose of use of the sound absorbing body. The sound reflection on the surface of the sound absorbing body is minimized, and there is no fear of impairing the sound absorbing effect.

In the present invention, the particles having a small particle size (hereinafter referred to as small particles) used as the aggregate have a particle size of 0.5.
Refers to those of ~ 5 mm. The fact that the particles do not necessarily have to be spherical is the same as described for the large-diameter particles.
Further, the particle size is defined similarly to the large particle. The particle size is arbitrary within the above range, but the particle size of the small particle used is preferably about 0.01 to 0.5 of the particle size of the large particle used in combination. Specific examples of particles used for the small particles include, for example, crushed stone, gravel, rubber particles,
Examples include sand, synthetic resin particles, steel slag, and the like. As the rubber particles, in addition to the rubber particles molded by the usual method, pulverized products of used rubber products and the like can be used. As the synthetic resin particles, other than the synthetic resin particles molded by the usual method, F
It is also possible to use a crushed material of a waste resin product such as RP. Specific examples of the other small-sized particles include, for example, natural aggregates made of natural stone such as river gravel and river sand, and artificial aggregates made of slag, crushed stone, etc., but are not particularly limited; Crushed stone No. 7 (5 to 2.5 mm), silica sand No. 4 (0.3 to 0.6 mm), No. 5 (0.15 to 0.
3 mm) or an equivalent size of natural aggregate such as river gravel, mountain gravel, river sand, and sea sand. Further, in addition to these crushed stones and gravel, hard ones such as steel slag can be arbitrarily used as long as the particle size is within the preferable range.

The thickness of the layer formed of small-diameter particles as an aggregate formed adjacent to the large-diameter particle layer of the sound absorber is preferably about 30 to 300 mm, although it depends on the purpose of use of the sound absorber. If so, an effective sound absorption coefficient due to the small-diameter particle layer can be obtained.

As the binder of the sound absorbing body, asphalt is generally used, and other binders are, for example, one-component type or two-component type epoxy type, urethane type,
Acrylic-based and saturated or unsaturated polyester-based polymer resins, acrylic-based, vinyl acetate-based, urethane-based,
Examples include rubber-based polymer resin emulsion-based or organic solvent-based adhesives, and these polymer resins may be used, or these may be mixed with asphalt in consideration of durability and the like. In addition, rubber such as SBR (styrene-butadiene rubber), CR (chloroprene rubber) or EVA (ethylene-vinyl acetate copolymer), SBS (styrene-butadiene-styrene block copolymer) or the like in asphalt. A modified asphalt to which a simple substance or a mixture of the polymer particles is added as a modifier can be used for improving durability.

By mixing the aggregate and the binder, the aggregate partially adheres to each other via the binder, and the voids are retained after the binder is hardened.

In the present invention, the porosity of the sound absorber is not particularly limited, but it is preferable that each layer has a porosity of 15 to 40%. When the porosity is in this range, the damping rate of vibration and sound waves in the sound absorbing body is sufficient, and sufficient durability can be obtained by selecting appropriate particles and binder.
In the present invention, the porosity is represented by the following formula.

1- (apparent density / theoretical density) [where the apparent density is (total weight / apparent volume),
The theoretical density is obtained from (total weight of raw material mixture / total volume of mixture obtained from the density of each mixture). The content of the sound absorber is preferably 2 to 15 parts by weight with respect to 100 parts by weight of the aggregate, and a desired porosity can be obtained by adjusting the ratio of the binder to the aggregate. .

As an example of the method for producing the sound absorbing body, small-sized particles are kneaded by a mixer for several minutes to homogenize them, and a binder is added and mixed to form a mixture of the small-sized particles and the binder, which is then put into a molding die. Then, the binder is cured, and then a mixture of the large-diameter particles and the binder obtained in the same manner is added onto the small-diameter particle layer to form a plate shape. When asphalt is used as the binder, the asphalt mixture may be either a heated mixture used by heating asphalt or a room temperature mixture used as liquid asphalt at room temperature. When the sound absorber of the present invention is used as a road or railroad bed,
First, the mixture of small particles and binder such as asphalt is put on the base layer of the road or road bed to be the base, and the mixture is hardened, and then the mixture of large particles and binder such as asphalt is put and tightened. It can be hardened and laid directly. In any case, sufficient strength for walking on the surface can be obtained, so that a reinforcing material such as expanded metal is not required, and an inexpensive sound absorbing body having good sound absorbing characteristics can be obtained.

Further, as the sound absorbing body of the present invention, a rubber-like substance is used as a binder and molded into a sheet-shaped rubber composition, so that it can be installed at a desired place by means such as adhesion or screwing. A sound absorber can be obtained.

FIG. 2 is a graph showing the reflectance of sound waves on the surface of the sound absorber when the particle size is changed. As is clear from FIG. 2, the reflectance decreases as the particle size increases, and the reflection on the surface becomes 50% or less when the particle size exceeds 3 mm. FIG. 3 is a graph showing attenuation of sound waves of the sound absorber when the particle size is changed. As is clear from FIG. 3, the smaller the particle size, the larger the internal attenuation. The particles used for these measurements had a uniform particle size. Generally, crushed stone and the like are classified by a sieve, and therefore, the particle size has a distribution of the size of the mesh of the sieve. However, the more uniform the particle size distribution, the larger the porosity and the better the sound absorbing performance, which is preferable.

The two-speaker method [Utsuno et al.
Proceedings of the Acoustical Society of Japan (March, 1990) No. 519-5
P. 20 (1990)].

Example 1 Crushed stone having a grain size of 9.5 to 6.7 mm was used as the aggregate on the sound absorbing surface side, and coarse sand having a grain size of 1.7 to 1.0 mm was used as the aggregate in the adjacent layer. A sound absorber was created using. The large-diameter particle layer had a thickness of 20 mm, the small-diameter particle layer had a thickness of 70 mm, and was molded using 3 wt% of a two-component epoxy resin as a binder to obtain a product of the present invention. Further, a sound absorbing body having a thickness of 90 mm was prepared by using coarse sand having a particle size of 1.7 to 1.0 mm and 3% by weight of a two-pack type epoxy resin, and used as a comparative product. The normal incident sound absorption coefficient of each sample was measured. The measurement result of the sound absorption coefficient is shown in FIG.

FIG. 4 is a graph showing the relationship between the frequency of the sound waves of the sound absorbing body of the present invention product and the comparative product and the normal incidence sound absorption coefficient.

The horizontal axis represents the frequency of sound waves, and the vertical axis represents the normal incident sound absorption coefficient. As is clear from FIG. 4, it is clear that the product of the present invention exhibits a good normal incidence sound absorption coefficient and has excellent sound absorption performance. On the other hand, the comparative product has a single layer structure despite using the same aggregate as that used for the lower layer of the present invention, and therefore has a poor sound absorption coefficient as compared with the inventive product and has a sound absorbing performance. Turned out to be inadequate.

As a method of using the sound absorbing body of the present invention, when a sound absorbing body having a desired composition, thickness and porosity required by a noise source is prepared and used as a measure against railroad noise, for example, on a concrete roadbed. By laying it in, it absorbs sound. When used as a measure against road traffic noise, for example, the sound absorber of the present invention is attached to the surface layer of the pavement or is laid directly on the base layer of the pavement to be used to effectively emit the sound emitted from the automobile. It absorbs sound and reduces noise.

As described above, the sound absorbing body of the present invention can suitably use recycled rubber products such as used tires, crushed FRP waste materials, and recycled resources such as steel slag, so that the sound absorbing body can be manufactured at low cost. Not only can it be realized, but it also has favorable advantages in terms of environmental protection and resource saving.

[0031]

EFFECTS OF THE INVENTION Since the sound absorbing body of the present invention has the above-mentioned structure, it has an excellent effect that it is inexpensive, has excellent durability, and reduces noise caused by traffic or the like.

[Brief description of drawings]

FIG. 1 is a model cross-sectional view showing a state of sound propagation in a sound absorbing body of the present invention.

FIG. 2 is a graph showing the reflectance of sound waves on the surface of the sound absorber when the particle size is changed.

FIG. 3 is a graph showing attenuation of sound waves in the sound absorbing body when the particle size is changed.

FIG. 4 is a graph showing the relationship between the frequency of sound waves and the normal incidence sound absorption coefficient of the sound absorbers of the present invention product and the comparative product.

Claims (2)

[Claims] 1. A sound absorbing body comprising a binder and an aggregate, wherein a layer using particles having a large particle size is formed as an aggregate on the sound absorbing surface side, and a particle having a small particle size is formed as an aggregate adjacent to the layer. A sound absorbing body characterized by forming a layer using. 2. The sound absorber according to claim 1, wherein the aggregate is crushed stone, sand or rubber particles.