Sinclair Knight Merz was contracted to measure and rank the external noise sources on a Dash 9 series locomotive for the National Rail Corporation. The aim of the project was to confirm the dominant source of noise and to provide design data for future locomotives. A comprehensive test program was developed in conjunction with General Electric to identify the complex interaction of airborne and structure-borne noise sources associated with the main engine and auxiliary equipment on the locomotive.
Initial tests quickly confirmed that the dominant source of noise was the exhaust discharge. The firm subsequently designed and fabricated a duct to direct the exhaust noise away from the measurement side of the vehicle. This allowed the remaining noise sources, including various fans, a turbocharger and V16 diesel engine, to be identified and ranked using sound intensity techniques.
This relative ranking of all sources contributing to wayside noise was obtained for all loads and speeds such that noise reduction targets could be specified for both “A”-weighted and low frequency “Linear” noise emissions.
This valuable information was used as design input to optimise the acoustic and weight performance of noise control treatments for the next generation of locomotives.