The effect of Pulpits in the RASTI values within churches

Abstract

This paper concentrates on the Rapid Speech Transmission Index (RASTI) values within churches with the use of elevated lateral pulpits for the emitting location. The RASTI was measured in 19 Catholic churches in Portugal built in the last 9 centuries. Four receiver and two source locations (altar and pulpit) were used in each church, without the use of sound reinforcement systems. The pulpits occupied a central (lateral) position in the churches' nave and at an average height of 2.3 m.The mean RASTI values in each church varied from 0.23 to 0.56 (of the altar) and from 0.32 to 0.56 (of the pulpit). Analysis of all RASTI data shows that the use of pulpits increases an average of 6% on RASTI values within churches. The variation in the RASTI values regarding the use of the pulpit over the altar as the source location, changed from -0.46 to +0.21 depending strongly on the receiver relative position to the sound source. Only for the receiver positions in the central area of the church does the pulpit position increase the RASTI (an average of 20% or about 0.07 on their absolute values). The churches' front row positions (closest to the altar) have their RASTI decreased (an average of 18% or about 0.13 on their absolute values) when the sound source is on the pulpit. On the last row positions RASTI does not change significantly (on average).