19th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 ...

19th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 SEPTEMBER 2007

THE MODERN USE FOR ACOUSTICAL PERFORMANCES OF THE ANCIENT ROMAN THEATRE OF BENEVENTUM PACS: 43.55.Fw De Gregorio Leda; Iannace Gino; Maffei Luigi; Masullo Massimiliano Dispama- Built Environment Control Laboratory Ri.A.S., Facoltà di Architettura, Seconda Università degli Studi di Napoli, Italia; [email protected] ABSTRACT Ancient Greek and Roman theatres are disseminated on the territory of many countries. This cultural heritage is extremely important for local and national tourism. Nowadays there is also a strong tendency to use these monuments for acoustical performances restoring the ancient function. To support Italian authorities in elaborating guidelines for the modern use of this patrimony, a national research programme has been developed. An important part of the programme is dedicated to the techniques to classify the acoustic quality of these theatres in the past and in the modern age. In this paper are reported results of acoustic measurements performed in the Ancient Roman Theatre of Benevento. The theatre was inaugurated under the emperor Hadrian in the year 126 A.D and completed by Caracalla between 200 and 210 A.D.. During the middle ages the theatre disappeared under the construction of different buildings and become the centre of agricultural and artisan activity. Only recently the theatre was brought to light with an intensive program of consolidation. The theatre is nowadays not only a ancient monument but also the centre of important social activities with national and international festivals of music, dancing, drama. HISTORY OF THE ROMAN THEATRE IN BENEVENTO (ITALY) The Roman Theatre in Benevento, is located in Campania, and is distant 70 km from Naples. It is considered one of the most important work of Roman period in the south of Italy. It was built during the Trajanic period (98-117 A.D.), it was inaugurated in 126 and it was enlarged by Caracalla between 200 and 210 A.D. In origin it contained over 10.000 spectators. The cavea, built on substructures, is semicircular and has tree orders: Tuscan, Ionic and Corinthian. Actually only the lower order remains, it consists of twenty-five arches on pillars featuring Tuscan semicolumns. The arched lintel is completed by a broad cornice. In the lower order the keystone is decorated with bust. In the upper order it was probably decorated with masks. Accesses were provided by arches communicating with the interior trough corridors alternating with flights of steps. The cavea was divided in two maeniana. Over this there was a gallery. The inner wall of the gallery was decorated with niches. The orchestra was semicircular and could be reached from the parodoi. The scaena featured three semicircular niches, the central one being the largest. The rooms, which were decorated with crustae and plaster, are particularly well developed. Two bases of statues dedicated by the city of Beneventum to Hadrian and to Caracalla have been found during restoration. The structures were built in opus caementicium (using river pebbles and mortar). The façade is faced with limestone and bricks are used elsewhere; the steps and the scaenae fronds were in marble. In origin the diameter of cavea was of 98 m, otherwise the diameter of orchestra was of 30 m. After the Roman period the theatre was used as a quarry for building materials, and later the theatre was occupied by dwellings (Figure 1), which were gradually removed starting from years 1920’s , onwards to restore the theatre’s monumental appearance. The church built over a part of the stage building has survived. Actually of the Roman theatre remain fifteen steps, and it can contain only 1.500 – 2.000 spectators. The theatre in the latest years is used for different type of shows: opera, drama, dance and symphonic, jazz and pop music concert. During the annual national cultural meeting “Benevento città spettacolo” the theatre becomes the centre of the most important performances as comedy, drama and musical shows.

The actual dimension (Figure 2) are: diameter of orchestra equals to 13,50 m; external diameter of cavea equals to 23,50 m; each of the fifteen steps has an height equals to 0,40 m and depth equals to 0,70 m; the cavea slope is equal to 30°.

Figure 1.- On the left, theatre occupied by dwelling (1920). On the right the actual state.

Figure 2.- Actual state of the Roman theatre.

ACOUSTIC MEASUREMENTS The acoustic parameters measured are in according to ISO 3382 [1]. Among them the strength G, measured in function of distance from the sound source, seems to be the most important as the open theatre generates few sound reflection. The measurement positions were chosen along three radial lines in the cavea (Figura 3), the first line was placed in the right side of the theatre (seen from the audience), the second line is the centre line, and the third line was placed symmetrically on the left. For each direction were chosen four measurement points along the cavea, (d1, d2, d3, d4) at different distance from sound source location (Figure 3). For evaluating G, the same three radial directions were considered but to collect more information the points chosen along the cavea were eight for each direction. A dodecahedral omnidirectional sound source was placed on the scaena and in the orchestra area. The height of the sound source from the pavement was 1,60 m, it was fed with a maximum length sequence signal generated by a MLSSA analyzer [3], that yielded a sound pressure impulse response for each measuring microphone location. The microphone height was 1,0 m. During the acoustic measurements the air temperature was 21 °C, and the wind was absent.

2 19th INTERNATIONAL CONGRESS ON ACOUSTICS – ICA2007MADRID

Figure 3. Plans, with the three measurement direction, and the two positions of sound source

Figure 3. Section, with the eight measurement points, for evaluation of strength, G.

Figure 5. Sound source on the scaena.


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Figure 6. Average acoustic parameters measured for sound source on scaene and sound source in the orchestra area. 4 19th INTERNATIONAL CONGRESS ON ACOUSTICS – ICA2007MADRID

Figure 6 reports the values in octave bands central frequencies of the acoustic parameters averaged on two positions of sound source (on the scaena or in the orchestra area) and on the twelve measurement points along the cavea. In Figure 7 and in Figure 8, are reported the values of averaged wide band strength G in function of distance from sound source for the sound source position on the scaena and in the orchestra area respectively. Along the cavea, eight measurement points were chosen for each of the three propagation lines (Figure 3). In each of eight measurement points was measured the sound pressure level (Lp) by an integrator sound level meter. The sound power level of dodecahedral omnidirectional (Lw) was preventively measured by the technique of substitution using a reference sound source in a large room. After with the same set up of power amplifier it was measured in the theatre the sound pressure level (Lp). The acoustic parameter strength, G, was evaluated in according to [4]: G = Lp – Lw +31

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Figure 7. Sound source on the scaena. G function of distance. d = 0 corresponds to sound source location.

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The decay of G when the sound source was positioned in the orchestra area (Figure 8) is more regular than in the case of sound source on the scaena (Figure 7). For both configuration the nearest points to the sound source show a decrease of the G value, because in these points there is only direct sound. The measured values of reverberation time (RT), and early decay (EDT) are quite short, as in the theatre there are not large reflection surfaces. The value of reverberation time (RT) at the frequency of 500 Hz increases; this effect is probably due to the scattering of sound by the steps. In fact each step has depth equal 0,70 m, that corresponds to the wave length at the frequency of 500 Hz. The scaena (Figure 3) has only two lateral columns that give few contributes to the reflection of the sound. In the centre of the scaena there are not walls or large columns (Figure 5), that can give substantial contribute to the reflection of the sound. The parameter C is high, probably for the low value of reverberation time and for the absence of ceiling. The excellent values of RASTI (0,81 when sound source was on the scaena and 0,84 when sound source was in the orchestra area) confirm the presence of direct sound components only. The Lateral Efficiency (LF), measured in according to [5], shows for both sound source locations (scaena and orchestra area) very low values; this confirms the lack ness of first reflections components. CONCLUSIONS Acoustics measurements and data analysis suggest that the theatre, although its actual configuration is completely different from the ancient one, can be used, with good results, for speaking (es. drama or comedy). For opera, symphonic, jazz and pop music performances it is strongly suggested to build sound reflection surfaces (between the two lateral columns) on the scaena. The aim is to reinforce the reflection of direct sound and to increase the sound level in the cavea, obtaining an improvement of acoustic parameters. This work was supported by the Italian Ministry of University, Prin 2005.

References: [1] UNI EN ISO 3382: Acoustics - Measurement of the reverberation time of rooms with reference to other acoustical parameter. [2] A. C. Gade, M. Lisa, C. Lynge, J.H. Rindel: Roman Theatre Acoustics; Comparison of acoustic measurement and simulation results from the Aspendos Theatre, Turkey. Proc. ICA 2004. Kyoto Japan. [3] D. D. Rife: MLSSA Reference Manual version 10.0. 1997 [4] G. Iannace, L. Maffei, C. Ianniello, R. Romano. La misura di G negli auditori. Due tecniche a confronto. Atti del XXVII Convegno dell’Associazione Nazionale di Acustica. Genova. 1999. [5] G. Iannace, L. Maffei, C. Ianniello, R. Romano. Studi preliminari per la misura di frazioni laterali con un solo microfono non direttivo” – Rivista Italiana di Acustica, Volume 27, numero 1-2, Gennaio-Giugno 2003, pp. 1-11.
