DefinePK

Abstract

This paper describes the analysis on the sound absorption characteristics of semi-permeable membrane absorber. The effects of membrane surface tension and backed-air gap distance on the sound absorption characteristics were investigated. The characteristics of the membrane absorber were measured experimentally in terms of Sound Absorption Coefficient, a and Noise Reduction Coefficient, NRC. The membrane is made of a thin, flexible, semi-permeable latex material and the tests were carried out by using impedance tube method according to ISO 10534-2 standard. The results showed that the surface tension has significant influence on the sound absorption characteristics. For the parameters used in the laboratory work, the specimen with un-stretched surface tension has the best absorption performance with 94% absorption at 1600 Hz. Membrane absorbers showed best performance at low-middle frequency region i.e. 1450-2000 Hz. The backed-air gap distances determine the location of sound absorption peak. The peak of absorption tends to shift to the lower frequency region when the air gap thickness is increased.