Patent ID: 8393438

Claim:
A multilayered sound absorbing material comprising a sound absorbing material and a porous sheet wherein said sound absorbing material consists of a fiber sheet made of fibers containing at least 50% by mass of a porous fiber having many minute pores, each minute pore opening onto the surface of said fiber, said sound absorbing material having a unit weight in the range of between 10 and 50 g/m 2 and an airflow resistance in the range of between 0.05 and 3.0 kPa·s/m, wherein said porous fiber is a porous pulp fiber having a beating or refining degree in the range of between 350 and 650 ml on the basis of Canadian Standard Freeness (CFS) provided in JIS P 8121-1995-4 Canadian Standard Freeness, or in the range of between 15 and 30° SR on the basis of Schopper-Riegler Freeness provided in JIS P 8121-1995-5 Schopper-Riegler Type Freeness Test Method, and said fiber sheet has contraction and expansion properties by carrying out crepe processing on said fiber sheet to provide a crepe processed fiber sheet having a creping degree in the range of between 10 and 50%, or carrying out embossing on said fiber sheet to provide an embossed fiber sheet having many projections, the height of each projection being in the range of between 0.02 and 2.00mm, with the number of said projections being between 20 and 200 projections/cm 2 and said porous sheet consists of a fiber sheet in which a thermoplastic fiber having a melting point below 180° C. is partially or wholly used and said sound absorbing material and said porous sheet are bonded together by an air-permeable hotmelt adhesive layer to secure the air-permeability of the resulting mutilayered sound absorbing material.