Investigation on micro-perforated panel absorber with ultra-micro perforations

Micro-perforated panel (MPP) absorber has been widely used in noise reduction and is regarded as a promising alternative to the traditional porous materials. However, the absorption bandwidth of a single MPP is always insufficient to compete with the porous materials. Thus its practical application such as interior finish of room walls which has strict restrictions on space is prevented. According to Maa's theory, a possible approach to obtain high sound absorption over broad frequency band is to reduce the perforation diameter and increase the density of the perforation properly. And the absorption limits of a single MPP even can be obtained by reducing the perforation diameter to less than 100 mu m. However, it's difficult for traditional processing technology such as machining punching to fabricate such small perforations, thus MPPs with ultra-micro perforations have seldom been reported yet. In this paper, trial production of MPPs with ultra-micro perforations based on MEMS technology and measurement of their normal absorption coefficients were carried out. Results show that better absorption capability can be given with MPPs by using a ultra-micro perforation. Maa's conclusion that MPP absorbers can satisfy high sound absorption in broad frequency range by reducing the perforation diameter is therefore validated experimentally. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.