Determination of effective parameters of acoustic fabrics including sensitivity study

The sound absorption coefficient and transmission loss of different sound absorbing fabrics are measured and it is shown that the fabric may be modeled using the equation commonly used for microperforated panels. Normal incident sound absorption can be measured with a given depth, and then an effective perforation diameter and perforation rate can be determined via a least squares curve fit. Inclusion of the fabric mass in the calculations is optional in the four cases considered. A sensitivity study is performed, and it can be concluded that determination of effective parameters via curve fit has advantages especially when perforation diameter or perforation rate is small. The results of the sensitivity study are also relevant to many commercially available microperforated sound absorbers. It is demonstrated that the effective parameters can be used to predict the real and imaginary parts of transfer impedance for use in simulation models. In addition, effective parameters can be used to predict the sound absorptive performance for different cavity depths and at higher and lower frequencies. Moreover, the transmission loss through a single layer or multiple layers of fabric can be determined.