Prediction and Improvement of Structure-Borne and Airborne Whines of an Electric Vehicle for Virtual Development

Abstract

Many sources and paths cause interior cabin noise. Some noise from an electric vehicle is unique and different from a vehicle with an internal combustion engine. Especially, whine noise occurs due to the particular orders of the electromagnetic force of an electric motor and transmission gears, which is tonal and usually reaches high frequencies. This paper covers structure-borne (SB) and airborne (AB) aspects to estimate whine, and the difference between the two characteristics is distinguished. The focus lies mainly on the process of virtual vehicle development and application for performance improvement. First, to predict SB whine, an e-powertrain is modeled as a finite element model (FEM), and electromagnetic (EM) forces are calculated. A vehicle model is also modeled as an FEM, in which interior sound packages are carefully modeled as they play an important role in the medium-frequency region. The e-powertrain and vehicle models (being simulated separately) are combined to obtain cabin noise up to 1.5 kHz. Design studies show that the stiffness of mount insulators and the panel stiffness of the vehicle can be substantial design variables to reduce the SB whine. Second, the study highlights a simulation method to predict interior airborne whine up to 8 kHz by combining the FEMs of the e-powertrain and the vehicle’s exterior cavity with a statistical energy analysis (SEA) model of a vehicle. Path contribution can be identified by defining source strength and acoustic transfer function of airborne paths. Design modifications, including encapsulation of the e-powertrain, show this simulation process could be practically useful to reduce the airborne whine at high frequencies.