On-site acoustical characterization of Baroque tapestries: The Barberini collection at St. John the Divine Cathedral

Tapestries represent an important and valuable cultural heritage. In the past they played a significant role in enriching indoor environments, as well as contributing to change the indoor characteristics of the space. Considering typical mounting conditions, acoustics was likely to be strongly affected by hung tapestries. Even though their acoustic properties could be ideally inferred from their physical features, a proper characterization would be preferable to understand how they could modify sound propagation. However, given their dimensions and their delicacy, on-site measurements are often the only option. In the present paper, absorption coefficients of the Barberini tapestries were measured during a temporary exhibition held in the Cathedral of St. John the Divine in New York City. Measurements were carried out in a large chapel with and without the tapestries installed. The effect of acoustical coupling with the adjacent cathedral volume was investigated using Bayesian methods to exclude unwanted influence on the measurements. Results were obtained using either the classical reverberation time formula or the indirect approach based on the use of geometrical acoustic modeling. Finally, results proved to be in good agreement with predictions based on theoretical formulas, once the relevant non-acoustical parameters were estimated.