Double Spherical Array for Vehicle Acoustic Optimization

Identification and characterization of interior noise sources have become a necessary step in automotive industry to improve acoustic comfort. For several years, MicrodB have developed a well-suited tool for interior noise localization based on a spherical rigid array. To further improve result obtained in low frequencies, a solution developed by MicrodB consists in adding extensions with microphones on the rigid spherical array to create an open spherical array with a larger diameter. This double layer spherical array associated with multi-array processing, based on beamforming techniques, combines advantages of the open sphere, mainly its good spatial resolution and dynamic in low frequencies, and the rigid sphere, its good directivity allowing localization in reverberant conditions. The main advantage of this measurement technique is the ability to characterize simultaneously the whole vehicle cabin in very short measurement duration and to do “on the spot” analysis of the measurement thanks to fast localization processing. It is thus a very attractive solution for use in costly test conditions, such as for example wind tunnel tests, but also road noise and trim optimization.
In this paper, application cases of acoustic comfort optimization of vehicles will be presented: aero-acoustic excitation of a car in a wind tunnel and standard running configurations for a bus. Although the running configurations differ in those two cases, approach and goal are similar: Identify radiating parts or insulation weakness of vehicles and estimate influence and gain obtained with tested solutions.