One of the major concerns in the vehicle trim part design is the acoustic targets, which are generally defined by absorption area or coefficients, and sound transmission loss (STL) or sound insertion loss (SIL). The breaking down of acoustic targets in vehicle design, which is generally referred to as cascading, is the process of determining the trim part acoustic targets so as to satisfy full vehicle acoustic performance. In many cases, these targets are determined by experience or by subjective evaluation. Simulation based transfer path analysis (TPA), which traces the energy flow from source, through a set of paths to a given receiver, provides a systematic solution of this problem. Guided by TPA, this paper proposes a component level target setting approach that is based on the statistical energy analysis (SEA), an efficient method for vehicle NVH analysis in mid and high frequencies. Using a validated SEA model of the vehicle under consideration, the contributions of common noise sources and paths, which are generally defined on parts of sheet-metal with trim parts attached, can be evaluated. This allows the prediction of interior noise level due to various possible sound packages. On the base of this, acoustic target setting of trim parts can be defined as the solution of a mathematical optimization problem. The targets such as SIL of trim parts at certain frequency range are taken as design variables, and the vehicle level performance like the sound pressure level (SPL) at driver’s ear is incorporated into constraint functions. This approach is versatile and is suitable for traditional ICE vehicles and modern EVs. It can be used on a vehicle prototype at the early stages for target cascading, or on an existing vehicle model for NVH improvement. Several cases and examples on this target setting method have been discussed in the paper.
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