Haul truck sound power assessment

Part of the noise impact assessment (NIA) process of current or proposed open cut mines involves predictive noise modelling of mining scenarios to determine an area of affectation. Crucial to predictive noise modelling is accurate sound power level data of the mobile mining equipment to be utilised. ISO [1-3] (International Organisation for Standardisation) and AS [4] (Australian Standard) documents, along with industry developed methodologies, exist for this task and should be utilised when determining equipment sound power levels to be used in NIA modelling, and, determining compliance of equipment eventually used in production with sound power limits extracted from the NIA process. However, these standards and methodologies are often not employed, or are so reduced in scope and detail, that the resultant data is of questionable value and use. Use of questionable methodologies and resultant sound power level data has, in the authors' experience, lead to incorrect model results, sound power specifications not suitable for the intended mine, determination of an incorrect noise affectation area, and, ultimately, significant cost to the mine. Haul trucks are generally the most numerous plant type on a mine site and, as such, accurate determination of haul truck sound power is vital. Two levels of haul truck sound power assessment are presented (compliance and screening) and critical variables for each level of assessment are highlighted and discussed. Results from each level of assessment are compared, showing an agreement between the two methodologies of less than 2 dB/dB(A) (absolute). A theoretical exercise is also undertaken to highlight the effect on results of reducing the number of microphone positions used in determining compliance sound power.