Numerical evaluation of low frequency sound propagation in two layered media

Abstract

This paper presents the simulation results of the infrasound sound energy transfer through various interfaces and discusses on the acoustic transparency of different media as a function of refraction index. Acoustic transparency is defined as the ratio of acoustic power radiated into the structure to the acoustic power emitted by a wave source. The effect of various surfaces on the transmission of infrasound has been studied by numerical simulation. To examine the transmitted homogeneous and inhomogeneous plane waves at the air - textile interface, we used MATLAB 2016 to calculate and plot the contributions of homogeneous and inhomogeneous plane waves as a function of frequency ranging from 3 to 5 Hz. Textiles (composed of natural or synthetic fibres) such as 100% cotton, 50% cotton – 50% flax, 100% wool (felt), nylon1 and nylon2 and flax showing various wave propagation properties were investigated. We found that almost the entire acoustic power passes through the interface of layered structure in the case of wool, cotton and flax, therefore the reflected power can be neglected. In the case of nylons, an amount of acoustic power ranging from 2% to 25% is reflected into air.