LAMINATED SOUND ABSORPTION MATERIAL

To provide a laminated sound absorption material which is lightweight, and has high sound absorption performance at low to high frequencies of 300 to 2,000 Hz.SOLUTION: A laminated sound absorption material 4 includes a non-woven fabric layer 1 having unevenness, and dry type non-woven fabric layers 5a to 5d, wherein the non-woven fabric layer 1 having the unevenness has fiber density of 50 kg/m3 or more and 500 kg/m3 or less, and is arranged in front of the dry type non-woven fabric layers 5a to 5d when being viewed from a sound injection direction, the dry type non-woven fabric layers 5a to 5d have both flat main surfaces, one or a plurality of layers of the dry type non-woven fabric layers 5a to 5d exists, and mass per unit area of the laminated sound absorption material 4 is 2,800 g/m2 or less. Preferably, a vertical incident sound absorption rate at 300 Hz of the laminated sound absorption material 4 is 40% or more, and the vertical incident sound absorption rates at 500 Hz, 1,000 Hz and 2,000 Hz are 55% or more.SELECTED DRAWING: Figure 2 【課題】軽量であり、３００Ｈｚ～２０００Ｈｚの低周波領域～高周波数における吸音性能が高い積層吸音材を提供する。【解決手段】凹凸を有する不織布層１と、乾式不織布層５ａ～５ｄを含む積層吸音材４であって、凹凸を有する不織布層１は、密度が５０ｋｇ／ｍ3以上５００ｋｇ／ｍ3以下であり、音の入射方向から見て乾式不織布層５ａ－５ｄの前に配置されており、乾式不織布層５ａ～５ｄは両主面がフラットであり、１層又は複数層存在し、積層吸音材４の単位面積当たりの質量が２８００ｇ／ｍ2以下である。積層吸音材４の３００Ｈｚにおける垂直入射吸音率が４０％以上、５００Ｈｚ、１０００Ｈｚ及び２０００Ｈｚにおける垂直入射吸音率がそれぞれ５５％以上であることが好ましい。【選択図】図２