Ray-tracing modelling of noise in a food-packing hall

Abstract

By modelling workroom sound fields, the influence of building geometry, surface absorption, machine layout, sound power and directivity on noise at operator positions can be evaluated. This can be invaluable at the design stage of new projects or when assessing the most cost-effective approach to control noise in an existing installation. The approach adopted here is to predict the octave-band sound-propagation curves for a single noise source in the particular workroom using ray tracing. Curves are predicted for propagation in different directions within the building and for different acoustical treatments. They are approximated by one or two straight-line segments whose slope(s) are determined. A separate program is then used to compute the combined effect of all machine-noise sources in the workroom at positions on a 1-m grid, using the slope(s) and the applicable environmental correction factor. These techniques have been successfully applied to a number of major projects. Here, a case study is presented which illustrates a design-stage application to a new packing hall, which was modelled to evaluate the effects of increasing the ceiling absorption over all or part of the ceiling. The workroom is described and the predictions done are detailed. Also discussed are lessons learned with respect to workroom modelling.