The effects of ceiling height and absorber placement on speech intelligibility in simulated restaurants

Abstract

The intelligibility of speech was measured in simulated rooms with parametrically manipulated acoustic features. The rectangular rooms were designed to simulate restaurant environments with either three or nine occupied tables, using either speech or noise as interfering sounds. The existence of more detailed acoustic features, such as furniture was also modelled. The measurements revealed that reverberation time was poorly correlated with speech intelligibility. In contrast, a psychoacoustic model of spatial release from masking produced accurate predictions for noise interferers and ordinally correct predictions for speech interferers. It was found that rooms with high ceilings facilitated higher speech intelligibility than rooms with lower ceilings and that acoustic treatment of walls facilitated higher speech intelligibility than equivalent treatment of ceilings. Ground-level acoustic clutter, formed by furniture and the presence of other diners had a substantial beneficial effect. Where acoustic treatment was limited to the ceiling, it was found that continuous acoustic ceilings were more effective than suspended panels, and that the panels were more effective if acoustically absorbent on both sides. The results suggest that the most effective control of reverberation for the purpose of speech intelligibility is provided by absorbers placed vertically and close to the diners.