Comparison of sound propagation from stage and pit to stalls and boxes in an Italian opera house

The features that separate an opera house from a concert hall are the semi-closed performance area, orchestra pit, and the compartmental audience areas, or boxes. The sound propagated from the orchestra pit reaches listeners through barriers and diffraction effects. As well, the sound arriving to listeners seated in the boxes is further limited because it must cross the box openings. In this study, to assess the sound fields of opera houses, the maximum sound pressure of direct sound coming from an impulse response measured in the Teatro Nuovo di Spoleto is investigated using Gre (relative strength), which is the ratio of the sound pressure measured in a hall to an equivalent sound pressure that would be measured at the same distance from the same source to the receiver in a free sound field. Impulse response analyses show that Gre is predicted mainly by the elevation angle from the source to the edges (pit rail and box rails), and that the values of Gre also have high correlations with the interaural cross-correlation coefficient (IACC). Gre is suggested as a useful parameter for quantifying the barrier effect of a pit and for evaluating the architectural design of opera house boxes.