Catholic churches, sound-reinforcement systems and RASTI

Abstract

This paper concentrates on the Rapid Speech Transmission Index (RASTI) values within churches and on their differences with the sound-reinforcement systems (SRS) off and on. The RASTI was measured in 31 unoccupied Portuguese Catholic churches built in the last 11 centuries. Four receiver locations were used in each church, with and without the use of the SRS from the altar area. The vast majority of churches tested with the SRS off have RASTI values not greater than 0.45 giving a poor rating in the quality of speech intelligibility. It was detected that only for distances greater than about 11 m from the altar area is the SRS useful in increasing the RASTI values. In general, the standard SRS systems used in Portuguese churches induce an average increase of 7 per cent in the RASTI values if considering all receiver positions. Excluding the closest position to the sound source, the average increase of the RASTI is about 19 per cent from the RASTI values measured with the SRS off.