Component Noise Source Ranking of a Medium Duty Diesel Truck during Pass-by Testing

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. Using this information to make truck modifications has already led to very good development results in a short period of time.