1. INTRODUCTION
Transportation vehicles generate exterior turbulent flows featuring fluctuating quantities either convected by the local mean velocity (associated to turbulent or aerodynamic energy in the following) or propagating along any direction in space at the speed of sound (acoustic energy). At car driving speed above 100 kmlh, aerodynamic and acoustic wall pressure fluctuations on the vehicle both contribute to the interior noise. This because the vibroacoustic behaviour of solid structure like side windows acts like a wavenumber filter that strongly cut-out wave number associated to the turbulent energy. Thus, acoustic fluctuations produced by the flow must be known to predict interior car noise. Evaluation from wall pressure signals of this acoustic energy produced by a turbulent flow like a boundary layer (TBL) is still an issue as it could lay at least 20 dB below the turbulent energy. At a given frequency, aerodynamic and acoustic wave number ratio equals the Mach number which is about 0.1 in that particular case and this is used here to separate acoustic energy.