25 years (transparent) micro-perforated sound absorbers

The theory of microperforated sound absorbers (MPA) has been introduced by D.-Y. Maa in 1975. Micro-perforated sound absorbers have been used in various applications. Materials that have been used to be micro-perforated have been 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 toward sustainable sound absorption.