An experimental study of Sound Transmission Loss (STL) measurement techniques using an impedance tube

Abstract

A comparison between the two sound transmission loss (STL) measurement techniques using an impedance tube (i.e. two‐load method and anechoic termination method) is presented. A modified B&K type 4206 impedance tube has been designed and built. STL tests have been carried out for three homogeneous and isotropic materials with disk‐type test samples of identical diameters and different thicknesses. In addition, the results have been compared with those of the classical and more reliable method of two‐room. For both methods, the effect of downstream (tube termination) boundary conditions have been completely studied. The two‐load method yields results which matches with two‐room measurements, especially when the two boundary conditions are considerably different. The anechoic termination method, on the other hand, is significantly dependant on the termination boundary conditions.