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In order to reduce the interior noise of a vehicle with a four-cylinder engine, investigations were made using finite element and vector methods, acoustic intensity testing and holography technique. The investigation resulted in inclination of the engine mounting, design changes to the front suspension member, a shock absorber engine mounting, structural modifications to reduce body panel vibration and a new engine mounting to insulate high frequency engine vibration.

The booming noise in passenger cars particularly with four cylinder engine is often caused by exciting forces transmitted from the engine to the body structure through front engine mountings. Vector analysis to investigate the relation between these transmitted forces and the sound pressure in the cabin is introduced, some examples of reducing the booming noise by modification of engine front mountings are shown and the points to be considered in the design of engine mountings are mentioned in the paper.