Sound quality analysis of the powertrain booming noise in a Diesel passenger car

Among many noises which can be heard inside a car, the booming noise caused by powertrain excitation is usually considered as one of the very annoying acoustic features that affect the interior sound quality of a car. This work presents results coming from an experimental analysis carried out on a Diesel passenger car in order to evaluate the interior booming sensation related with the engine rotation and firing. Tests were performed in acceleration conditions on the vehicle installed at the chassis dynamometer, by measuring noise at the driver and passengers' positions inside cabin. A waterfall analysis was firstly carried out to see the spectral and temporal pattern of recorded time-varying sounds. In particular, the change of sound level related to the fundamental frequency of engine firing and its harmonics was assessed as a function of engine revolution per minute at each microphone location. Acquired data were properly post-processed for sound quality analysis as well, in order to have information about the degree of booming sensation in the accelerating car and to quantify the level of annoyance perceived by each car's occupant. The analysis allowed to identify the vehicle operating conditions as well as the locations inside cabin that make the passengers more exposed to the booming phenomenon. The obtained results represent a useful starting basis for selecting the most appropriate noise and vibration control strategies in vehicle sound quality optimization process.