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As North American truck manufactures have entered the global market it has become apparent that there are widely varying drive-by noise regulations required in various areas of the world. This paper will describe differences between various test procedures, track layouts, and required levels. Data will be presented showing vehicle results from various procedures, used to quantify differences in noise levels between a range of procedures. Countries were ranked from least restrictive to most restrictive based on test procedures and legal market requirements.

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.