Countermeasures for Low Frequency Boom Noise Reduction in Electric Vehicle

Abstract

<div class="section abstract"><div class="htmlview paragraph">Electric vehicles (EV) are much quieter than IC engine powered vehicles due to less mechanical components and absence of combustion. The lower cabin noise in electric vehicles make customers sensitive to even small noise disturbances in vehicle. Road boom noise is one of such major concerns to which the customers are sensitive in electric vehicles.</div><div class="htmlview paragraph">The test vehicle is a front wheel driven compact SUV powered by electric motor. On normal plain road, noise levels are acceptable but when the vehicle has been driven on coarse road, the boom noise is perceived, and the levels are objectionable. Multi reference Transfer Path Analysis (MTPA) is conducted to identify the path through which maximum forces are entering the body. Based on MTPA, modifications are proposed on the suspension bushes and the noise levels were assessed. Operational Deflection Shape (ODS) analysis is conducted on entire vehicle components like suspension links, sub frame, floor, roof, and doors to identify the deflection pattern of the components at frequencies where the noise levels are higher. Based on full vehicle ODS, the critical components with maximum deflection at problematic frequency is identified and modifications are proposed to increase the dynamic stiffness of the components to reduce the noise levels. Effect of increase in stiffness of each critical component on cabin noise has been discussed. Alternative solutions like tuned mass dampers at the anti-nodal point are also explored and the changes required on the parameters of the damper to improve its performance is also discussed. With all modifications, the low frequency booming noise is reduced by ~ 4 dB (A) and the levels are acceptable. Design criteria that should be considered for vehicle components in early phase of development to avoid this concern are elaborated.</div></div>