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With the stringent legislative requirements for noise in automobiles, gensets etc., the concern for properly designed silencers for specific applications is increasing. Optimized design of silencer requires an integrated study of acoustical and engine performance viz. Insertion loss and backpressure. However, the insertion loss itself depends upon engine characteristics geometry indicated by the transmission loss, flow induced noise, type of silencer - reactive, absorptive, hybrid, etc. Most of the work till date covers the acoustical and engine performance in isolation rather than in an integrated fashion due to the multidisciplinary nature of the problem. The objective of this study is to develop an integrated methodology to predict the performance of the silencer at the design stage resulting in an optimized time and cost effective design. In the present study, the acoustical and engine performance of silencer was predicted using FEM/BEM and CFD techniques.

The latest requirements for automotive cabin comfort require lower sound levels inside the cabin. There are many sources contributing to this noise of which fan is an important one. The blade passage noise of the cooling fan is often unpleasant and it is generally expensive to build and test different prototypes for optimum noise performance. Also, traditional unsteady computational approaches for predicting the fan noise are time and resource consuming and do not fit within the design cycle time. This paper proposes use of a steady state computational technique to predict the fan noise performance which provides for effective design study with optimum resources. The steady state data is used with the wave analogy to predict the overall sound pressure level. First, the computational results were validated with the experimental data for a base case and then parametric study was carried out to have optimum design.

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.

The acceptance criterion of any vehicle in terms of user comfort invariably depends on the vehicle interior noise and vibration characteristics. The levels of sound energy and structural excitation inside the vehicle compartment measures the amount of annoyance in terms of quality and comfort. For vehicle interior noise abatement and noise treatment, it is desirable to quantify the noise sources by determining the sound power contribution from each vehicle component/panel, acoustic leakages inside the vehicle, body panel vibrations, gearshift lever and steering wheel vibrations. Many a times, it is necessary to arrive at benchmarks or targets for the various sources of noise in order to refine the systems. The present paper describes a methodology for interior noise source identification and its analysis for benchmarking. Two different vehicles of the same class but of different makes were compared and evaluated for interior noise and vibration levels.