Numerical study of acoustic transmission across heavily damped plate using hybrid Ray-Tracing-SEA method

Abstract

Energy transmission across lightly damped structures has been well studied including the approved success of statistical energy analysis in mid and high frequency bands. For heavily damped elements, the diffuse field theory, which is used in computing coupling loss factors, tends to fail. Energy attenuation with distance becomes more significant for such elements and hence the energy is less likely to be evenly distributed within those elements. A ray tracing algorithm is developed taking account of this phenomenon by tracking the travel history of a great number of discrete rays. The predicted transmitted energy is used in a modified statistical energy analysis model to calculate energy level difference between different subsystems. Numerical validation and comparison on a concrete five-plate system are conducted in both lightly damped and heavily damped cases. Both the classic and the hybrid models show good agreement for lightly damped system and differ for heavily damped system. The difference tends to become larger with increasing frequency and internal damping level. The parameter “effective length ratio” is proposed to describe the phenomena of energy concentration along the edge and as in indicator of whether the application of diffuse field theory is appropriate.

Fast statistical energy analysis modelling of periodic box-like structures

“…As the damping levels of structural elements increase, the basic SEA assumption of energy equipartition tends to fail. Previous studies have shown that in such cases, classic SEA tends to give unreliable results and needs modifications [13,14]. One way to overcome the induced problem is to modify the SEA model with equivalent CLF.…”

“…This requires a new naming system of the SEA model. In addition, as the damping level gets higher, the predicting results from classic SEA tend to be inaccurate [13,14] and refined SEA models need to be built. The proposed method is typically useful in such kind of study.…”

“…When the energy distribution within a structural element is no longer diffused, this element can no longer be seen as a subsystem. The authors proposed a hybrid Ray-Tracing-SEA method to investigate the acoustic transmission in a five-plate system and a one-room system [13,14]. The energy transmission across heavily-damped structural elements was computed with a forward ray-tracing method and represented using 'equivalent CLFs' .…”