JPS6125160B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sound absorbing structure made of a transparent synthetic rubber thin film material, and more specifically to a transparent structure having a non-linear tensile stress-elongation curve, a high elongation rate, and a slow response to stress upon recovery. The sound-absorbing performance is enhanced by the oil-extended synthetic rubber thin film material and the resonant air layer formed behind the thin film material, resulting in an excellent soundproofing/sound-absorbing structure. Materials that are widely used as sound absorbing materials for conventional soundproofing structures due to the need to convert or block energy for soundproofing include (a) perforated plates, (b) porous materials such as glass wool and rock wool, and (c) plate-like materials. , d foam materials, etc. These materials are used alone or in combination, but none of them can be made transparent, spoiling the appearance of the soundproof structure and blocking sunlight, making the indoor environment worse. It's causing consequences. Since these sound-absorbing materials are based on a sound-absorbing mechanism that utilizes attenuation caused by the viscosity of air on the particle surface or attenuation due to the bending rigidity of the plate, it is not possible to increase the sound absorption coefficient particularly in the low frequency range. Also, although transparent plastic materials are used in some areas, these are only sound barriers that do not absorb sound. This invention was developed with the intention of providing a new sound absorbing structure. One purpose of this invention is to forcibly absorb sound energy from the outside with a high sound absorption coefficient through internal loss under the resonance effect. An object of the present invention is to provide a sound absorbing structure capable of increasing sound absorption coefficient in a low frequency range by constructing a resonant air layer using a transparent synthetic rubber thin film material having a slow stress response characteristic and a slow stress response characteristic. Another object of the present invention is to provide a sound absorbing structure that can exhibit excellent sound absorbing performance over a wide range of frequencies by combining transparent synthetic rubber thin film materials in multiple layers. The nature or objects and advantages of the invention will become apparent from the detailed description and accompanying drawings. In addition, in the drawings, the same reference numerals indicate similar reference numerals. The sound absorption mechanism of the present invention is attenuation caused by internal loss of energy in a substantial portion of the material. In other words, when sound vibration energy enters a thin film material, forced attenuation of the vibration will occur if the resonance effect forces the material to have internal loss, that is, the material has slow response characteristics, and is accompanied by a phase delay. Prevents continuation of vibration. Therefore, an additional supply of energy is required from the outside, which manifests itself in the absorption of sound. Here, the correlation between the phase delay (or advance) at each point of the plate subjected to vibration and the resonant vibration of that plate has already been reported (for example, in Japanese patent application No.
99109 specification)). A typical example of the transparent rubber thin film material described in this invention is a large block copolymer of styrene-butadiene rubber (SBR) with a molecular weight of 30 to 50%.
It is desirable that the oil-extended SBR is made by mixing process oils in an emulsified state and co-coagulating them, and that does not require vulcanization to achieve an elongation rate of 800% or more. Therefore,
JIS hardness is around 60. As shown in the experimental examples described below, such SBR can be a transparent material with a non-linear tensile stress-elongation curve, a high elongation rate, and a slow response to stress upon recovery. Therefore, not only oil-extended SBR exhibiting such characteristics, but also synthetic rubbers of diene polymers having the above characteristics or blended thin film materials with synthetic resins having these as main components can be used. This invention was realized in a soundproof structure by utilizing the characteristics of a transparent synthetic rubber thin film material, and its feature is that a transparent oil-extended synthetic rubber thin film material is used on the sound source side of the opposed frames. is stretched, and a transparent plastic tone plate is stretched on the side opposite to the sound source side, and a resonant air layer is formed between the two stretched members. Another invention is to obtain a transparent oil-extended synthetic rubber thin film material, a transparent non-oil-extended synthetic rubber with different molecular weights, a thin film material mainly composed of these, or a combination of these to obtain the optimum value between the two members. 1 thin film material
It is characterized by having a multi-layer structure in which one or more materials are stretched at regular intervals. This makes it possible to exhibit excellent sound absorption characteristics over a wide frequency range. This invention creates a resonator having a resonant air layer made of a transparent synthetic rubber thin film material, and absorbs sound energy centered on the resonant frequency. When the stiffness of the plate or membrane itself can be ignored due to the viscosity of air, the resonance frequency [ ₀ ] is determined by the following equation. However, c... Speed of sound in air ρ... Air density m... Mass per unit area d... Thickness of back air layer However, in the case of synthetic rubber thin film material

【formula】 It can be applied to

Regardless of [Formula], a coefficient is entered that increases in value of ₀ as the molecular weight and elongation increase. FIG. 1 is a curve showing the tensile stress-elongation characteristics, which is a graph of experimental data of the transparent synthetic rubber thin film material according to the present invention. The subscripts in the figure indicate SBR, which is a block copolymer that is not vulcanized. In the same figure, the growth (%) is determined by the slow response of recovery.
In order to increase the molecular weight (viscosity average molecular weight
This figure shows the tensile stress-elongation curve of oil-extended SBR with Mv) 1.7 times that of SBR and 50% process oil mixed in to improve physical properties. The curve shows that without mixing process oil.
The film thickness of the SBR material was 1 mm. Note that the diagram shows the history at 80% elongation of the elongation at break. As seen in the figure, all of them have a non-linear shape and show a high elongation rate, causing a large stress delay in recovery, but the elongation rate of the oil-extended SBR is twice that of the SBR of It has a score of over 800% and is characterized by a long recovery path. FIG. 2 is a graph showing the measurement results of the normal incidence sound absorption coefficient of each SBR material according to the explanation in FIG. 1. As can be seen in the figure, the non-oil extended SBR that does not contain process oil exhibits the same value as the general plate-like sound absorption properties, exhibiting a sound absorption coefficient of around 0.05 in each frequency range, and has almost no sound absorption effect. It shows. On the other hand, oil-extended SBR shows an excellent sound absorption coefficient of 0.75 in the high frequency range with a peak of 1600Hz. Furthermore, if an air layer is added, the peak will shift to the lower frequency side depending on the thickness of the air layer, and an excellent sound absorption coefficient can be exhibited. Figure 3 shows that even though the non-oil-extended SBR shown above, which does not contain process oil, cannot have a resonant sound absorption effect by itself, by adding an air layer, both of them can combine to produce a resonant effect due to the phase difference. This is experimental data proving that the sound absorption coefficient increases. The symbols in the figure represent the following. ′: Non-oil extended SBR with an air layer on its back side 10
Added in mm thickness. ′: non-oil-extended SBR with an air layer added at the same thickness of 20 mm. As can be seen in the figure, those indicated by the subscript '' exhibit a sound absorption coefficient of 0.70 at 630Hz, and those indicated by ''' exhibit a sound absorption coefficient of 0.95 at 500Hz.In this way, by adding an air layer, for example, 10 mm
In the case of ′,″, the frequency is shifted to the 1/2 octave lower frequency side according to the increase of 20 mm from
By adding an air layer of mm, it is possible to greatly shift the frequency to the low frequency side by 11/2 octaves. It has been confirmed through experiments that if the molecular weight is kept even lower, the resonance point of the material will move closer to the lower frequency side. Next, an example will be shown in which the theory described above is applied to a soundproof structure. FIG. 4 shows a longitudinal cross-sectional view of the same, and numeral 1 is a frame made of aluminum extrusion.
On the sound source side, a high molecular weight transparent oil-extended synthetic rubber thin film body 2 (film thickness 1 mm) described in the present invention is uniformly stretched with bolts 3 to protruding parts 1a, 1a provided opposite to the frame body. It is set up. In the figure, 3a indicates a nut, and 3b indicates a metal packing. Projecting parts 1a', 1 formed on the frame 1 on the side opposite to the sound source side
A transparent plastic sound plate 4 (for example, an acrylic resin plate) is attached to the bolt 3 and the metal packing 3b.
The space between the rubber thin film body and the tone plate forms a resonant air layer 5. The frame 1 used is one in which a vertical frame and a horizontal frame of the same shape are assembled in advance using mold fittings 6 and bolts so as to form a picture frame shape. The sound plate 4 can be sufficiently used as long as it has a certain strength and is made of transparent plastic material, and it goes without saying that the sound performance will be influenced by the selection of its mass. Therefore, the thickness of the plate is determined by taking into consideration the strength and sound performance. FIG. 5 shows a three-layer structure as a representative example of a sound-absorbing structure in which transparent synthetic rubber thin film materials are stretched in multiple layers according to the present invention. Symbols corresponding to those in FIG. 4 appear in the same manner. The frame constitutes a front part 1a, a middle part 1a'', and a rear part 1a', and a high molecular weight transparent oil-extended synthetic rubber thin film material 2 and a middle part are inserted between the front part 1a and a spacer 7. A molecular weight transparent non-oil extended synthetic rubber thin film material 2' (thickness 1 mm) is uniformly stretched with bolts, metal packing and nuts, and a resonant air layer 5' is formed between each member.The central protruding portion 1a'' In between is a thin film of low molecular weight transparent non-oil extended synthetic rubber 2″ (thickness 1mm)
are uniformly tensioned with bolts, metal packing and nuts, and a resonant air layer 5'' is formed between both members.Furthermore, a transparent plastic sheet and tone plate 4 are attached to the rear protruding portion 1a' by bolts, metal packing and nuts. It is stretched by packing and nuts, and a resonant air layer 5 is formed between both members.The medium-high molecular weight synthetic rubber thin film material and the low molecular weight synthetic rubber thin film material, which are not oil-extended, increase the sound absorption coefficient by themselves. What cannot be achieved is as pointed out in the explanation of equation (1) and Figure 2.Of course, the sound absorption coefficient can be further increased if all three layers are covered with high molecular weight oil-extended synthetic rubber thin film materials. Furthermore, if necessary, a multi-layer structure can be constructed by combining an oil-extended synthetic rubber thin film material and a non-oil-extended rubber thin film material.In the illustrated example, the thickness of the resonant air layer is 6 mm for the primary air layer 5', and The next air layer 5'' is 20 mm, and the tertiary air layer 5 is 30 mm. FIG. 6 is a chart showing the experimental results of the normal incidence sound absorption coefficient of the composite sound absorbing structure excluding the inner part and sound plate 4 of the structure shown in FIG. The thickness of the molecular weight synthetic rubber (SBR) thin film material is 1 mm, the thickness of the primary resonant air layer 5' is 6 mm, and the thickness of the secondary resonant air layer 5'' is 20 mm behind the thin film material 2''. The thickness of the air layer is 30mm. As seen in the figure, the low frequency side was able to cover frequencies below 200Hz, and the high frequency side was able to exhibit high sound absorption coefficients up to 1600Hz and above due to the high molecular weight synthetic rubber thin film material. It should be noted that by reducing the thickness of the resonant air layer, the peak shifts to the high frequency side, so it is possible to reduce the drop in the sound absorption coefficient in the middle of 400 Hz, as mentioned in the explanation of adding an air layer in the main text. That's right. Further, as the thickness of the thin film material increases, the transparency decreases, so it is desirable to determine the appropriate film thickness in consideration of transparency and film strength. As described above, the present invention provides effects such as being able to provide a sound absorbing structure with a simple structure and exhibiting excellent sound absorption coefficient, and also being able to provide a structure that does not damage the landscape and environment.

[Brief explanation of the drawing]

Figure 1 is a history diagram showing the tensile stress-elongation curve of the SBR thin film material, Figure 2 is a chart showing the experimental results of normal incidence sound absorption coefficient of a single SBR thin film material, and Figure 3 is a graph showing the addition of an air layer and the perpendicular A diagram of the experimental results showing the relationship with the incident sound absorption coefficient, FIG. 4 is a basic configuration diagram showing the sound absorbing structure of the present invention, FIG. 5 is a sectional view showing an example of the composite sound absorbing structure of the present invention, and FIG. 6 is a chart showing an example of the sound absorption effect of the sound absorption structure of the present invention. Explanation of symbols, 1... Frame body, 2, 2', 2''... Transparent synthetic rubber thin film material, 3... Bolts, 4... Transparent plastic sheet and tone plate, 5, 5', 5'', 5... Resonant air layer .

Claims (1)

[Claims] 1. A transparent oil-extended synthetic rubber thin film material is stretched on the sound source side of the opposing frames, a transparent plastic sheet or tone plate is stretched on the side opposite to the sound source side, and the stretched A sound absorbing structure made of a transparent synthetic rubber thin film material in which a resonant air layer is formed in the space formed between the rubber thin film material and the tone plate. 2 A transparent oil-extended synthetic rubber thin film material is stretched on the sound source side of the opposing frames, a transparent plastic sheet or tone plate is stretched on the opposite side of the sound source side, and a transparent oil-extended rubber film is stretched between the two stretched members. Synthetic rubber thin film materials, transparent non-oil-extended synthetic rubber thin film materials with different molecular weights, or a combination of these, one or several thin rubber film materials are stretched at predetermined intervals, and resonance occurs in the spatial region formed by each of the rubber thin film materials. A composite sound-absorbing structure made of transparent synthetic rubber thin film material with an air layer formed therein.