Estimation of effective parameters for microperforated panel absorbers and applications

Microperforated panel absorbers are used in many noise control applications as an alternative to fibrous materials. In the past, perforations were circular in shape. However, perforations are now often pressed or cut into the metal. They are non-circular and are irregular shaped and are difficult to model. A nonlinear least squares data-fitting algorithm is utilized to estimate geometric parameters from measured absorption coefficient data. The circular perforation model proposed by Maa is used in the algorithm. The estimated geometric parameters are then used to calculate transfer impedance with good agreement compared to measured data. The procedure is then used to aid in understanding the effect of manufacturing variations, and dust and fluid contamination on the performance of microperforated panel absorbers.