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In today's competitive automobile marketplace with reduced vehicle development time and fewer prototypes/tests, CAE is playing very crucial role in vehicle development. Automobile environment demands ever improving levels of vehicle refinement. Performance and refinement are the key factors which can influence the market acceptance of vehicle. Driveline is one of the key systems whose refinement plays critical role in improved customer satisfaction. Because of the virtue of the driveline functionality, driveline induced noise and vibration are the most common issues in the AWD vehicle development programs. Refinement of the drive line needs complicated nonlinear full vehicle CAE MBD models for the evaluation of driveline induced noise and vibration responses at different operating conditions [1]. In this paper a simplified approach is adapted for solving the Noise & Vibration issue which has been identified at the prototype testing level of an AWD vehicle development.

Wind noise is becoming important for automotive development due to significant reductions in road and engine noise. This aerodynamic noise is dominant at highway speeds and contributes towards higher frequency noise (>250Hz). In automotive industry accurate prediction and control of noise sources results in improved customer satisfaction. The aerodynamic noise prediction and vehicle component design optimization is generally executed through very expensive wind tunnel testing. Even with the recent advances in the computational power, predicting the flow induced noise sources is still a challenging and computationally expensive problem. A typical case of fluid-solid interaction at higher speeds results into broadband noise and it is inherently an unsteady phenomenon. To capture such a broad range of frequency, Detached Eddy Simulation (DES) has been proven to be the most practical and fairly accurate technique as sighted in literature.

One of the primary excitation sources in a passenger car comes from the powertrain [1]. Refinement of powertrain induced noise is the most critical tasks during a vehicle refinement. Due to ever increasing demand for reduced design and development cycle, most critical decisions have to be made at the concept stage. Powertrain radiated noise is one of the most important performance factor that must be evaluated during the concept stage. Solution time for calculating the radiated noise using the existing acoustic solvers is very high and requires very expensive resources like software and hardware. Arriving the optimal design with conventional method is very tedious job. A new method has been adopted for identifying the critical areas and coming up with the optimal design modifications within a short span of time. Powertrain radiated noise has been calculated with the help of acoustic solver.

Idle NVH (Noise Vibration Harshness) is one of the major quality parameters that customer looks into while buying the vehicle. Idle shake is undesirable vibrations generated from Engine while it is in idling condition. These low frequency vibrations affects both driver and passenger comfort. Vibrations are perceived by customer through the interfaces such as the seats, floor, and steering wheel. The frequencies of vibration felt by customer ranges between 10-30 Hz and varies based on engine configurations. There are two factors that are critical to the vehicle idle NVH quality, 1. Engine excitation force and 2. Vehicle sensitivity to excitation forces (Transfer function). Even though the engine excitation forces are governed by cylinder combustion process inside the cylinder and engine mass, it is also largely affected by how well the engine and transmission are supported on vehicle through isolators.

In a scenario where cost and weight targets are becoming critical, we tend to produce lighter and more powerful vehicles. In this context, NVH becomes one of crucial parameters in overall performance delivery. Other than power train, road induced noise also becomes an important parameter within vehicle development. Predecessor vehicle is body over frame structure and here a monocoque vehicle is considered for study. Different techniques like transfer path analysis, vibro-acoustic modal analysis, operational deflection shapes are used to identify the major force paths, radiating panels and their sensitivity to noise at operator ear location. Simulation model of body is built with good correlation and input forces are given at different attachment points to predict the noise levels. This combined approach helped us in reducing the overall noise level at certain constant speed by 4 dB(A) and also with great ease. All recommendations from this exercise are implemented