Vibro-acoustic Study of a Full Vehicle Excited by an Electric Motor: Structure-borne and Air-borne Noise Comparison

This paper presents a workflow that allows noise, vibration and harshness (NVH) engineers to objectively predict the passenger compartment noise levels due to structure-borne and radiated noise arising from the motor of an electric powertrain (ePowertrain). The optimized simulation workflow enables transmission, vehicle design engineers and NVH analyst to collaborate and address potential noise concerns well before production of the ePowertrain unit and vehicle. The NVH targets can be cascaded through a series of transfer functions, linking the electromagnetic (EM) excitation from the motor to passenger compartment noise level requirements. The workflow involves the use of Romax Spectrum and Actran software. The structural modelling of the ePowertrain including the vibration response of the ePowertrain is calculated using Romax Spectrum, whilst Actran computes the acoustic radiation around the complete vehicle, and Virtual SEA then covers the calculation to interior and exterior vehicle noise analysis. The former enables early NVH diagnostics and optimization of the ePowertrain system. The Actran Virtual SEA approach is used to extend the frequency range of an existing full-vehicle Finite Element (FE) model. It offers the advantage to evaluate on the same model, both the structure-borne and air-borne noise inside the cabin and assess their relative impact. This is an innovative approach compared to past methods used for evaluating the NVH performance of ICE vehicles where FE models were used for low-frequency structure-borne noise and Statistical Energy Analysis (SEA) models for high-frequency air-borne noise. This separation is not anymore possible and reliable high frequency methods for structure-borne noise are now mandatory.