Reduction of Vehicle Noise by Modifying the Stiffness of Joint Parts by Applying a Substructuring Method

Abstract

This study aims to change and improve the transmitted force to the vehicle body, the Noise Transfer Function (NTF), and vehicle interior noise by modifying the stiffness of joint parts, which are the local areas of the subframe and body in white (BIW) connected to isolators. We adopted frequency response function (FRF)-based substructuring in order to understand the effects of the stiffness of joint parts for reducing the vibration in the transfer path of a ‘chassis-isolator-vehicle body.’ In addition, a process that could be used to predict and reduce the vehicle interior noise was developed based on FRF-based substructuring. Using the FRF-based substructuring technique, the transmitted force from the chassis to the vehicle body caused by the increased stiffness of the joint parts in the chassis and vehicle body was calculated. Subsequently, the NTF from the joint parts of a vehicle body to the driver’s ear location was calculated. In the chassis, the transmitted force to the vehicle body increased with increasing stiffness of the joint parts of the chassis. For this reason, the vehicle interior noise increased. In the vehicle body, the transmitted force to the vehicle body increased when the stiffness of the joint parts of the BIW was increased. But, as the noise transfer function was reduced the vehicle interior noise decreased. In the case where the stiffness of the isolator was smaller than that of the joint parts in the vehicle body and chassis connected to the isolators, the transmitted force to the vehicle body did not increase. In conclusion, a reduction of the vehicle interior noise was caused by reduced vibration when applying a low stiffness for the isolators (or bush) and a high stiffness for the joint parts.