Hearing a Sacred Space: An Archaeoacoustic Analysis of the Church of St. Francis in Pula, Croatia

The Church of St. Francis in Pula, Croatia, is a well-preserved example of Franciscan gothic sacral architecture from the late 13th century. As preaching was highly valued by the Franciscan order as a way of communicating with the faithful, the study is focused on determining whether speech intelligibility in the church would have been adequate for successful communication between priests and their audience. The archaeoacoustic analysis of the church was performed in four stages: (1) in situ acoustic measurements in the present state, (2) development and calibration of the model of the present state based on measurement results, (3) development of the two models of the presumed historical state based on the calibrated model and historical data, and (4) prediction of acoustic conditions in the present and the historical states in terms of reverberation time T30 and of speech intelligibility in terms of speech transmission index STI. The factors considered in the study were (1) acoustics of the church, (2) profile of the audience (friars and the faithful), (3) layout of the audience areas (choir area in the front of the nave for the friars, back area of the nave for the faithful), (4) positions of the speech sources (altar for addressing the friars, pulpit for addressing the faithful), (5) occupancy (unoccupied and fully occupied church), (6) language used in liturgical ceremonies (Latin and native language), and (7) language proficiency of the audience (native speakers, users of a second language). The results show that (1) fair speech intelligibility (STI ≥ 0.45 for the faithful as native speakers, STI ≥ 0.50 for friars as non-native speakers of Latin) can be achieved for 50% of the audience in the choir area and for the entire audience in the back area in favourable conditions (fully occupied church, audience addressed from dedicated speaker positions), (2) the position of the pulpit (close to the audience and considerably elevated above it) is more favourable than the position of the altar (remote, barely elevated above the audience), and (3) in unoccupied conditions, fair speech intelligibility can still be achieved in at least 50% of the back audience area with the faithful gathered close to the pulpit, while it is not possible for the front audience area addressed from the altar. The summary conclusion is that the church of St. Francis in its presumed historical layout(s) would fulfil its primary function in a limited capacity. Fair speech intelligibility would likely have been sufficient for the audience to follow liturgical ceremonies conducted in the church, but not without difficulty.