| 摘要 |
PROBLEM TO BE SOLVED: To improve efficiency of conversation clearness in a cabin by reducing noise level of a frequency band related to people conversation, especially a high frequency (1250Hz or higher) region. SOLUTION: A dash silencer 1 as the super light sound insulating material comprises a light sound absorption layer 2 and a porous resonance layer 3 made of non-ventilation material. The sound absorption layer 2 is formed in a complex layer of a high density sound absorption layer 2a and a low density sound absorption layer 2b, its whole thickness is 1-50 mm, and its whole density is 0.01-0.2 g/cm<SP>3</SP>. The resonance layer 3 is adhered to the sound absorption layer 2 via the sound absorption layer 2 and an adhesion layer 4, its eye amount is 1000 g/m<SP>2</SP>or less, and many holes 3a of 0.01-20 mm of diameter are formed at 1-10% of hole rate. The adhesive strength of the adhesion layer 4 to the sound absorption layer 2 and the resonance layer 3 is set to 1-20N/25mm in peeling at 180°and at peeling width of 25 mm, and the adhesion layer 4 is adhered to the whole interface of the sound absorption layer 2 and the resonance layer 3 in 50-100% of area. COPYRIGHT: (C)2006,JPO&NCIPI
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