Luca Barbaresi

Analysis of acoustic behavior of bare CLT floors for the evaluation of impact sound insulation improvement

Estimation of the impact sound insulation of horizontal partitions, evaluated from the performance of basic components according to EN 12354-2, does not provide satisfactory results when applied to floors made of Cross-Laminated Timber (CLT) elements. One of the most interesting reasons for this limited match between predicted and measured impact noise values is the difficulty of correlating the reduction of the impact sound pressure level of the floor covering, measured in a laboratory on a concrete slab, with the actual behavior on a bare CLT floor. Reported here are the results of laboratory evaluations, independently carried out by various researchers on similar CLT structures. The purpose of this study is to identify the empirical spectrum of the normalized impact sound pressure level of a reference floor made according to CLT technology, to provide a simple and useful tool for estimating the noise insulation performances of this type of building element.

Experimental measurements of flanking transmission in CLT structures

This paper discusses the results of an experimental campaign that led to the characterization of flanking transmission in CLT structures with different connection systems. The vibration reduction indices Kij were measured in accordance with the ISO 10848-1 standard in order to provide data suitable to calculate the apparent reduction index according to the EN 12354-1 standard. The research explored several vertical and horizontal junctions on which different number and the type of screws and plates, different CLT panels, and resilient materials at the wall-floor junction were tested. The results show that the Kij along different transmission paths have a specific trends in frequency that depend on the fastening system and the mutual connection of the panels. Moreover, the analysis shows great discrepancies among measurements performed on CLT panels provided by different manufacturers. The results call for a deeper investigation concerning the mechanical/acoustical characterization of the panels.

Improvement of acoustic and thermal performances of façades on retrofit buildings

Deep renovation of existing buildings represents an important strategy to go beyond the standard energy retrofit (as the increasing of thermal insulation of building envelope) and to provide more benefits to residents considering non-energetic aspects, like the improvement of architectural quality of building and of indoor life quality. In this context, facades additional elements (balconies, solar greenhouses, etc.) can be effective solutions in order to increase thermal and acoustic performances as well as providing a more living space to the outside. This paper analyzes and compares different technical construction systems for facade improvement in order to define robust solutions correlated both to outdoor climate context (to increase energy performances towards nearly Zero Energy Buildings) and to outdoor noise for a better acoustic sound insulation. A case study is presented, and dynamic energy simulations, performed on a building made with materials and construction technology widespread in Italy ...

A loudspeaker orchestra for opera houses studies

A “Loudspeaker Orchestra” is an array of loudspeakers with a well-defined setup and layout. Initially proposed by contemporary composers for innovative performances (e.g., the “Acousmonium” used by the Groupe de Recherches Musicales in the 1970s), in the last years, the Loudspeaker Orchestra has been used for MIMO acoustic measurements in concert halls. In the present work, a Loudspeaker Orchestra for measurements in opera houses is proposed, taking into account the acoustic differences between a concert hall and an opera house. In fact, in a concert hall, the orchestra plays on the stage, while in an opera house, the orchestra plays in the pit, with a different layout, a smaller instrumental ensemble, etc. In a concert hall, the soloists are placed near the conductor, while in an opera house they move all over the stage, due to dramatic reasons. Basing on previous studies on room criteria and experiences with real orchestras, the authors proposed a Loudspeaker Orchestra layout for opera houses. In this w...

Numerical study of wind-driven natural ventilation in a greenhouse with screens

Abstract This paper is devoted to the CFD study of wind-driven ventilation in a greenhouse, with particular focus to the effect of screens on the inner airflow distribution. Although the use of shading screens to cover agricultural crops has been constantly increased to reduce high radiation loads, their effect on airflow distribution within the greenhouse is still not fully understood. In this paper, CFD simulations of the ventilation in a greenhouse with and without screens are performed, by means of a finite volume CFD code (Ansys-Fluent 17.2), with a standard k- e turbulence model, together with proper user defined functions (UDF) for the inlet velocity and turbulent profiles. The screens have been modeled as porous surfaces and the porosity and the permeability have been obtained experimentally and set into the model. The code has been validated by a comparison with velocity measurements performed in a greenhouse owned by the University of Bologna. Comparisons between the airflow velocity patterns obtained within the greenhouse with screens and without screens have been obtained for different external airflow velocities. The cases with screens show a more uniform distribution of velocity field inside the greenhouse than the cases without screens, especially near the crops. All the cases show that screens strongly affect the airflow velocity distribution inside the greenhouse and the distribution of volume flow rates through the vents. This work shows how the characteristics of the screens and their positioning near the vents are critical for the ventilation within a greenhouse.

Overall indoor quality of a non-renewed secondary-school building

This work is the result of a field study about overall comfort aspects performed in a secondary-school building in the surroundings of Bologna during the winter season. The campaign aimed at describing overall comfort aspects of the school both from an objective and a subjective point of view, thus a questionnaire was administered to pupils during ongoing lessons to compare physical measurements and subjective responses. The monitored attributes and items concerned typical indoor quality aspects: acoustical, thermal, indoor air, and visual quality. As weak points emerged from the data analysis, possible solutions are illustrated, focusing on acoustics and optimizing effectiveness and cost.

Realization of a measurement system for physical and acoustic measurements on brick walls

Aim of this study is the development of a system for the measurement of frequency values of some physical variables such as the damping factor, the thickness of a structural element, the structural reverberation time and the longitudinal wave speed propagation in light brick walls. Such variables are required by the UNI EN 12354-1 normative for the analytical estimation of the sound reduction index R of monolithic elements in the laboratory. The results of the calculation, as a function of frequency, will be shown and compared with the measured values of the sound reduction index R.