Sound absorption characterisation of woven materials. Case study: auditorium restoration

Nowadays building conservation and refurbishment draw the attention of the world we live in. In particular, in the public sector, the change of occupancy is commonly used in order to maintain the existing functional layout of spaces and the original structure of the building. Further improvements need to be also considered in order to save the indoor environmental quality. A case study is provided below by the analysis of acoustical performances of an auditorium in Italy, the historical S. Giorgio Palace in Genoa. The palace was built in 1260 and it was the most important public palace in the town; afterwards it became the headquarters of the Port Authority in 1903. Although the high reflective materials covering the interior surfaces provide high values of reverberation time, the hall is mainly used as a conference hall. The acoustical project of restoration, approved by the Ministry of Italian Cultural Heritage, allows only the application of woven materials for floor and curtains, which can be easily removed in case of a change of destination to respect the historical and architectural value of the hall. Acoustical measurements, by means of the impedance tube, have been performed up to now in order to define the best woven materials to improve the overall acoustic performances of the hall. The normal incidence sound absorption coefficient of different samples of carpet have been tested. A procedure for the samples location in impedance tube measurements has been outlined. Carpet is a textile material with a good sound absorption, mainly at high frequencies. In order to improve its acoustic properties at low frequencies a multilayer system composed of carpet and felt having different characteristics have been experimentally investigated and the optimal configuration has been defined. .