Improving speech intelligibility in reverberant rooms

Abstract

Speech intelligibility in rooms with long reverberation times has long been a problem for acousticians. This problem is exacerbated when the option for acoustic treatments is not an option for a variety of reasons. In this study, a constant-beamwidth, wide-bandwidth (CBWB) loudspeaker array was used to improve speech intelligibility in two multipurpose rooms where treatment was not an option. A CBWB loudspeaker array was designed with independent beam pattern control on both the horizontal and vertical axes. A wide horizontal beam pattern and narrow vertical pattern were designed to achieve constant coverage from 500 Hz to 4 kHz. The array incorporates four separate arrays, two with nested elements, and linear-phase FIR filters to maintain constant beamwidth over the three octaves of interest. Room simulations were conducted with CATT-Acoustic and the array was implemented and compared to a source with a more conventional coverage pattern. The STI method was used to measure speech intelligibility at several positions throughout the rooms. The study showed an improvement in speech intelligibility and a reduction in measured reverberation times.