Driveline Boom Interior Noise Prediction Based on Multi Body Simulation

It is important to develop powertrain NVH characteristics with the goal of ultimately influencing/improving the in-vehicle NVH behavior since this is what matters to the end customer. One development tool called dB(VINS) based on a process called Vehicle Interior Noise Simulation (VINS) is used for determining interior vehicle noise based on powertrain level measurements (mount vibration and radiated noise) in combination with standardized vehicle transfer functions. Although this method is not intended to replace a complete transfer path analysis and does not take any vehicle specific sensitivity into account, it allows for powertrain-induced interior vehicle noise assessments without having an actual test vehicle available. Such a technique allows for vehicle centric powertrain NVH development right from an early vehicle development stage. While this is a proven tool for powertrain level sound quality evaluations and correlates well for front wheel drive (FWD) vehicles, the interior noise for rear wheel drive (RWD) vehicles is often under-predicted on account of missing contributions from the driveline. RWD vehicles can have significant contributions through the rear axle mounting paths, especially for powertrains with manual transmissions or during lock up of the torque converter clutch with conventional automatic transmissions. Torsional vibrations are transmitted through the driveline, causing reaction forces at the rear axle, resulting in driveline boom. Resonances in the driveline system typically amplify the driveline boom excitation.

This publication extends the dB(VINS) approach for interior noise simulation by determining the driveline-induced noise of a RWD vehicle. The influence of the structureborne path and firing order related torsional vibration through the rear axle is demonstrated with a time domain transfer path process. Generic transfer functions for extension of the dB(VINS) process are developed in order to capture driveline noise share of RWD vehicles. In addition to vehicle measurements, a multi body simulation (MBS) model is generated and rear axle vibrations are calculated via MBS simulation of the vehicle driveline. The results are discussed in the context of driveline NVH integration and appropriate conclusions provided.