A Source-Transfer-Receiver Approach to NVH Engineering of Hybrid/Electric Vehicles 2012-36-0646

Vehicles with electrified powertrains are being introduced at an increasing pace. On the level of interior sound, one is often inclined to assume that NVH problems in EV have disappeared together with the combustion engine. Three observations demonstrate that this is not the case. First of all, only the dominant engine sound disappears, not the noise from tire, wind or auxiliaries, which consequently become increasingly audible due to the removal of the broadband engine masking sound. Secondly, new noise sources like tonal sounds from the electro-mechanical drive systems emerge and often have, despite their low overall noise levels, a high annoyance rating. Thirdly, the fact that engine/exhaust sounds are often used to contribute to the “character” of the vehicle leads to an open question how to realize an appealing brand sound with EV. Hybrid vehicles are furthermore characterized by mode-switching effects, with impact on both continuity feeling and sound consistency problems. Their acoustic design will henceforth remain a challenge, though with different targets, different electro-mechanical solutions and requiring new/alternative simulation and testing approaches. The paper addresses some of the major elements in this Electric/Hybrid NVH engineering process following a source-system-receiver approach. A detailed discussion of each of these steps is complemented with 4 case studies covering electric motor noise simulation, power electronics, lightweight body design impact and vehicle warning sound.