DETERMINATION OF SOUND ABSORPTION OF DOUBLE MICRO-PERFORATED ABSORBERS BY TWO ANALYTICAL METHODS

Micro-perforated panels (MPP) present an increasing use in terms of acoustic energy absorption capacity, efficient design and simulation. A double micro-perforated absorber (DMPA) is formed by two micro-perforated panels placed in parallel backed by a rigid wall, and it is based on the principle of Helmholtz resonator which presents a small opening connected to a closed volume of air. The air space can be filled partially or completely with different sound-absorbing materials. The analytical models used to calculate sound absorption coefficient are based on the electrical equivalent circuit of the structure and the transfer matrix method. The compatibility of these two methods is observed and analyzed in order to improve them. Both methods imply the models predicted by Maa for the acoustical resistance and reactance of the MPPs.