Abstract: In this paper was studied the influence of microstructures on the acoustical absorption properties of acoustical baffle, the blends of chlorined isobutyl-Isoprene rubber (CIIR) with the styrene butadiene rubber (SBR) or with nitrile rubber (NBR) with 36%~41% of acrylonitrile (CN). The acoustical baffle made of blend of SBR and CIIR, compared with NBR/CIIR, showed lower sensitivity to the changes within the hydrostatic pressure range of 0. 5 to 3 MPa and frequency range of 3. 5 to 7k Hz. And the acoustical absorption properties were better within the whole hydrostatic pressure and test frequency ranges, and the acoustical absorption property was the best within the lower frequency range of 1. 5~3. 5 k Hz.