Case History: Factory Noise Prediction Using Ray Tracing--Experimental Validation and the Effectiveness of Noise Control Measures
Murray R. Hodgson · Noise Control Engineering Journal · 1989
Factory-noise prediction models are invaluable in allowing worker noise-exposure levels in a factory to be evaluated prior to construction and, if necessary, for modifications to be made or noise-control measures to be evaluated. Ray- tracing techniques have proven to have the necessary accuracy and flexibility. In order to evaluate the accuracy of a ray-tracing model, comparisons were made between predicted and measured sound pressure levels for a machine shop with nine noise sources in operation. The shop was modeled using the known geometry, source and receiver positions, air absorption coefficients, and the measured source sound power levels. Surface absorption coefficients were chosen on the basis of reverberation time measurements in similar factories when empty. The machine shop fitting density and absorption coefficients were chosen on the basis of previous research and by comparing the predicted and measured sound propagation curves for the shop, varying the fitting density to obtain a best-fit agreement. The ray- tracing model proved to give excellent prediction accuracy. By comparison, predictions by the Eyring theory are shown to be less accurate. Finally, the usefulness and flexibility of the ray-tracing approach are demonstrated by predicting the effectiveness of possible noise control measures comprising acoustic screens and suspended absorption.