The ancient theatre favors the aggregation of the spectators around the plays, ensuring thus the optimum sound distribution and, consequently, contributing to the creation of an impressive acoustic sensation. The ancient engineers focused to the phenomena of reflection and reverberation. In those buildings, problems such as the architectural composition and form, the visual and acoustics, static and location, were resolved with simplicity and entirety. Several disciplines such as architecture, archeology and acoustics were interrelated to serve this kind of entertainment. Gradually, the theatre became the space where drama was performed during the ancient times. That means that within the theatrical space another one was evolved, meaning the scenic space. (1) This scenic space has been transformed many times through the passage of time. The Greek theatres as a response to a network of preexistent spatial relationships underwent a process that defined their architectural components. They can be classified in several types, such as the Minoan, the Pre- Aeschylean, the Classic, the Hellenistic and the Roman types (2). During this evolution the development of the scene building was the most evolved but unfortunately in most cases only the ruins of its footings still survived. This study is focused on the evaluation of the effectiveness of the scene building, as the theatrical space which hosts the speech.

The first part of the present research refers to the evolution of the theatre in antiquity, revealing its connection with the social situation of each period and its direct reflections on the architectural building of the theatre. This part serves as the basis of our following analysis. Particular attention has been paid to the evolution process of the scenic building. The next part explores the researches of Fr. Canac, headed the Center of Scientific Industrial and Maritime Research of Marseille, in the ancient theatres. Its geometrical method is used in order to propose scenery which would improve the acoustic conditions and provide guidelines for the scenery design in the ancient theatres. Finally the generic scenery proposal is tested through mathematical calculations, computer simulations (Odeon acoustics 13.1) and listening tests.

The principal aims of the study are:

(a) to investigate the scenery evolution of the theatre and restitute the most suitable form of scenery for the theatrical space. Scenery must respect the purpose of each theatrical space. In particular in the ancient theatres where drama plays were born, the scenery design must focalized on speech requirements.

(b) to examine the acoustic importance of the theatrical elements (cavea orchestra, parodoi and in particular the scenic elements) for the completion of the scenic design enabling the reproduction of a passive acoustic function. In account of this guidelines, useful for the designers, are provided.

At this point is important to underline the boundaries which this research must respect. Ancient theatres are monuments, that have survived through centuries of history. Therefore, our only right is their protection for future generations. The restoring of the ancient theaters (and their probable contemporary use) becomes more complex if one is searching for the original theatrical form of each period and, subsequently the interpretation of the functional requirements for the revival of the ancient drama. Additionally, other difficulties, such as the lack of comprehensive researches on the field, make the task of the contemporary designer even more difficult.

The guidelines provided from by this study intent to comply the harmonic development of the scenery with the rest of the building, in an attempt to respect the nature, function and particularly the current situation of these monuments. So it will be a benefit for the designers as also a positive input which is hoped to motivate and guide their creativity in a more sustainable way.