Studies on the sound absorption coefficient-temperature-frequency relationship on polymer

The sound absorption coefficients of polyethyl methylacrylate(PEMA) and pol yvinyl chloride (PVC) were investigated by means of the impedance tube tech nique. The results showed that the sound absorption coefficient of the mate rials exhibited a higher value in its glass transition region due to the mo re sound energy lost by converting it into the heat energy. Moreover, the f urther studies discovered that PEMA and PVC possess the characteristic soun d absorption frequencies. When the PEMA and PVC were in their glass transit ion region, the number of their characteristic absorption peaks increased. The phenomena can be partly explained from free volume theory. The diagrams on the three-dimensional relationship of sound absorption coefficient-temp erature-frequency for PEMA and PVC were obtained which were of important si gnificance in the application of noise reduction.