Italian Opera Houses Research Articles

ACOUSTIC MEASUREMENTS IN OPERA HOUSES: COMPARISON BETWEEN DIFFERENT TECHNIQUES AND EQUIPMENT

In room acoustics, many objective parameters to quantify subjective impressions have been introduced. These quantities can be measured by using a wide variety of powerful tools and equipment. The results can be influenced by the measurement techniques and instruments used. Furthermore, the results also depend on the measurement positions and on the condition of the hall (full, empty, etc.). The aim of this work is to define a tightly standardized measurement procedure for the collection of a complete objective description of an opera house's acoustics. In this paper some of the results obtained by the authors after measurements made in three different halls are presented. Comparisons were made both between different hardware and software tools (real-time analyzer, DAT, PC-board, source, microphones, post-processing software) and between different measurement methods (interrupted stationary noise, true-impulse, pseudo-random white noise with impulse–response doconvolution, sine sweep) as well as between different positions in the halls, with and without the presence of musicians and audience. The results have shown that the differences obtained when using different measurement techniques and equipment are not of significant importance. The only effective differences were found regarding the recording techniques, as the monaural measurements give appreciably different results from the average of left and right channel of binaural measurements. Slightly different results were alsofound between true impulsive sources (pistol shots, balloons) and omni-directional (dodecahedral) loudspeakers. Attention must be paid to the signal-to-noise ratio, as this can influence the correct calculation of some acoustical parameters. Some differences, not as great as expected, were found in the results with and without the musicians in the orchestra shell and with and without the audience in the hall. This is probably due to the high sound absorption that is typical in Italian opera houses even without an audience. However, important differences were found in the calculation of some acoustical parameters, particularly clarity C 80, by changing positions in the hall.

Acoustics of opera houses: A cultural heritage

An important part of contemporary Italian musical culture has developed inside historical opera houses. An outstanding opera repertory was especially conceived to match these places, both from the architectural and the acoustical points of view. But, while extensive attention is devoted to architectural and historical aspects, the acoustical characteristics of an opera house, that is, the set of listening attributes which make such a place unique among all spaces for music, are still nowadays hardly recognized as being paramount. In fact they can be rightly considered a relevant cultural heritage in Italy and can thus be called acoustical heritage. This new kind of heritage calls for accurate study and attention, both from the scientific and social points of view. To preserve the heritage for future generations, it is necessary to know it precisely and to elaborate means of accurate description. A project with the participation of international specialists has been established to agree on a standardized procedure for acoustic measurements specific to Italian historical opera houses in order to investigate the pecularity of these places. The aim of the project is to give a state-of-the-art acoustic documentation fo some theaters with the possibility of later applying up-to-date acoustical analysis.