Experimental Acoustic Measurements in Far Field and Near Field Conditions: Characterization of a Beauty Engine Cover

Present work focuses on experimental acoustic characterization of an engine beauty cover in far field and near field conditions. Specifically, a comparison between results coming from the two different experimental measurement techniques is presented. Experimental campaign has been carried out on a car engine compartment at different operating conditions, by using on one hand a typical pressure microphone for far field measurements accordingly the related prescribed standards, and on the other hand the more innovative Microflown p-u intensity probe (pressure – particle velocity sensor) for near field measurements. In the latter case, experimental tests have been conducted adopting the Scan & Paint method, based on the acquisition of sound pressure and particle velocity by manually moving the probe across the sound field whilst filming the event with a camera. Differently obtained results have been then analyzed highlighting the peculiarities of each of the two techniques. Finally, evaluating noise emissions with and without cover presence, it has been possible to verify the acoustic performances of the component, identifying a less performing acoustic behavior of the material at some specific frequencies. Hence, future developments could regard the possibility to implement an optimization process through the analysis of different materials and configurations, in order to improve cover acoustic insulation properties at the frequencies of interests.