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Understanding the acoustics of Papal basilicas in Rome by means of a coupled-volumes approach
Full text linkThe paper investigates the acoustics of the four World-famous Papal Basilicas in Rome, namely Saint Peter׳s, St. John Lateran׳s, St. Paul׳s outside the Walls, and Saint Mary׳s Major. They are characterized by different dimensions, materials, and architectural features, as well as by a certain number of similarities. In addition, their complexity determines significant variation in their acoustics depending on the relative position of source and receivers. A detailed set of acoustic measurements was carried out in each church, using both spatial (B-format) and binaural microphones, and determining the standard ISO 3382 descriptors. The results are analyzed in relation to the architectural features, pointing out the differences observed in terms of listening experience. Finally, in order to explain some of the results found in energy-based parameters, the churches were analyzed as a system of acoustically coupled volumes. The latter explained most of the anomalies observed in the distribution of acoustic parameters, while showing at the same time that secondary spaces (aisles, chapels) play a different role depending on the amount of sound absorption located in the main nave
Subjective study of preferred listening conditions in Italian Catholic churches
No full textThe paper describes the results of research aimed at investigating the preferred subjective listening conditions inside churches. The effect of different musical motifs (spanning Gregorian chants to symphonic music) was investigated and regression analysis was performed in order to point out the relationship between subjective ratings and acoustical parameters. In order to present realistic listening conditions to the subjects a small subset of nine churches was selected among a larger set of acoustic data collected in several Italian churches during a widespread on-site survey. The subset represented different architectural styles and shapes, and was characterized by average listening conditions. For each church a single source-receiver combination with fixed relative positions was chosen.. Measured binaural impulse responses were cross-talk cancelled and then convolved with five anechoic motifs. Paired comparisons were finally performed, asking a trained panel of subjects their preference. Factor analysis pointed out a substantially common underlying pattern characterizing subjective responses. The results show that preferred listening conditions vary as a function of the musical motif, depending on early decay time for choral music and on a combination of initial time delay and lateral energy for instrumental music
La ricerca dell'equilibrio fra chiarezza e riverberazione nella progettazione acustica delle chiese
No full textOn the use of microphone arrays to visualize spatial sound field information
No full textMicrophone arrays represent today a state of the art solution to many acoustic problems. In architectural acoustics, for example, one of the most interesting applications is the possibility to analyse the directional information associated to a given reflection. Ambisonics microphones could provide similar information based on zeroth and first order spherical harmonic decomposition, but larger microphone arrays allow the determination of higher order components providing even better accuracy. In this case, directional information may be obtained through beamforming techniques that, although potentially more accurate and capable of resolving simultaneous reflections, are computationally heavier and provide a "discrete" sampling of the sound field. The paper compares the localization accuracy of a 32 channel microphone array by processing its output using a simple Ambisonics decomposition and a spatial sampling carried out using 32 "virtual" third-order hyper cardioid microphones. In addition, a comparison with conventional Ambisonics microphones is provided in order to point out possible differences. Results show that, when single reflections are involved and the sound field is highly polarized, the Ambsionics decomposition given by the microphone array gives good accuracy over the whole spectrum, while conventional Ambisonic microphones shows less stable results and greater variations as a function of frequency. Spatial sampling is intrinsically less accurate but allows a clearer resolution of simultaneous reflection
Identifying acoustical coupling by measurements and prediction-models for St. Peter’s Basilica in Rome
No full textSt. Peter's Basilica is one of the largest buildings in the world, having a huge volume resulting from the addition of different parts. Consequently, sound propagation cannot be interpreted using a conventional approach and requires experimental measures to be compared with statistical-acoustics and geometrical predictions in order to explain the interplay between shape, materials, and sound waves better. In previous research one of the most evident effects, the surprisingly low reverberation time, was believed to result from acoustical coupling phenomena. Taking advantage of more refined measuring techniques available today an acoustic survey was carried out and the results were analyzed using different methods, including Bayesian parameter estimation of multiple slope decays and directional energy plots, which showed that coupling effects actually take place, even though measured reverberation times were longer than those given in previous studies. In addition, experimental results were compared with geometrical- and statistical-acoustic models of the basilica, which showed that careful selection of input data and, in statistical models, the inclusion of phenomena such as direct sound radiation and non-diffuse energy transfer, allow obtaining accurate results. Finally, both models demonstrated that reduced reverberation depends more on increased absorption of decorated surfaces than on coupling effects
Room acoustic modelling of textile materials hung freely in space: from the reverberation chamber to ancient churches
Full text linkThe aim of this study is to investigate how sound absorbing materials like curtains should be modelled in geometrical acoustic (GA) software when hung freely in space. The use of these tools is widespread today. Whatever the scope of the simulation, dealing with textile materials can be particularly challenging as they both absorb and transmit sound, and absorption is dependent on distance of the walls. Therefore, care must be taken to enter properly validated data. Absorption coefficients found in the literature are measured with samples close to wall, and are not suitable when materials are hung freely. The effects of material placement on both absorption and transmission coefficients were therefore investigated using scaled-down physical models of a reverberant chamber and a church. Subsequently, GA models of both spaces were used to demonstrate that simulated results are reliable assuming that absorption and transmission coefficients are correctly determined
Acoustics as a cultural heritage: The case of Orthodox churches and of the "Russian church" in Bari
Full text linkArchitecture of Orthodox churches changed very little in its history as a consequence of the strict adherence of liturgy and its related aspects, to the original canons. This has important implications on the acoustics that characterizes such places which is therefore very specific. The paper starts by considering the case of the Orthodox church of San Nicola (also known as "Russian church") in Bari where an acoustic survey was carried out. Innovative measurement tools like microphone arrays were used, allowing the identification of direction of arrival of sound reflections and, consequently, the architectural elements that play a major role on the acoustics. Then, the results of a detailed literature research are used to put the specific case study into a broader context including a large number of Orthodox churches. Results point out the existence of a very specific relationship between acoustics and architecture, supporting the idea that the first must be considered as a cultural heritage as important as the latter
A preliminary investigation on the effects of Baroque modifications on the acoustics of former Romanesque churches
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