The generalized impedances allow to characterize a one-way thermal system whose two
faces are accessible. From experimental measurements of the flux densities and variations in
temperature in the access faces of a homogeneous material, the two generalized impedances of
storage and transfer are calculated in the frequential field. The theory of the thermal quadripole
enables to determine a theoretical expression of these impedances. After a sensitivity study which
underlines the accessible parameters and the optimal frequency band, an optimization procedure of
the setting of the ideal model of one of the two impedances on the corresponding experimental
curve allows to identify the effusivity and the thermal diffusivity of material. The method is applied
to the study of a sand with three water contents.