Method for controlling boundary condition effects on the measurement of acoustic properties of small samples in tubes

As standard ASTM E2611 reveals, the normal incidence sound transmission loss measured on a small sample in an acoustic tube is not only property of material but also strongly dependent boundary conditions (generally unknown) and way mounted. This article proposes experimental method to control effects lateral tube. The main objective deduce properties “client element” (material sample) from global patchwork composed by material” known “host support.” Three configurations have be distinguished: patchworks with without impervious rigid interface between elements that cannot identified as equivalent fluids. For each these configurations, use specific based Mixing Rule Method (MRM) or Parallel Transfer Matrix Methods (P-TMM dP-TMM) used reverse proposed. Numerical validations are proposed tubes convenient configuration: surrounded air ring. configuration allows reducing elastic-frame behavior leave limp-frame behavior. methods allow removing effect ring host surrounding material. homogeneous materials, two MRM dP-TMM give similar good results. non-homogeneous materials for modeled fluids, gives