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Greater customer awareness is driving the automotive industry to constantly look to innovate and ensure that greater time, efforts and considerable resources are spent in developing a better vehicle. As we move away from noisy vehicles, the differentiating parameter in vehicles is the perception of quality in the vehicle noise or sound. As the masking effect due to overall vehicle noise level abates, many low noise sources gain prominence, which directly influences the perception of noise refinement. Hence, the concept of vehicle interior noise is not only limited to lower noise levels but has also extended to better sound quality (SQ). SQ technique involves use of relevant parameters for quantifying a subjective quality into an objective quantity. This paper will look at parameters relevant to subjective perception of vehicle interior noise and consider a benchmarking methodology targeting vehicle sound quality.

Transfer Path Analysis (TPA) is an important tool used worldwide to identify noise and vibration sources in vehicle(s). A complete TPA can be performed on proto-type vehicle or a fully built vehicle but it is time consuming and resource sensitive. New advancements in TPA include combining both acoustic and structural loads from stationary response functions and actual noise/vibration during operating conditions. So it is becoming important to define a known set of frequency response functions in order to understand vehicle's operational behavior. In this paper, an attempt has been made to simulate vehicle cab from structural and acoustic viewpoint with the help of vibro-acoustic transfer functions. Vibro-acoustic modal parameters, vibration transfer functions (VTF) and Noise Transfer Functions (NTF) were predicted using FEA techniques. A set of experiments on a simple model was carried out to validate the predicted FE results.

Acoustic Holography is emerging as a powerful, high-resolution noise source localization technique in this decade. Compared to conventional sound intensity measurement, Acoustic Holography scores because of its ability to provide on-line visualization of acoustic energy distribution of the sources perform measurements during stationary and transient conditions and it is substantially faster and easier. Further, with Near Field Acoustic Holography (NAH) and Beam-Forming (BF) techniques, it is possible to cover wide range of frequencies with reasonable investment. This paper compares and evaluates the advantages of the Acoustic Holography technique with conventional Sound Intensity Mapping for different applications such as noise mapping of a vehicle, noise source identification of engine and other small sized components. It also discusses how this technique can be extended to moving sources such as noise source identification during pass-by.