Benoit Beckers & Nicoletta Borgia
Urban Systems Engineering Department
Compiègne University of Technology (France)
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Summary
The evolution of Graeco-Roman theatre, during its thousand years in existence, is interpreted as a two-sided problem concerning geometric acoustics and visual geometry, and, beyond that, as the first step in a more general acoustic model, which encompasses all theatre designs whose primary criteria is capacity.
I. INTRODUCTION
Over the past few years, there has been a renewed interest in the acoustics of ancient theatres. In general, articles on the subject are based on measurements of the sound field carried out in major theatres, such as the ones in Epidaurus and Dodona [1], Aphrodisias and Aspendos.
Sometimes, it is simply a matter of becoming better acquainted with the auditory qualities of these places, where performances are still regularly put on. The problem is that these measurements are often taken when there is no audience present, even though an audience significantly modifies the acoustics of these stone structures. These measurements are also often a pretext to assess simulation programs based on ray tracing [3, 4], which does, or does not, take into account diffuse reflection. It is therefore difficult to deduce the original properties of these theatres which are now in ruins. Indeed, they are sometimes in a remarkable state of
preservation but the marble surfaces have disappeared and the stones themselves are heavily eroded, which obviously affects the specular and diffuse components of the reflected sound.
In our opinion, too much attention is paid to secondary effects as a result of these works (multiple reflections between the stage and the tiers, or between the opposite sides of the tiers), which fade significantly in the presence of an audience. They do not, in any way, explain the beginnings or the function of these theatres, and they scarcely take the motivations of their architects into account, and, finally, cannot direct us in our own architectural projects.
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