Rediscovering the Acoustics of a XII-Century Rotunda through FDTD Simulation

Rotundas are circular domed architectures widespread in Western and Eastern territories of the Roman Empire since the time of the early Christianity. While Latin-cross churches were employed to host public masses, centrally planned buildings were often utilized for Baptismal rituals or by monks for private praying and chanting. This latter particular use of rotundas is closely related to the acoustic peculiarities of the architectures, that provide intimacy and, at the same time, enough reverberance for vocal support. The present paper is focused on a XII-Century rotunda located in Bologna (Italy), still preserved. The worship space was incorporated within a XIX-Century villa and it was recently rediscovered after restoration. The 3-D virtual model was obtained through laser scanning techniques and then properly simplified to be adapted to acoustic requirements. A finite-difference time-domain (FDTD) model using frequency-dependent impedance boundary conditions was calibrated based on acoustic measurements. The possibility of wave-based algorithms to naturally compute edge diffraction and wave interference allows employing of the FDTD code as a research tool for the analysis of the diffraction from the niches in the sidewalls, or other acoustic effects due to this curved and domed space of the past.