Spatial distribution of monaural acoustical descriptors in historical Italian theatres

In order to qualify a performance space, ISO 3382 recommends a minimum number of receiver positions as a function of hall size, to be selected according to given rules. Different acoustic criteria and different degrees of accuracy may require a different set of measurement points. The Charta of Ferrara extends these method to historical Italian theatres, characterized by a horseshoe shaped audience, a series of tiers and a gallery. In order to verify the representativity of the number and disposition of the measurements points proposed in the Charta, a measurement campaign has been conducted in three historical medium sized Italian theatres: the Masini Theatre in Faenza, the Rossini Theatre in Lugo and the Bonci Theatre in Cesena. Impulse responses have been measured at each listener position. Monaural descriptors of ISO 3382 have been extracted from the impulse responses and analyzed. The statistical frequency distribution of each parameter has been calculated, according to similar literature for different shaped theatres. Then various reduced sets of receivers, selected from the total ensemble according to the procedure of ISO 3382, Charta of Ferrara, and exploiting symmetries, have been compared. Differences between different receiver sets have been found, and dissimilarity between seats have been related to different acoustical zones of the hall.