Research on the reverberation absorption coefficient of material measured by underwater reverberation field method

In this article, an underwater reverberation time model of a rubber board is established. Then a theory formula of reverberation time T(r_m,λ_m) is given according to the energy relation of sound field in the reverberation chamber. r_m is the reflecting fraction and λ_m is the absorption fraction, when sound wave is injected to a rubber board. r_m and λ_m can be resolved base on the wave theory and boundary condition. In addition, r_m and λ_m are related to acoustic parameters of the rubber board. T(r_m,λ_m)computed by formula and reverberation time T₀ measured in underwater space without material are all taken to Eyring formula, thus reverberant absorption coefficient of measured material can be forecasted. The edge effect due to the material is avoided using this method. In the simulation results of reverberation time and sound absorption coefficient agree with fact ruler. In pool experiment, reverberation time was measured in two cases. One case is that there is only water in the experimental water area, and another case is that the sample is put in water. The measurement results of the pool show the reverberant time T(r_m,λ_m)with rubber board is shorter than the reverberant time T₀ without rubber board, since absorption rubber board accelerates the speed of reverberant attenuation. The reverberant time T(r_m,λ_m) by experiment agree with the theory result. The sample frequency characteristic of the reverberation absorption coefficient accords with theory result.