Review on 50 years micro-perforated sound absorbers

50 years ago, in 1975, the theory of microperforated sound absorbers (MPA) has been introduced by D.-Y. Maa. Since then micro-perforated sound absorbers have been used in various applications. Starting in research facilities with absorbers made out of metal within China, the idea of micro-perforated sound absorbers has been applied to various materials such as metal, wood, plastics and many others. A short review of different applications of micro-perforation will be presented. This presentation will concentrate on applications in architectural acoustics. In 2000 the micro-perforation was introduced to transparent sheets making these highly sound absorptive. Over the past 25 years different set-ups made of micro-perforated layers, porous materials as well as plate resonators have been investigated. In this paper different applications of various set-ups with micro-perforated stretched foils will be presented. Day-light ceilings, mirror ceilings as well as absorbers in front of glass will be shown as well as newly developed day-light, sound absorptive and heating/cooling systems. The latest materials used for micro-perforation is a material made from wood and plants (up to 92 % natural ingredients). This replaces petroleum and opens new possibility towards sustainable sound absorption.