This thesis concentrates on the effect of structural vibration on the internal noise level of vehicle, named structure born noise, as a part of NVH analysis. There is a daily demand increase for ride comfort in car manufacturing industries. The development of lighter and more fuel-efficient automobiles, make vehicles susceptible to low frequency vibration and noise, so uncomfortability is now a new concern in modern products. A pre-production NVH analysis is the key for achieving a proper ride comfort. Predicting the acoustic response of the interior cavity in different frequencies and proper use of noise control methods such as passive and active noise control plays an important role in this case. In this dissertation vibrational and acoustic simulations are performed on a three dimensional structure and internal space cavity of a pickup truck. Uncoupled method has been employed and so the analysis divided into two separated parts; structural analysis and acoustic analysis. Structural analysis begins with modal analysis to determine the behavior of the structure. Then the structure response due to power plant and road excitations has been calculated. Vibrational analysis is performed by considering all of the effective components and vibrational tracks in the cabin and the resultant internal noise. Also effect of natural frequencies on the acoustic level is discussed. Then acoustic simulation of the internal space of the cabin is done and the noise levels due to structural responses are calculated for the standard point of driver’s right ear. In this part, the mode shapes of the cavity are determined and are used for analyzing the structural and acoustic resonant couples. These normal modes also used to predict the acoustic behavior of the cavity in different frequencies. Finally, the simulation results are used to reduce noise through passive noise control methods.
