In-situ measurement method of sound transmission loss under an oblique incidence of plane wave

In this study, two-dimensional finite-difference time-domain analysis was used to investigate sound transmission loss (STL) of porous materials with different incident angles. This method has provided evidence for the feasibility of measuring STL in situ using one particle velocity–pressure sensor and one pressure sensor. In the numerical analysis, the total sound pressure and the vertical component of the total particle velocity at the incident side of the material were used to separate incident and reflected components. The STL was calculated using the separated sound pressure at the incident side and the sound pressure at the transmitted side of the porous material. The STL calculated from simulation agrees with theoretical values at all incident angles investigated.