# Simplified Fly Tower Modeling for Preliminary Acoustic Predictions in Opera Houses
## 1 Introduction  
The acoustic field of an opera house is difficult to predict. An important reason is represented by the absorption characteristics of the stage area, which vary from time to time, according to the opera piece layout, even if, recently, new more stable conditions seem to be established. Other important reasons are related to the fly tower volume, which varies from theater to theater and is used as a storage space in its upper part and as a set area in its lower one; consequently, the definition of its volume for acoustic prediction modeling becomes critical. Starting with the analysis of possible stage conditions and considering the stage theater plan regulations and rules, the paper aims to find a simplified fly tower model as a fixed reference for preliminary acoustic predictions in opera houses, avoiding the above-cited uncertainties, ensuring acoustic quality independent of the set form on stage, and minimizing the effects of variable set elements. In the Renaissance, the main forms of stage set were two: one that took up the Greek tradition of the walled-up stage back, and the other in which the Depth of the scene was free, and therefore suitable for any game of invention, which also took over in Baroque theaters. The birth of Baroque Theater [1] can be traced back to the 16 th century with the birth of melodrama, the so-called'recitativo'. In that period, the treatise writers began to definethe exact references on the subject, so, at that moment, the scientific beginning of modern scenography and stagecraft was identified. In this paper, the stage evolution over time, from a traditional set to a new digital Baroque scenography, has been used to identify possible acoustic absorption distributions on stage. With the increase in scenography and mechanical needs in a period that includes the seventeenth and eighteenth centuries, the show enriched the dynamics of the performances, and the personality of the stage technician acquired value and authority. This prerogative was typically Italian, and the protagonists ([PERSON], [PERSON], [PERSON], and the [PERSON] family) went around the world to amaze the most varied and distant audiences (Figure 1a,b). As the scene changes multiplied, the relief scenography was supplanted by a scenography painted on mounted canvases, to present maximum maneuverability. The painted scenery, in fact, was composed of more agile elements: the wings replaced the wooden panels, and the backdrop became the principal one. The new shape of the Baroque Theater was based on the horseshoe plan and dominated theater design for 200 years until the 20 th century [2]. By the late eighteenth century, the scenic technique was formed, and, only in the twentieth century did a new experimentation for the scenography begin. In that period, in fact, it started to be conceived no longer only in a decorative and illustrative dimension, but by constructing the space of action as artwork, with autonomous expressiveness through shapes, volumes, lights, and colors, excluding also real animals on stage [3,4]. The space of the scenic representation became a three-dimensional painting that the scenographer created with the compositional freedom of a painter, while still being able to arrange in his own language volumes and plastic masses to be juxtaposed on the stage. Because of the large number of opera pieces and different scenarios, this paper considers their average equivalent sound absorption area, subdivided into three groups with increasing absorption characteristics, without classifying the scenery materials according to their different historical periods. While the research identifies a new set trend, the modern one, different from the previous one (the traditional one), when chromatic qualities of the surfaces and beams of real, vibrant, directional light became a dramatic and theatrical element of the representation.