Buratti C., Cotana F., Vergoni M.

San Lorenzo Cathedral in Perugia is the most important religious building of the town; its construction started in 1300 and finished only in fifteenth century. The church is a typical hallenkirche, in fact the main nave and the two side aisles have the same height: this particular architectural structure causes a bad acoustic quality of the church. The aim of the present paper is to determine the current acoustic situation and to compare seven different electro-acoustic systems proposed by different firms. A measurement session was organized and the main acoustic parameters were measured: reverberation time (T60), clarity and definition indexes (C80 and D50), STI and RaSTI. Furthermore, a speech intelligibility test, in compliance with ISO TR 4870, was carried out in the cathedral to obtain a subjective judgement about sound intelligibility. Each firm installed a demo version of the proposed solution, trying to reproduce the real situation after the installation, and for each one a measurement campaign was carried out. Finally, a technical-economic analysis was carried out and the best solution was chosen respecting the great historical value of the church. A post-operam measurement session was conducted to check the effective benefits on the measured acoustic parameters.