Measurement of Transfer Matrices of Polyurethane Foam Materials for Sound Absorption and Transmission Loss Applications

The chemistry of polyurethane flexible foam enables its use in a wide range of sound absorption, sound transmission loss and vibration damping automotive applications. A challenge for developing new acoustic materials is to have a reliable, reproducible and representative small-scale measurement technique to obtain acoustic properties of polyurethane foam. In this paper we present a new measurement technique, based on an impedance tube, where the four pole parameters, or transfer matrices, can be obtained for these materials. A library of transfer matrices for various polyurethane foam materials is obtained and absorption, reflection and transmission coefficients calculated. The materials may also be combined in various layered assemblies. Furthermore, the meaning of the transfer matrix is explored with respect to previous studies on polyurethane foam microstructures.