BEM & FEM-IFEM modeling and analysis methods for high complexity vehicle models

The relevance of simulation methods for the assessment and the analysis of exterior noise in the automotive and truck industry is likely to increase in the fore-coming years, due to the announced revision of the ISO 362 regulation as well as to the strong increase in the variety of options offered to automotive and truck OEMs. That, in particular, for what concerns the definition of the sound package in the engine bay, that forces them to look with interest at methodologies that allow making concept decisions (e.g. which concept to use for an absorber or where to put the shields under a truck's cabin) already in the design phase. This article describes a numerical/experimental activity aimed at comparing the performance of two deterministic simulation methods, namely the Boundary Elements (BE) method and the Automatically Matched Layer (AML) method. The objective of the simulations consists in evaluating the exterior Acoustic Transfer Functions of a simplified (but not trivial) vehicle engine bay mock-up in a broad frequency range up to 3.5 kHz. The capabilities of the analysis methods of well representing the effect of both acoustic trim parts and apertures positioning around the engine bay has been checked. The methods' computational efficiency has been evaluated and compared in detail, as well as the accuracy of the results, by correlating with experimental data.