Roman Theatres and Revival of Their Acoustics in the ERATO Project

The ERATO project was a three-year research project financed by the European Commission under the Fifth Framework INCO-MED Program (2003-2006). The acronym refers to the project title: Identification, Evaluation and Revival of the Acoustical Heritage of Ancient Theatres and Odea. The ancient Greek and Roman theatres are famous for their excellent acoustics. However, it is not generally well known that different kinds of theatres were built, for different purposes and with different acoustical conditions. The development of the Roman theatre types (theatre, odeon and amphitheatre) particularly in the first Century BC is briefly outlined. One aim of the ERATO project has been to investigate the acoustics of the open air theatre and the odeon, using virtual reconstructions be means of computer models of the spaces, completed in accordance with available archaeological information. Musical instruments and short pieces of music have been reconstructed and recordings have been used for auralisation of some theatre scenarios. Ancient Greek and Roman theatres are often considered acoustically perfect. However, the semicircular shape of the audience area in theatres may cause acoustic problems, and there is also evidence that the ancient architects were aware of this. The Roman architect Vitruvius mentions in his famous books on architecture four different kinds of sound reflections in a theatre, one of them called 'circumsonant' which is probably the acoustical phenomenon that we today would name a focused echo. Computer simulations of some examples of ancient Greek and Roman theatres confirm that echo can occur at some places in the audience area. A possible solution to these echo problems could be the introduction of sound absorption in the vertical, concave surfaces in a way similar to that described by Vitruvius for the sounding vessels, i.e. in niches between the seats arranged in a horizontal range halfway up (in the diazoma). Thus it makes sense if the vessels were supposed to act as sound absorbing resonators, although the number of resonators is far from sufficient for having any real effect. The idea and principle of installing resonators in a theatre comes from Aristoxenus (4th century BC), who was a famous Greek philosopher and scholar in music theory. It is concluded that the sounding vessels had no practical importance in the Roman theatres, and Vitruvius was not up-to-date in his writing on theatre design, but relied heavily on older, Greek references.