Computational design: acoustic shells for ancient theatres

Classical theatres are probably the oldest buildings that still fulfil the purpose they were designed for. On the other hand, the environment around them completely changed. We don?t exactly know what their acoustics was in ancient times, but we do know it?s often inadequate today, and that?s the reason why modern performances mostly rely on electro-acoustic amplification systems. Many international charters illustrate the criteria that should be followed in order to balance preservation and fruition of ancient theatres: the Syracuse Charter (2004) gives indication about the acoustics, asserting that temporary structures can integrate the gaps in order to optimize the acoustic performance. The aim of this work was to improve the acoustics of ancient theatres through the use of lightweight removable shells. All the studies were carried out through optimizations in Grasshopper 3D environment. To this aim, it was necessary the implementation of a suitable simulation model. Since, the acoustics in open air theatres differ both from free field and closed rooms a simple ISM (Image-Source Method) algorithm, partially based on François Canac studies, has been developed. An evolutionary solver, Galapagos, has been deployed for the computational morphogenesis and optimization of the acoustic shells. The theatre of Tindari was analysed,the optimization criterium being the maximation of listening positions receiving a sufficient sound level. Finally, the results have been verified using validated acoustics simulation software, which highlighted that also an oversimplified code could be a fast and efficient help in early design stages, leaving space to further implementations.