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A method is presented to evaluate diesel engine structure borne noise differences caused by component design changes of the engine assembly. A flexible multi-body dynamics model is used to develop loads on the engine due to combustion, piston-liner interactions, and interactions at the main bearings. These loads are applied to an engine finite element model for frequency response analysis. The frequency response analysis is then varied by changing the component design of the engine assembly. Surface velocities and modal participation factors are determined from the frequency response. The participation factors are then used in a modal acoustic transfer analysis to compute the sound power. Comparisons are made between assemblies and to experimental data.

An approach is presented here to analyze and quantify individual partial noise sources and their contribution to the overall pass-by SPL of a medium duty diesel truck. Navistar, Inc. and Pelzer Consult GmbH have developed and successfully verified this method on one of their current production International DuraStar model medium duty trucks. First the operational sound powers of all relevant noise sources were extracted with near field SPL measurements under real pass-by test run conditions. Second, the Spatial Transfer Path Analysis (TPA) from all individual noise sources to the receiver microphones under different view angles was measured. Finally each single contribution was calculated and summed up to the overall virtual pass-by SPL. This virtual SPL is in close agreement with the measured values. The output of such investigations was a near and far field sound power and contribution ranking which results in an improved accuracy applying sound treatments.