Featured Application: The work aims to give more insights into the relation between the sensitivity of the simulated objective parameters and the software input parameters for open-air ancient theatres. It is meant to raise awareness on the use of predictive acoustic software for unconventional outdoor environments in order to validate the possibility of re-using them as performance spaces.
Abstract:Nowadays, ancient open-air theatres are often re-adapted as performance spaces for the additional historical value they can offer to the spectators' experience. Therefore, there has been an increasing interest in the modelling and simulation of the acoustics of such spaces. These open-air performance facilities pose several methodological challenges to researchers and practitioners when it comes to precisely measure and predict acoustical parameters. Therefore this work investigates the accuracy of predicted acoustical parameters, that is, the Reverberation Time (T 20 ), Clarity (C 80 ) and Sound Strength (G), taking the ancient Syracusae open-air theatre in Italy as a case study. These parameters were derived from both measured and simulated Impulse Responses (IR). The accuracy of the acoustic parameters predicted with two different types of acoustic software, due to the input variability of the absorption and scattering coefficients, was assessed. All simulated and measured parameters were in good agreement, within the range of one "just noticeable difference" (JND), for the tested coefficient combinations.
The present study evaluates the effect of soundscape and lightscape variations on the perceived safety and perceived social presence in a pedestrian area through laboratory experiments. Thirty-one participants were presented with nine different virtual scenarios, in which the same underpass was reproduced under different soundscape and lightscape conditions. The participants were asked to assess each scenario considering 10 items related to perceived safety and perceived social presence. A principal component analysis allowed the 10 items to be reduced to two principal components, namely “perceived safety” and “perceived social presence”. A two-way repeated measures ANOVA analysis was conducted to assess the effect of modifications of both the soundscape and lightscape on the two components. The obtained results showed that the soundscape had an effect on both the perceived safety (p < 0.05) and perceived social presence (p < 0.05), while the lightscape variations implemented in this experiment only had a statistically significant effect on the latter (p < 0.05). The results of such studies may be of interest for public design and management as they may be conducted by means of non-intrusive and cost-effective techniques.
The emerging field of archaeoacoustics is attracting increasing research attention from scholars of different disciplines: the investigation of the acoustic features of ancient open-air theatres is possibly one of its main themes. In this paper, the outcomes of a measurement campaign of acoustical parameters in accordance with ISO 3382-1 in the ancient theatre of Tyndaris (Sicily) are presented and compared with datasets from other sites. Two sound sources were used (firecrackers and dodecahedron) and their differences were analysed. A very good reproducibility has been shown between the two measurement chains, with differences on average of 0.01 s for reverberation time T20, and less than 0.3 dB for Clarity C50 and C80 and for sound strength. In general, results show that the reverberation time and strength of sound values are relatively low when compared with other theatres because of the lack of the original architectural element of the scaenae frons. When combining this effect with the obvious condition of an unroofed space, issues emerge in terms of applicability of the protocols recommended in the ISO standard. This raises the question of whether different room acoustics parameters should be used to characterise open-air ancient theatres.
Open-air theatres are considered unconventional environments for acoustic simulations: they usually do not preserve the scenae and are only characterised by the cavea and the orchestra, which lead to very few important reflections. There is still debate on the most suitable parameters to be used for the model calibration according to measured data. In this study the model of the ancient theatre of Syracusae has been simulated with a geometrical acoustic-based software, Odeon (v13.2). In particular this work aims to investigate whether G (Strength) and DRR (Direct-to-Reverberant Ratio) could be considered as suitable parameters to be used for the calibration of measured data and to test the design of new scenarios.
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