An ideal absorbing materials in architectural acoustics: Micro-perforated panel absorbers

Abstract

Micro-perforated panel absorbers (MPA) can be used to reduce or better the noise in architecture. This absorber was developed in the 1960s, when a robust sound absorber was needed for severe environments, without porous materials. It has a simple structure and the absorption properties can be exactly calculated. The panel can be made of any materials from cardboard to plastic to plywood to sheet metal, for different purposes. Theoretical and experimental investigations on MPA are reviewed in this paper. By reviewing recent research work, this paper reveals a relationship between the maximum absorption coefficient and the limit of the absorption frequency bandwidth. It has been demonstrated that the absorption frequency bandwidth can be extended up to 3 or 4 octaves as the diameters of the micro-holes decrease. This has become possible with the development of the technologies for manufacturing MPA, such as laser drilling, powder metallurgy, welded meshing, and electro-etching to form micrometer-order holes. In this paper, absorption characteristics of such absorbers in random fields are presented and discussed both theoretically and experimentally. This review shows that the MPA has potentials to be an ideal absorbing materials in architectural acoustics in the 21st century.