Low-Frequency Noise Transfer Path Identification Study for Engine Sub-Frame Utilizing Numerical Simulation 2015-01-2361

Nowadays, by the introduction of significant advances in automotive industries, noise, vibration and harshness (NVH), in the position of the main comfort attribute, plays a crucial role in marketing and passenger satisfaction. In order to cope NVH problems, three main actions are taken by NVH engineers for reducing perceived level of noise in cabin: Noise reduction in sources, Noise path treatment and Noise control at receiver. Among these approaches, those pertain to modification of noise pass, through structure and air, to the cabin are more prevalent in automotive applications. Accordingly, identification of noise paths that dominantly contribute to sound and vibration transfer to cabin phenomenon should be dealt with importance. In practice, engine vibration transmitted through sub-frame attachments to body can induce high level of noise and vibration to the passenger cabin. In this research, at first stage, optimization of shell thicknesses for four main engine sub-frame components is performed to minimize noise transfer function at driver's ear positions. Taguchi methodology is chosen for this matter as a robust method which reduces number of simulations significantly. Then, transfer path identification is performed for the optimized engine sub-frame configuration with six attachment mounts to the body structure. For this aim, numerical simulation is utilized for virtual analyses. Finite element method is used to simulate cabin vibro-acoustic behavior of a B-segment sedan car exited by engine vibration. Resultantly, contribution of each attachment point in the transferred noise to driver's ear is identified through calculating sound pressure level at critical frequencies in the designated points of cabin cavity.