Application of acoustic fabrics to improve the insertion loss of a partial enclosure

The sound absorption coefficient, transmission loss, and transfer impedance of different sound absorbing fabrics are measured. It is shown that the properties are similar to microperforated panels. Using microperforated panel equations, effective hole diameter and porosity are determined via a least squares curve fit. The effective parameters can then be used to predict the sound absorptive performance for different cavity depths. It is demonstrated that the fabrics have good sound absorptive performance over a wide range of frequencies. The fabric was then positioned in a partial enclosure. Single and double layers of the fabric were placed over an opening and the insertion loss as a result of fabric application was measured. The insertion loss is increased by approximately 5 dB if two layers of the fabric is used.