TY - JOUR AU - Salissou, Yacoubou AU - Panneton, Raymond PY - 2007/09/01 Y2 - 2024/03/28 TI - An index of heterogeneity of sound absorbing porous materials JF - Canadian Acoustics JA - Canadian Acoustics VL - 35 IS - 3 SE - Proceedings of the Acoustics Week in Canada DO - UR - https://jcaa.caa-aca.ca/index.php/jcaa/article/view/1966 SP - 196-197 AB - An Index of heterogeneity, through-thickness homogeneity (TTH), of sound absorbing porous materials is calculated. The calculation of this TTH index only requires impedance tube measurements of the acoustical surface impedance on both faces of the tested material. A two-layer rigid frame porous system representing a single porous layer with a sudden change in its physical properties is studied to verify the validity of this TTH index. The sound absorption coefficient, complex wave number, and characteristic impedance of this equivalent single layer are computed in the normal and inverted positions. The heterogeneity of a material can be quantified by the average relative standard deviation (ARSD) of a bulk property measured respectively in both normal and inverted configurations. The ARSD of the three latter bulk properties are computed to identify the most sensitive bulk property to TTH. ER -