Prediction of acoustic transmission in heavily damped system using hybrid Ray-Tracing-SEA method

Classic statistical energy analysis mainly deals with the energy transmission of system with relatively low damping. With the application of passive damping treatments, one of the fundamental assumptions in SEA, i.e., a diffused field, tends to fail. The energy attenuation along transmission path becomes so significant that there may exist large energy level difference within one structural component. In light of this, this study proposes to use a hybrid ray-tracing-SEA method to predict the acoustic transmission in heavily damped system. Heavily damped structural components are treated as "coupling elements" instead of normal "subsystems." The energy transmission from one structural element to a connected structural element through the edge can be represented by using certain number of point sources and assuming each point source radiates certain number of acoustic rays. By tracing the travelling history of each ray, the energy attenuation along the travelling path can be achieved. With the information of energy input and energy attenuation, the equivalent coupling loss factors can be computed. By rebuilding a hybrid raytracing-SEA model, the energy level differences between different subsystems can be determined. Numerical validation of the ray tracing algorithm is conducted by comparing the calculated coupling loss factor with normal SEA method. Numerical study of a one-room system is given. The room is assumed to consist of six homogeneous concrete plates and the analysis assumes no coupling between in-plan and outplane waves. Comparisons between classic and hybrid method show that when a small number of the structural components are heavily damped, classic SEA gives similar results with the hybrid method because the prediction errors tend to cancel with each other and the transmission is dominated by paths that are not damped. With the increasing number of damped elements, SEA tends to underestimate the energy level difference. (C) 2020 Institute of Noise Control Engineering.