Site News  |   Monitor Keywords  |   Monitor Archive  |   Organizer  |   Account Info  |

Sound absorbing material and structure using the same

This invention relates to a sound absorbing material and a structure using the same. In particular, this invention relates to the sound absorbing material and the structure using the same which absorbs noise of high-frequency band beyond 200 Hz as well as low-frequency band of 200 Hz or less effectively and can improve the degree of freedom of the product form.

Heretofore, as the sound absorbing material of this kind, (a) the thing which uses a porous layer comprising a glass wool or a rock wool, and so on; (b) the thing which has an air layer in the sound source side; (c) the thing which has an air layer in the sound source side of the sound absorbing material; (d) the thing which laminates the aggregates of the high density and low density fibers more than at least two layers that the air permeability are different approximately 5-100 times; are known (for example, refer to patent document No. 1).

However, in the sound absorbing materials of (a) and (b), for the noise of the frequency band beyond 500 Hz or for the noise of the frequency band of 500 Hz or less, it is necessary to thicken the thickness of the porous layer to bring out the required sound absorbing effect. Consequently, there was a difficult point that the weight of the sound absorbing material becomes heavy. And, in the sound absorbing materials of (c), because there is the air layer in the sound source side of the sound absorbing material, there were difficult points that the weight of the sound absorbing material became heavy and it was necessary to widen the space. Meanwhile, in the sound absorbing materials of (d), by laminating the aggregates of fibers having different density additionally to the porous sound absorbing structure which absorbs sound by using the viscous resistance of the air and by converting the energy of the sound wave to thermal energy, the high density part plays the role of the mass and the low density part plays the role of the spring. That is, so-called dynamic vibration absorber is composed and the sound absorption coefficient is improved in low-frequency band especially. Regarding the sound absorbing material of this kind of structure, there was a difficult point that the sufficient sound absorbing effect is not obtained in so-called low-frequency band of 100 Hz or less especially. In addition, because the sound or the vibration in the low-frequency band is generated by shaking of the building or the window as well as air-borne sound, it is necessary to take the prevention measures of the structure-borne sound and vibration concurrently. Therefore, it was difficult to take the prevention measures about the sound absorbing material known in the conventional technology.

For this reason, previously, the applicant of this invention developed the sound absorbing material which laminated the aggregate of fibers having different density additionally to the porous sound absorbing structure which absorbed sound by using the viscous resistance of the air and by converting the energy of the sound wave to the thermal energy. And the applicant of this invention filed the invention as a patent (Japanese Patent Publication No. 2003-316364).

This sound absorbing material has the foam layer placed in the sound source side and has the porous layer laminated on the rigid wall side of this foam layer. Here, the foam layer is formed by foam including each ingredients, that is, first diol of molecular weight 500-5000, second diol of molecular weight 500 or less, inorganic filler, water as the blowing agent and isocyanate. And the porous layer is formed by general-purpose glass wool.

Regarding the sound absorbing material of this kind of structure, the high density part plays the role of the mass and the low density part plays the role of the spring. Therefore, so-called dynamic vibration absorb is composed, and the sound absorption coefficient can be improved in low-frequency band especially.

However, in the sound absorbing material of this kind of structure, there were following difficult points.

First, because the flame retardancy is not given to the sound absorbing material itself, this sound absorbing material does not fit the standard of the flame retardancy of the Building Standard Law.

Second, in the glass wool which composes the porous layer, the sound absorbing effect becomes weak in the high-frequency band beyond 200 Hz or in the low-frequency band of 200 Hz or less.

Third, because the foam layer and the porous layer are composed individually, the construction on the site becomes complicated.

Patent document No. 1: Japanese Patent Publication No. Hei08-152890 Patent document No. 2: Japanese Patent Publication No. 2003-316364

This invention aims to provide the sound absorbing material and the structure using the same which can absorb the noise of high-frequency band beyond 200 Hz as well as low-frequency band of 200 Hz or less effectively and can improve the degree of freedom of the product form.

A sound absorbing material as the first feature of this invention comprises a film which is composed of a rubber, and a porous layer which is laminated on a back surface of the film.

The sound absorbing material as the second feature of this invention comprises the film which is composed of the rubber, and the porous layer which is laminated on the back surface of the film, and an another porous layer which is laminated on a front surface of the film.

According to the third feature of this invention, in the sound absorbing material of the first feature or the second feature, the rubber is composed of a silicone rubber.

According to the fourth feature of this invention, in the sound absorbing material of any one of the features form the first to the third, a heat release value of combustion of the film is 8 MJ/m2 or less.