Ever increasing demands for NVH related comfort have substantially reduced the exterior and interior noise of automobiles worldwide. This involves identification of the noise sources, paths of vibro-acoustic transfer paths and their reduction measures. Many a time, NVH is looked at after the product has been designed and even prototypes have been fabricated. The major source of noise in a vehicle is the driveline. Any changes in the driveline for noise optimization affect the performance as well as exhaust emissions of the vehicle. This makes the changes for improvement of NVH limited. One of the important criteria for the marketability of the vehicle is NVH. Hence, lot of development work is going on for noise reduction. The diesel engine plays a vital role in automobiles and agricultural equipments in the Indian scenario due to economic considerations. This paper presents comparison of noise assessments of diesel engines for five different applications viz. 3-wheeler, passenger car, Multi Utility Vehicle (MUV), Heavy Commercial Vehicle (HCV) and Agricultural Tractor (AT), which are the major modes of transportation in India. It also describes the major noise contributors and methodologies for NVH refinements with case studies.