JP4167673B2 - Membrane sound absorbing structure - Google Patents

Description

The present invention relates to a film-like sound absorbing structure , and more particularly to a film-like sound absorbing structure capable of effectively absorbing noise in a low frequency region of 200 Hz or less with a single film.

  Conventionally, as this kind of sound absorbing material, (a) one using a porous body layer made of glass wool, rock wool or the like, (b) one comprising an air layer behind the sound absorbing material, (c) air permeability Are formed by laminating at least two layers of high-density and low-density fiber assemblies differing by 5 to 100 times (see, for example, Patent Document 1).

  However, in the sound-absorbing material (a), in order to exhibit a required sound-absorbing effect with respect to noise having a frequency band of 500 Hz or less, the thickness of the porous body layer must be increased. There was a problem that the weight of the sound absorbing material was increased overall. In the sound absorbing material (b), the weight of the back air layer formed between the plate-like or film-like film-like sound absorbing material and the rigid wall and the plate-like or film-like film-like sound absorbing material is spring-mass type. The sound absorption mechanism of the resonance system is configured to reduce the air-borne sound generated from the sound source. In such a sound absorption structure, although the sound absorption peak can be estimated, the high sound absorption There is a difficulty that a sound-absorbing structure having a high rate cannot be realized. In addition, the current film-like sound absorbing material has a drawback in that an emphasis is placed on its price and ease of construction, and a material having a high sound absorption rate has not been selected. Furthermore, the sound-absorbing material (c) uses the viscous resistance of air, and by laminating fiber assemblies having different densities on a porous sound-absorbing structure that absorbs sound by converting sound wave energy into heat energy, The high-density part is an additional mass, and the low-density part plays the role of a spring, so that a so-called dynamic vibration absorber is constructed to improve the sound absorption coefficient particularly in the low frequency band. In particular, in a so-called low frequency band of 50 Hz or less, there is a problem that a sufficient sound absorbing effect cannot be obtained. In addition, sound and vibration in the low frequency band generate not only air propagation sound but also rattling of buildings and windows, so it is necessary to take measures against solid propagation sound and vibration prevention at the same time. The countermeasure was difficult.

  For this reason, the present applicant firstly uses a viscous resistance of air to convert sound wave energy into thermal energy and absorbs sound, and then a sound absorbing material in which fiber assemblies having different densities are laminated. Has been developed and applied (Japanese Patent Laid-Open No. 2003-316364).

  The sound absorbing material includes a foam layer disposed on the sound source side and a porous body layer laminated on the rigid wall side of the foam layer. Here, the foam layer is formed of a foam containing a first diol having a molecular weight of 500 to 5000, a second diol having a molecular weight of 500 or less, an inorganic filler, water as a foaming agent, and isocyanate. Moreover, the porous body layer is formed of general-purpose glass wool.

  According to the sound absorbing material having such a configuration, a so-called dynamic vibration absorber, in which the high density portion plays the role of additional mass and the low density portion plays the role of spring, can improve the sound absorption coefficient particularly in the low frequency band. .

However, in the sound absorbing material having such a configuration, firstly, glass wool constituting the porous body layer has a drawback that the sound absorbing effect is weakened in a low frequency region of 150 Hz or less , and secondly , the foam layer. And the porous body layer are integrally molded, and a surface film is formed on the sound source side of the foam layer during the integral molding, so that the degree of freedom of the product cannot be improved. In other words, since the surface film is formed at the same time when the foam layer and the porous body layer are integrally formed, in order to exhibit the required sound absorption characteristics, the sound source side of the foam layer and the rigidity of the porous body layer are required. There was the difficulty that the wall side had to be changed.

JP-A-8-152890 JP 2003-316364 A

The present invention provides a film-like sound absorbing structure capable of realizing a high sound absorption rate by adjusting the vibration damping property of a single film, and particularly capable of effectively absorbing noise in a low frequency region of 200 Hz or less. The purpose is that.

The film-like sound absorbing structure according to the first aspect of the present invention is arranged on the sound source side of a rigid wall in parallel with the rigid wall, and itself has a vibration-damping property, and the film-like sound absorbing material. A back air layer between the material and the rigid wall, when the mass per unit area of the film-like sound absorbing material is m (kg / m ² ) and the thickness of the back air layer is L (m) , ML ≧ 7 / (8π2)
Membranous sound absorbing structure which satisfies the condition.

According to a second aspect of the present invention, in the film-like sound absorbing structure according to the first aspect, the film-like sound absorbing material is made of a film having damping properties, and the loss coefficient of the film is 0.04 or more. Is.

According to a third aspect of the present invention, in the film-like sound absorbing structure according to the first aspect, the film-like sound absorbing material is made of a film having damping properties, and the loss coefficient of the film is 0.1 or more. Is.

The film-shaped sound-absorbing material according to the fourth aspect of the present invention is the film-shaped sound-absorbing material according to the second aspect or the third aspect, wherein the air permeability of the film is 0.1 dm ³ / s or more. Is.

A fifth aspect of the present invention, in any one of membranous sound absorbing material of the second to fourth aspects, the film is intended to be used in a frequency band 50～2000Hz.

A sixth aspect of the present invention, in any one of membranous sound absorbing material of the second aspect to the fifth aspect, the film is intended to be used in a frequency band 50～500Hz.

A seventh aspect of the present invention, in any one of membranous sound absorbing material of the second aspect to the sixth aspect, the coating is one that is made of a synthetic resin.

According to an eighth aspect of the present invention, in the film-like sound absorbing material according to the seventh aspect, the synthetic resin is at least one of a continuous foam and a closed foam, or a mixed foam of the continuous foam and the closed foam. It is what has been.

According to a ninth aspect of the present invention, in the film-like sound absorbing material according to the seventh aspect or the eighth aspect, the synthetic resin includes a first diol having a molecular weight of 500 to 5000, a second diol having a molecular weight of 500 or less, It is composed of a foamed material containing inorganic fillers, water as a foaming agent, and isocyanate components as raw material components.

According to a tenth aspect of the present invention, in the film-shaped sound absorbing material according to the ninth aspect, the density of the foam is 50 to 500 kg / m ³ .

According to an eleventh aspect of the present invention, in the film-shaped sound absorbing material according to the ninth aspect or the tenth aspect, the ratio of the hydroxyl group content contained in the first diol to the hydroxyl group content contained in the second diol. Is set to 1: 0.3 to 2.5.

A twelfth aspect of the present invention, the film-like sound absorbing material is any one of the ninth aspect to eleventh aspect of the content of the inorganic filler, 10 with respect to the first diol 100 parts by weight The amount is 200 parts by weight.

According to a thirteenth aspect of the present invention, in the film-shaped sound absorbing material according to any one of the ninth to twelfth aspects, the water content as the foaming agent is based on 100 parts by weight of the first diol. The amount is 2 to 5 parts by weight.

In a fourteenth aspect of the present invention, in the film-like sound absorbing material according to any one of the ninth to thirteenth aspects, the total of the hydroxyl content of water as the first and second diols and the foaming agent The isocyanate index (NCO / OH), which is the ratio of the isocyanate content to the isocyanate content, is in the range of 0.5 to 1.0.

According to a fifteenth aspect of the present invention, in the film-like sound absorbing material according to any one of the ninth to fourteenth aspects, the isocyanate index is in a range of 0.6 to 0.9. .

The 16th mode of the present invention, the film-like sound absorbing material is any one of the eighth aspect to the fifteenth aspect of the, the first diol, polyester polyol, polyether polyol, polybutadiene polyol, polyisoprene polyol, One of the diols selected from a polyolefin polyol, a polyacrylate ester polyol, and a polycarbonate polyol is used.

According to a seventeenth aspect of the present invention, in the film acoustic material according to any one of the ninth to sixteenth aspects, the second diol is ethylene glycol, propylene glycol, butanediol, hexanediol, or octanediol. Diol selected from aliphatics such as decanediol and aromatics such as N, N-bis (2-hydroxypropyl) aniline.

An eighteenth aspect of the present invention is the film-shaped sound absorbing material according to any one of the ninth to seventeenth aspects, wherein the inorganic filler is carbon black, silica, calcium carbonate, mica, talc, magnesium oxide, The inorganic filler is any one selected from aluminum oxide, magnesium hydroxide, and aluminum hydroxide.

According to a nineteenth aspect of the present invention, in the film-shaped sound absorbing material according to any one of the ninth to eighteenth aspects, the isocyanate is 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4 , 4′diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude tolylene diisocyanate, crude diphenylmethane diisocyanate, p-phenylene diisocyanate, p-xylene diisocyanate, tetramethylene-1,4-diisocyanate. It is what.

The 20th mode of the present invention, the film-like sound absorbing material is either a second aspect to the nineteenth aspect, the thickness of the film is what is 0.5 to 20 mm.

According to a twenty- first aspect of the present invention, in the film-like sound absorbing material according to any one of the first to twentieth aspects, a porous body is disposed in the back air layer.

According to a twenty-second aspect of the present invention, in the film-like sound absorbing structure according to the twenty-first aspect, the porous body is glass wool, rock wool, coarse wool felt, vegetable fiber felt, animal fiber felt, or synthetic fiber felt. Or a mixture thereof.

According to the film-like sound absorbing structure of the first to twenty- second aspects of the present invention, the use of the film-like sound absorbing material having a high sound absorption rate effectively absorbs noise in a low frequency region of 200 Hz or less. can do.

Embodiments to which the film-like sound absorbing structure of the present invention is applied will be described below with reference to the drawings.

First, in the film-like sound absorbing material used in the present invention , a film having a damping property with a loss coefficient tan δ of 0.04 or more is used. Here, the reason why the loss coefficient tan δ is set to 0.04 or more is that if it is less than 0.04, sufficient vibration damping performance cannot be obtained, and the sound absorption effect is reduced.

  As the above-mentioned film-like sound absorbing material, a film having a damping property with a loss coefficient tan δ of 0.1 or more is preferably used. Here, the loss coefficient tan δ is set to 0.1 or more because the sound absorption coefficient of the film-like sound absorbing material having the loss coefficient tan δ of 0.1 or more has a high sound absorption coefficient peak in the frequency band of 50 to 2000 Hz as described later. This is because sufficient damping properties can be obtained even with this film.

  In addition, the loss factor described above is obtained by measuring a sample having a length of 300 mm, a width of 25 mm, and a thickness of 25 mm at a temperature of 20 ° C. using a loss factor measurement system SA-74 manufactured by Rion Co., Ltd. according to a method in accordance with JIS G 0602. The test piece was bonded to a steel plate having a thickness of 1.5 mm, the test piece was held by a central support method, and the test piece was vibrated with an electromagnetic vibrator to calculate by the half width method.

Next, in the film-like sound absorbing material used in the present invention , a film having vibration damping properties with an air permeability of 0.1 dm ³ / s or more and a thickness of 20 mm or less is used. Here, the air flow rate was set to 0.1 dm ³ / s or more. When the air flow rate was less than 0.1 dm ³ / s, the air in the gap portion of the porous body constituting the film vibrated as described later, This is because the mechanism of absorbing sound by converting the energy of sound waves into thermal energy by the viscous resistance of air does not work sufficiently.

  In addition, said ventilation | gas_flowing amount was measured by the air permeability measurement method (B method) of JISK6400 and a flexible urethane foam test method.

  As such a vibration-damping film, a synthetic resin, in particular, a synthetic resin composed of at least one of continuous foam and closed foam, or a synthetic resin composed of a mixed foam of continuous foam and closed foam is used. It is done. This is because, when sound waves are incident on the foam that constitutes the synthetic resin, the air in the gaps vibrates, the sound wave energy is converted into thermal energy by the viscous resistance of the air, and sound damping is also achieved. This is because the foam itself vibrates and the sound wave energy is converted into heat energy by the viscous resistance at this time, and sound absorption is performed.

  A film made of a synthetic resin having such vibration damping properties is formed of the following foam.

  First, the foam is composed of a first diol having a molecular weight of 500 to 5000, a second diol having a molecular weight of 500 or less, an inorganic filler, water as a foaming agent, and an isocyanate component. By making the first diol, which is the main polymer, a diol having a molecular weight of 500 to 5000, and preferably a molecular weight of 1000 to 2000, it is possible to obtain a foam with added vibration damping properties. Here, when the main polymer is composed of a diol having a molecular weight of less than 500, a hard foam is obtained and vibration damping properties cannot be obtained. The body cannot be obtained. When a polyol other than triol or the diol used in the present invention is used as the main polymer, it is difficult to obtain vibration damping properties.

Second, the density of the foam is preferably in the range of 50 to 500 kg / m ³ . If the density is less than 50 kg / m ³ , the air permeability becomes too good, and the sound absorption efficiency in the low frequency region is deteriorated. If the density exceeds 500 kg / m ³ , the air permeability becomes too bad and the sound is reflected and the sound absorption is difficult. Because it becomes.

  Thirdly, as the first diol constituting the foam, polyester polyol, polyether polyol, polybutadiene polyol, polyisoprene polyol, polyolefin polyol, polyacrylic ester polyol, polycarbonate polyol and the like are suitable.

  Fourth, the second diol constituting the foam is used as a chain extender of the foam layer 1 of the present invention and plays a role of reinforcement. Here, the reason why the molecular weight is 500 or less is that if the molecular weight exceeds 500, the reinforcing effect cannot be obtained. Further, when this component is a polyol other than triol or diol used in the present invention, the reinforcing effect becomes too great and the vibration damping property is impaired.

  Fifth, the second diol constituting the foam may be an aliphatic group such as ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, decanediol, or N, N-bis (2-hydroxypropyl). Aromatic diols such as aniline are preferred.

  Here, the ratio of the hydroxyl group content contained in the first diol used in the foam and the hydroxyl group content contained in the second diol is preferably 1: 0.3 to 2.5. This is because if the ratio of the hydroxyl group content of the second diol is less than 0.3, the reinforcing effect becomes insufficient, and even if the ratio of the hydroxyl group content exceeds 2.5, no difference in effect is observed.

  Sixth, the inorganic filler constituting the foam is used for the purpose of reinforcing the foam layer and adding damping properties. This inorganic filler is preferably blended in an amount of 10 to 200 parts by weight per 100 parts by weight of the first diol having a molecular weight of 500 to 5000. If the amount is less than 10 parts by weight, the effect of adding sufficient reinforcement and vibration damping is small, and if it exceeds 200 parts by weight, the viscosity of the composition before molding becomes high and molding becomes difficult.

  Seventh, as the inorganic filler constituting the foam, carbon black, silica, calcium carbonate, mica, talc, magnesium oxide, aluminum oxide, magnesium hydroxide, aluminum hydroxide and the like are suitable.

  Eighth, water constituting the foam is used as a foaming agent. Although the addition amount of a foaming agent should just be the quantity from which a foam is obtained, 2-5 weight part is suitable with respect to 100 weight part of 1st diols with a molecular weight of 500-5000. This is because if the amount is less than 2 parts by weight, sufficient foaming is not performed, and if the amount exceeds 5 parts by weight, no significant difference in effect is observed.

  Ninthly, as the isocyanate constituting the foam, basically those used for the production of urethane foam can be used, and in particular, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude tolylene diisocyanate, crude diphenylmethane diisocyanate, p-phenylene diisocyanate, p-xylene diisocyanate, tetramethylene-1,4-diisocyanate and the like are suitable. Can be used as a mixture.

  Tenth, in order to impart moderate rigidity and vibration damping to the foam, the ratio of the total hydroxyl group content of the first diol, the second diol, and water as the blowing agent to the isocyanate content of the isocyanate It is desirable that the isocyanate index (NCO / OH) is in the range of 0.5 to 1.0, preferably 0.6 to 0.9. This is because if the isocyanate index is less than 0.5, the degree of cross-linking decreases and rigidity decreases, and if it exceeds 1.0, moderate rigidity is obtained, but vibration damping performance decreases.

  11thly, you may add suitably the catalyst used for manufacture of a normal urethane foam layer, a foaming agent, a flame retardant, a plasticizer, a coloring agent, etc. to said foam according to the objective.

FIG. 1 shows the measurement results of the loss factor for evaluating the vibration damping properties of the film-like sound absorbing material used in the present invention.

Here, in the figure, a solid line L1 is a loss coefficient of the film-like sound absorbing material used in the present invention , a dotted line L2 is a loss coefficient of a conventional film-like sound absorbing material made of a general sound-absorbing polyurethane foam, and an alternate long and short dash line L3 is The loss coefficient of a conventional film-shaped sound absorbing material made of glass wool is shown. From the figure, the film-like sound absorbing material used in the present invention has a large loss coefficient in the frequency band of 40 to 3000 Hz and high vibration damping properties compared with glass wool and general polyurethane foam for sound absorption. I understand. In particular, in the frequency band of 50 to 2000 Hz, it can be seen that the film-shaped sound absorbing material used in the present invention having a loss coefficient of 0.1 or more has high vibration damping properties.

FIG. 2 shows a side view of a film sound absorbing structure using the film sound absorbing material in the present invention.

  In the figure, the film-like sound absorbing structure of the present invention includes a film-like sound absorbing material 3 attached to the sound source side of the rigid wall 1 in parallel with the rigid wall 1 via a pair of support members 2a, 2b, and a film-like sound absorbing material 3 And a back air layer 4 defined by the rigid wall 1.

  In the film-shaped sound absorbing structure having such a configuration, the back air layer 4 acts as a spring with respect to the mass of the film-shaped sound absorbing material 3 to form a single resonance system, and the frequency of the sound wave is that of the single resonance system. When the resonance frequency coincides, the film-like sound absorbing material 3 vibrates and is absorbed by internal friction.

Here, the resonance frequency fr of such a film-like sound absorbing structure is such that the mass per unit area of the film-like sound absorbing material 3 is m (kg / m ² ) and the thickness of the back air layer 4 is L (m). , Expressed by Equation 1.

However, p: density of air, c: sound speed Here, when the resonance frequency fr in the above equation is 200 Hz, a combination of a film-like sound absorbing structure having a sound absorbing peak at 200 Hz or less can be obtained. That is, in the film-like sound absorbing structure of the present invention, in order to have a sound absorption peak at a frequency of 200 Hz or less, the combination of the mass per unit area of the film-like sound absorbing material 3 and the thickness of the back air layer 4 is It is necessary to satisfy the conditions.

  From the above equation, an equation of 7 / (8π2) ≦ mL can be obtained. Therefore, if the condition of mL ≧ 7 / (8π2) is satisfied, a film-like sound absorption structure having a sound absorption peak at 200 Hz or less can be provided.

  FIG. 3 shows the relationship between the mass per unit area of the film-shaped sound absorbing material 3 and the thickness of the back air layer 4 in the film-shaped sound absorbing structure of the present invention having a sound absorption peak at 200 Hz or less. Here, in the film-like sound absorbing structure where the area S1 has a sound absorption peak at 200 Hz or less, a desirable region of the mass per unit area of the film-like sound absorbing material and the thickness of the back air layer is shown. From the figure, in the range where the mass per unit area of the membranous sound absorbing material is large, the sound absorption peak can be increased even if the thickness L of the back air layer is thin, and the mass per unit area of the membranous sound absorbing material is It can be seen that the sound absorption peak can be increased by increasing the thickness L of the back air layer within a small range.

  Next, the thickness of the film-like sound absorbing material 3 is preferably 0.5 to 20 mm. Here, the thickness of the film-like sound absorbing material 3 is set to 0.5 to 20 mm because if the thickness is less than 0.5 mm, the sound absorbing effect due to the vibration of the skeleton portion of the foam constituting the film is reduced, and the thickness is reduced. This is because if the thickness exceeds 20 mm, the vibration of the film decreases and the sound absorption effect decreases.

  FIG. 4 is an explanatory diagram of sound absorption characteristics in the film-like sound absorption structure shown in FIG. Here, the solid line L4 is a sound absorption characteristic in a conventional film-like sound absorbing structure using a low-density polyethylene film (thickness 0.5 mm) as a film having vibration damping properties, and the dotted line L5 is a film having vibration damping properties, The sound absorption characteristics of the film-like sound absorbing structure of the present invention using a foam made of a synthetic resin having a loss factor of 0.01 and a thickness of 0.5 mm are shown. The weight of the film in the present invention and the conventional example is the same, and the thickness of the back air layer is 50 mm. From the figure, it can be seen that the film-like sound absorption structure using the film according to the present invention exhibits superior sound absorption characteristics in the frequency band of 315 to 400 Hz than the conventional one.

  FIG. 5 shows a side view of a film-like sound absorbing structure in another embodiment of the present invention. In the figure, parts common to those in FIG. 2 are denoted by the same reference numerals and detailed description thereof is omitted.

  In FIG. 5, in this embodiment, a porous body 5 is disposed in the back air layer 4. The porous body 5 is disposed in the back air layer 4 densely or with a gap.

  In this embodiment, the vibration damping effect can be further improved as compared with the film-like sound absorbing structure shown in FIG.

  Here, the porous body 5 is formed of the following.

  First, the porous body 5 is made of glass wool, rock wool, coarse wool felt, vegetable fiber felt, animal fiber felt, synthetic fiber felt, or a mixture thereof.

  Second, the porous body is formed with a thermal conductivity of 0.1 to 0.5 W / mK.

  Thirdly, the porous body is formed of a urethane foam or a urethane foam base material blended with a thermal conductivity imparting material. Here, as the thermal conductivity imparting material, one selected from those composed of ceramics or metal materials, silicon carbide powder, alumina powder, aluminum powder, graphite, copper powder, stainless steel powder, or 2 of these. A mixture of at least seeds or graphite (the amount of graphite added is 10 to 150 parts by weight with respect to 100 parts by weight of the polyol forming the urethane foam) is used.

  The porous body having such a structure is attached to a sound source such as an engine, and has a sound absorbing performance effective for reducing air-borne sound, solid-borne sound, and vibration generated from the engine. Therefore, even if the temperature in the room or the soundproof box rises, the temperature rise of the porous body can be suppressed, and the life is prolonged without being deteriorated.

  In the above-described embodiments, the case where the film-like sound absorbing material is formed of a single foam having a uniform foam density is described, but the following may be used. For example, firstly, a foam having open cells inside, in which a thin film layer is integrally formed with the foam on the surface on the sound source side, and secondly, a thin film having a thickness of, for example, 1 mm or less The layer is integrally molded with both the sound source side and the rigid wall side foam; third, the foam density of the open-cell foam is different in the thickness direction; A plurality of different open-cell foams laminated such that the foam density is inclined, and fifth, the foam density of the open-cell foam is high on the sound source side, As the open cell foam, a material made of a viscoelastic material may be used.

Explanatory drawing which shows the measurement result of the loss factor for evaluating the damping property of the film-form sound-absorbing material used in this invention. The side view of the film-like sound absorption structure of this invention. Explanatory drawing which shows the relationship between the mass per unit area of the film-form sound-absorbing material in the film-form sound absorption structure of this invention, and the thickness of a back air layer. Explanatory drawing of the sound absorption characteristic in the film-form sound absorption structure of this invention. The side view of the film-like sound absorption structure in the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rigid wall 3 ... Membrane sound-absorbing material 4 ... Back air layer 5 ... Porous body

Claims (22)

A film-like sound absorbing material that is arranged in parallel to the rigid wall on the sound source side of the rigid wall and has damping properties by itself, and a back air layer between the film-like sound absorbing material and the rigid wall,
  The mass per unit area of the film acoustic material is m (kg / m ² ), When the thickness of the back air layer is L (m),
    mL ≧ 7 / (8π2)
A film-like sound absorbing structure characterized by satisfying the following conditions. 2. The film-like sound absorbing structure according to claim 1, wherein the film-like sound absorbing material is made of a film having vibration damping properties, and the loss coefficient of the film is 0.04 or more. The film-like sound absorbing material according to claim 1, wherein the film-like sound absorbing material is made of a film having vibration damping properties, and the loss coefficient of the film is 0.1 or more. Air permeability of the membrane-like sound absorbing structure according to claim 2 or claim 3, wherein the at 0.1dm 3 / ^s or more of the coating. The film-like sound absorbing structure according to any one of claims 2 to 4 , wherein the film is used in a frequency band of 50 to 2000 Hz . The film-like sound absorbing structure according to any one of claims 2 to 5 , wherein the film is used in a frequency band of 50 to 500 Hz . The film-like sound absorbing structure according to any one of claims 2 to 6 , wherein the film is made of a synthetic resin. 8. The film-like sound absorbing structure according to claim 7 , wherein the synthetic resin is at least one of a continuous foam and an independent foam, or a mixed foam of the continuous foam and the independent foam . The synthetic resin is composed of a first diol having a molecular weight of 500 to 5,000, a second diol having a molecular weight of 500 or less, an inorganic filler, water as a foaming agent, and a foam made from each component of isocyanate. The membranous sound absorbing structure according to claim 7 or 8, wherein The film-like sound absorbing structure according to claim 9 , wherein the foam has a density of 50 to 500 kg / m ³ . And a hydroxyl group content in the said first diol, the ratio of hydroxyl content contained in the second diol is 1: claim 9 or claim 10, wherein it is 0.3 to 2.5 Film-like sound absorbing structure. The film-like sound absorbing structure according to any one of claims 9 to 11 , wherein a content of the inorganic filler is 10 to 200 parts by weight with respect to 100 parts by weight of the first diol . The film-like sound absorbing structure according to any one of claims 8 to 12 , wherein a content of water as the foaming agent is 2 to 5 parts by weight with respect to 100 parts by weight of the first diol. . The isocyanate index (NCO / OH), which is the ratio of the total hydroxyl content of the first and second diols and water as a blowing agent to the isocyanate content of the isocyanate, is in the range of 0.5 to 1.0. membranous sound absorbing structure according to claim 9 to claim 13 any one of claims, characterized in that in the. The film-like sound absorbing structure according to any one of claims 9 to 14 , wherein the isocyanate index is in a range of 0.6 to 0.9 . The first diol is any diol selected from polyester polyol, polyether polyol, polybutadiene polyol, polyisoprene polyol, polyolefin polyol, polyacrylate polyol, and polycarbonate polyol. It claims 9 to 1 5 membranous sound absorbing structure according to any one of to. The second diol is selected from aliphatic systems such as ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol and decanediol, or aromatic systems such as N, N-bis (2-hydroxypropyl) aniline. The film-like sound absorbing structure according to any one of claims 9 to 16, wherein any one of the selected diols is selected . The inorganic filler is any inorganic filler selected from carbon black, silica, calcium carbonate, mica, talc, magnesium oxide, aluminum oxide, magnesium hydroxide, and aluminum hydroxide. membranous sound absorbing structure according to any one of claims 9 to 1 7. The isocyanate is 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4 ′ diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude tolylene diisocyanate, crude diphenylmethane diisocyanate, p-phenylene diisocyanate, p-xylene diisocyanate. The film-like sound absorbing structure according to any one of claims 9 to 18, wherein the isocyanate is selected from the group consisting of tetramethylene-1,4-diisocyanate . The film-like sound absorbing structure according to any one of claims 2 to 19 , wherein the film has a thickness of 0.5 to 20 mm . Membranous sound absorbing structure according to claim 1 to claim 20 any one of claims, characterized in that the porous body is disposed on the back air layer. The film-like sound absorbing device according to claim 21 , wherein the porous body is made of glass wool, rock wool, coarse wool felt, vegetable fiber felt, animal fiber felt, synthetic fiber felt, or a mixture thereof. Construction.

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