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Technical Paper

Tire and Car Contribution and Interaction to Low Frequency Interior Noise

A joint study was conducted between BMW and Goodyear with the objective of analysing the cause and identifying methods to reduce the structure-borne interior noise in a vehicle driving on rough road surfaces. A vibro-acoustic characterization of the car was performed by measuring the car vibro-acoustic transfer functions and by using a transfer path analysis technique to identify the main suspension parts affecting the interior noise at target frequencies. The vibration transmissibility characteristics of the tire were measured and also simulated by Finite Element in [1-200Hz] frequency range. The vibro-acoustic interaction between the tire and car sub-systems was examined. A Finite Element sensitivity analysis was used to define and build new prototype tires. A 3dB(A) interior noise improvement was obtained with these new tires at target frequencies.
Technical Paper

Comparison and Verification of Experimental and Numerical Models for the Prediction of the Efficiency of Engine Noise Shields

The reported investigations aimed at adopting and verifying numerical prediction methods for the determination of the efficiency of engine sound shields. An extended measurement series and parallel Boundary Element calculations were conducted on a simple engine simulator with various engine shields. The effect of the shields was expressed in terms of spatially averaged, narrow band Insertion Loss spectra. It was found that the efficiency of sound shields is determined by complex interactions between the source and its surroundings. These effects could be better understood and reasonably well predicted by using the BE method. The relative IL quantity can be calculated more accurately than the absolute sound field descriptors themselves.