Acoustic study of the Roman theatre of Pompeii: Comparison between existing condition and future installation of two parametric acoustic shellsa).

Roman theatres have always been the subject of research that takes into account not only acoustics, but also archaeological and architectural aspects. It is difficult to draw the boundary line between these disciplines since the interrelation between the different types of expertise is necessary to allow a good production of contemporary architecture in a specific context, such as a Roman theatre. This paper deals with the acoustic analysis of three specific scenarios in the context of the Roman theatre of Pompeii. The reconstruction of the original form, which represents the first scenario, is based on the recent archaeological findings of the ancient city, which was buried for almost two millennia after the eruption of the volcano Vesuvius. The second scenario envisions a future acoustic shell in the form of a mushroom, where the ceiling is the continuation of the vertical surface. The third scenario consists of a parametric design of a shell, representing a modern style velarium; as the curve creates focusing effects, the addition of reflective panels directs the sound evenly to the audience. These latest two architectural designs are intended to make the archaeological site of Pompeii suitable for live concerts and contemporary venues. The digital model representing the current conditions was calibrated with the measured values; the calibrated model was used to study the design of two parametric shell options, proposed as alternatives to provide good acoustics to the audience. The simulated results indicate that the main acoustic parameters are closer to or within the optimal values, resulting in a significant improvement in the acoustic performance of the space.

From discoveries of 1990s measurements to acoustic simulations of three sceneries carried out inside the San Carlo Theatre of Naplesa).

Many acoustic studies have been conducted in the San Carlo Theatre of Naples over the centuries. The discovery of valuable acoustic measurements from 1998 led the authors to photograph the architectural and acoustic conditions of the Theatre prior to restoration works in 2008. As the first opera house built in Europe, the San Carlo Theatre has always offered a rich artistic programme, making this historic building synonymous with classical music in Naples. From the great variety of operas, three specific sceneries have been selected to analyse the acoustic response based on different geometries and materials located on stage. Acoustic simulations have been performed based on site measurements, starting from a digital model that reproduces the geometry and absorbing coefficients of the materials existing in the Theatre. Using the recorded impulse response, the monoaural and binaural acoustic parameters have been obtained from the acoustic simulations and thereafter compared among the Elektra, Traviata, and La clemenza di Tito sceneries. The results in terms of reverberation highlight that La clemenza di Tito absorbs the high frequencies better than the other two sceneries. Under a clarity perspective, all the sceneries have values above the optimal range limit set for opera houses, although it is typical of other opera theatres built in the same period. A detailed historical background on the architectural changes of the San Carlo Theatre over the centuries is also given to understand the digital reconstruction that modelled the acoustic behaviour of this prominent cultural heritage building.

Modeling acoustic metamaterials based on reused buttons using data fitting with neural network.

Metamaterials are designed by arranging artificial structural elements according to periodic geometries to obtain advantageous and unusual properties when they are hit by waves. Initially designed to interact with electromagnetic waves, their use naturally extended to sound waves, proving to be particularly useful for the construction of containment and soundproofing systems in buildings. In this work, a new metamaterial has been developed with the use of a polyvinyl chloride membrane on which buttons have been glued. Two types of buttons were used, with different weights, placing them on the membrane according to a radial geometry. Each sample of metamaterial was subjected to sound absorption coefficient measurements using the impedance tube. Measurements were made using the samples by setting three configurations, creating a cavity with different thicknesses. The results of the measurements were subsequently used as input for training a simulation model based on artificial neural networks. The model showed an excellent generalization capacity, returning estimates of the acoustic absorption coefficient of the metamaterial very similar to the measured value. Subsequently, the model was used to perform a sensitivity analysis to evaluate the contribution of the various input variables on the returned output.

Water Resistant Self-Extinguishing Low Frequency Soundproofing Polyvinylpyrrolidone Based Electrospun Blankets.

This paper shows that an eco-friendly electrospinning process allows us to produce water resistant sound absorbers with reduced thickness and excellent sound-absorption properties in the low and medium frequency range (250-1600 Hz) for which which human sensitivity is high and traditional materials struggle to match, that also pass the fire tests which are mandatory in many engineering areas. The structure and composition were studied through Scanning Electron Microscopy (SEM), Fourier Transform InfraRed (FTIR) Spectroscopy and ThermoGravimetric Analysis (TGA). The density, porosity and flow resistivity were measured. Preliminary investigation of the thermal conductivity through Differential Scanning Calorimetry (DSC) shows that they have perspectives also for thermal insulation. The experimental results indicate that the achievements are to be ascribed to the chemical nature of Polyvinylpyrrolidone (PVP). PVP is, in fact, a polymeric lactam with a side polar group that may be easily released by a thermooxidative process. The side polar groups allow for using ethanol for electrospinning than relying on a good dispersion of silica gel particles. The silica particles dimensionally stabilize the mats upon thermal treatments and confer water resistance while strongly contributing to the self-extinguishing property of the materials.