3D meshless FEM-BEM model for prediction of sound fields in cabins due to external sound disturbances

The Finite Element Method (FEM) and Boundary Element Method (BEM) are widely applied to predict the sound pressure level (SPL) in enclosed spaces for low frequency problems. However, a single method usually cannot fulfill the task for predicting the internal SPL in enclosures including objects in the interior due to external disturbances. Moreover, these methods have some disadvantages such as complex pre-processing, time-consuming and inevitable pollution effects. Based on these drawbacks, this paper attempts to combine the Meshless Method (MM), acoustical FEM and BEM into a hybrid method which can be applied to predict the SPL in an enclosed environment with external sound sources. Firstly, the hybrid theory for the acoustic problem and its implementation are illustrated. Next, numerical simulations and experiments are conducted to validate the peak value, SPL and computing efficiency using this method. Comparative results obtained from the proposed method, FEM and BEM using SYSNOISE are shown to be in agreement, and the proposed method is more efficient. Experimental results show that the average relative error of SPL in each location is less than 5.26 %. It is corroborated that the proposed method is applicable to the prediction of the internal SPL with the case of exterior sound sources existed.