Efficient Methodology for Automotive Powertrain Acoustic Radiation Analysis

In automotive NVH, the noise generated by a powertrain is still one of the major noise sources especially at low and mid vehicle velocity. For this reason automotive OEMs are continuously focusing on methods to efficiently analyze this noise source. For this purpose, a well-established simulation methodology can provide results thoroughly, within a limited amount of time and with a reduced cost contrary to experiments which are involved in late design phases and are more expensive. This paper aims at presenting an approach to simulate efficiently the acoustic radiation from automotive components. With this aim in mind, the acoustic response of a realistic powertrain unit subjected to working conditions ranging from 1000 RPM to 4500 RPM is studied until 3000 Hz. Several radiating boundary conditions will be assessed in order to detect the most efficient set-up for this kind of problem and to extract the optimized modeling guidelines. Particularly, a comparison of both components Infinite Elements and Adaptive Perfectly Matched Layer, modeling the acoustic propagation in a semi-infinite field, is led. For each radiating condition, the computation performances are evaluated. To carry out this study, the radiated powers (overall and by part) as well as the Sound Pressure Level at specific microphones are used as output indicators. The latter are obtained through the norm ISO3744 using a normalized sphere of microphones or directly by the power evaluation on the radiating surfaces. Eventually, investigations on two solution approaches, the Direct Frequency Response and the Green analysis are led to detect the benefits and disadvantages from each of them.