Experimental and theoretical basic research on sound absorption characteristics of foam materials with and without membrane

Abstract

A basic study was conducted to theoretically estimate the acoustic properties of a sound-absorbing foam material. Generally, the lattice of sound-absorbing foam materials contains membranes. Herein, for simplicity, a mathematical model was constructed assuming a cubic frame structure as the basic frame structure of the foam, which included a membrane. Accordingly, the sound absorption coefficient was obtained and compared with the experimental results. In the mathematical model, the clearance in the frame structure (with membrane) was divided into elements and was approximated as a clearance surrounded by two parallel planes, considering the exact shape of each element. Herein, the characteristic impedance and propagation constant of the approximated clearance were obtained and treated as a one-dimensional transfer matrix, and the sound absorption coefficient was calculated using the transfer matrix method. For the experiments, the samples were fabricated using a 3D printer and the sound absorption coefficient was measured using a two-microphone impedance tube. Overall, the experimental and theoretical results exhibited similar trends.