Analysis of the acoustic absorption of fabrics in a diffuse sound field and for normal incidence

The use of textile curtains for room acoustic correction is a very widespread practice, especially in situations where it is difficult to effectively take action to the reflective surfaces of the room by installing non-removable absorbers. The definition of acoustic characteristics of these types of absorbers is not easily foreseeable due to the dependence on their physical parameters and the type of installation. They depend also on the quantity of the drapery, intended as the relationship between the actual surface development of the material and its projection on the installation plan. Other researches on this topic have been carried out by analysing the absorption as a function of the material composition, by means of models with equivalent electrical circuits in the case of single fabric and air layer or double fabric and air layers. In this work, sound absorption coefficient of different types of fabrics in many different configurations have been examined. Measurements were performed both in diffuse sound field and for normal incidence. The results of the correlations performed to predict the sound absorption between the different sound fields and between the different methods of installation are presented. The measurements were carried out in the reverberation room of the LabAcus laboratory, Department of Industrial Engineering at the University of Padova, and with the impedances tube of the laboratory of environmental technical physics FisTec, Iuav University of Venezia