Recent Developments in Applications of Microperforated Panel Absorbers

Microperforated panel (MPP) absorbers are promising as a basis for the next-generation of sound absorbing materials. A microperforated panel absorber is backed by an air-cavity with a rigid-back wall and its typical use is for a sound-absorbing ceiling. However, MPPs have some limitations and disadvantages: its sound absorbing mechanism is limited to a Helmholtz resonator caused by perforations with air-cavity and effective absorption is limited to the resonance frequency range. There is also a problem when MPPs are used as a sound absorbing finish of room interior surfaces because typical MPPs are made out of thin limp materials and are not strong enough. In order to solve these problems, the research at Kobe University has focussed on the followings: (1) application of MPPs for room interior surface finishings, including applications of honeycomb MPPs, (2) multiple-leaf MPP absorbers. The main results from these projects are reviewed in this paper.