Acoustic transmission analysis of multi-layer absorbers

A simple but accurate analytical acoustic transmission analysis (ATA) is developed for evaluating the acoustic absorption of the multi-layer acoustic absorber. Unlike other analytical approaches available in literature, the present ATA can deal with the multi-layer acoustic absorber containing several compartments. Each compartment may include the layers of perforated plates, airspaces and porous materials together. The continuity of the particle velocity at the interfaces among perforated plates, airspaces and porous materials is assumed. The effects of the back surface acoustic impedance of both airspaces and porous materials are also taken into account. After combining those compartments, the resultant acoustic impedance and acoustic absorption coefficient of the multi-layer acoustic absorber can be obtained. For demonstration, four different types of multi-layer acoustic absorbers are analyzed. The results are also verified by relevant experiments or finite-element analysis. Finally, several important influence factors that affect the acoustic absorption of the multi-layer acoustic absorber are discussed. (C) 2001 Academic Press.