Sound absorption measurements under strongly non-diffuse conditions: the case of the Pastrana tapestries at Meadows Museum in Dallas

Tapestries have long been considered as alternate means to decorate walls, often combining refined craftsmanship with the use of expensive materials like silk and gold. However, besides their decorative function, tapestries often contributed improvements to indoor conditions, and particularly room acoustics thanks to their sound absorption. The acoustic properties of such materials, although predictable with relative accuracy depending on their physical characteristics, are rarely measured in the literature. Taking advantage of the temporary installation of the Pastrana tapestries at Meadows Museum (Dallas), the reverberation time with and without the tapestries was measured. Despite the non-diffuse conditions observed in the room, the results of the measurements were used to explore the possibility to derive absorption coefficients by means of an indirect approach based on the use of a geometrical acoustic model. Results obtained with this method proved more reliable than those obtained using classical formulas, and they were in agreement with theoretical values derived for thin porous materials of similar characteristics.