Evaluating Various Models of Perforated Plate and Porous Absorber

Abstract

Perforated plate is a thin panel with periodic arrangement of small perforations in front of air gap which prevents the sound waves passing through it. Present work explains the different mathematical models for perforated plate and porous absorber. Two methods for finding the absorption coefficient have been discussed. It has been shown that perforated plate can also be modeled as equivalent fluid approach following the work of Johnson-Champoux-Atalla with an equivalent tortuosity. Four different cases have been taken for consideration and are solved by methods namely transfer matrix method and impedance transfer matrix. It has been found that both the methods give same result. Transfer matrix method is easy to use but using impedance transfer method for multilayer structure is a tedious task. Various geometric dimensions of perforated plate and porous absorber has been varied and the effects for sound absorption has been discussed. For the validation of analytical solutions 11 different samples of perforated plate and 10 different samples of porous absorber has been taken and compared from experimental results available in different literature. It was found that perforated plate gives better sound absorption than porous absorber at lower frequency. The effects of adding layers of plate and porous absorber have also been investigated.