Comparison of different noise and vibration reduction measures on a cover for power electronics

Electric vehicles feature specific noise, vibration and harshness (NVH) challenges due to the lack of the acoustic masking of a combustion engine. The emitted airborne sound of the electric powertrain is one of the main challenges the industry faces right now. In particular, the cover of the power electronics compartment is often acoustically suspicious due to its thin walled, broad shape and its close installation to the electric engine, which is the main excitation source. For the NVH design of such covers, standard measures like alubutyl and bitumen reach their limit, motivating the application of novel techniques for noise and vibration reduction such as vibroacoustic metamaterials (VAMM) and acous-tic black holes (ABH). The presented research quantifies the potentials of such novel methods by comparing them to common state-of-the-art measures. A ref-erence cover is equipped with two different add-on VAMM and modified with a structurally integrated VAMM and an ABH. The structural dynamic behavior of the cover variants is evaluated experimentally in the lab and compared to the ones of a bare cover and a cover equipped with an alubutyl layer. Within the so-called stop band of the VAMM variants a large vibration reduction of more than 20 dB in comparison to a cover with alubutyl is achieved. The cover with integrated ABH leads to extensive damping while being lighter as the cover with an alubutyl layer. For a vehicle test under driving conditions, an add-on VAMM is selected and compared to a state-of-the-art cover regarding the cover’s vibrations and sound pressure level in the inside of the passenger compartment at the driver’s ears. Here, a reduction of tonal components of up to 11 dB is achieved for the sound pressure level within the passenger compartment.