Empirical prediction of the effect of classroom design on verbal-communication quality

Abstract

This study used empirical prediction models to investigate how verbal-communication quality in 'small', 'medium' and 'large' classrooms varies with classroom design, and identified the optimal designs. Verbal-communication quality was quantified by the room-average speech intelligibility. The design parameters studied were the occupancy, the unoccupied background-noise level, and whether or not the rooms were carpeted, had ceiling and/or wall absorption, or upholstered seats. The design parameters were varied, and the following quantities calculated: average classroom surface-absorption coefficient at 1 kHz, 1-kHz early-decay time, A-weighted background-noise level, and A-weighted speech-signal to background-noise level difference. The conditions under which optimal verbal-communication quality occurred were identified. Quality did not vary with absorption or early-decay time in any systematic way. High background noise, combined with either high absorption or low early-decay time, can lead to very low verbal-communication quality. Quality was low for negative values of signal-to-noise level, but increased quickly for higher values. In the 'small' and 'medium' classrooms, the optimal verbal-communication quality occurred with carpeting and absorption, and with un-upholstered seats. In the 'large' classroom, the optimal quality occurred with carpeting, absorption and upholstered seats. The most significant design factor in determining the verbal-communication quality of the rooms was the background noise.