A BEM study of the influence of musicians on onstage sound field measures in auditoria

Many recent studies have sought to assess the acoustical experience of musicians playing in ensembles through development of acoustic measures undertaken on stage in auditoria. It is generally proposed that such measures be undertaken in the presence of stage furniture to better replicate the real conditions onstage with an ensemble present. However, conditions are arguably not necessarily realistic because furniture is customarily removed within 2m radii of the source and receiver to avoid disturbing reflections, and because it is seldom practical to make the measurements with the musicians present. Furthermore, consistency of conditions is also potentially an issue. This paper uses BEM (boundary element method), validated against published full and model scale data, to investigate the differences between sound fields on a stage with an orchestra present and on a bare stage. Sensitivity to perturbations of the stage configuration is also investigated. The results of this study show that for a chamber orchestra, set up on stage, for 250 Hz and above the sound field on an occupied stage differs significantly from an empty stage.