This paper on "Powertrain as a Booming Structure-Borne Noise Source" was presented at the NAFEMS World Congress on The Evolution of Product Simulation From Established Methods to Virtual Testing & Prototyping - 24-28 April 2001, The Grand Hotel, Lake Como, Italy.

Summary

This article presents a process of analysis, comprehension and improvement of the powertrain as a source of booming noise through solid transfer path. The variables we study are vibrations measured at the interface points of the powertrain with the car body, that means not only at the mount brackets and torque connecting rod, but also at the wheel hubs. Thus, the flexibility of the powertrain is taken into account as well as the flexibility of the halfshafts. The frequency band of interest lies between 25 and 250 Hz, which is the «booming noise» frequency range. With reference to the vibrations problems typically encountered in the development of in-line 4 cylinders powertrains transversely laid-out in the vehicle, we suggest a parallel experimental and numerical approach that explains and models the phenomena observed. It is shown how these very simple models can be used to guide the design in the first phases of the powertrain development. Then, we present a detailed model (in particular using the finite element method) able to achieve the vibratory absolute levels with a rather good accuracy. This type of model seems adapted to the development in the ultimate phases of the powertrain development.