Parametric study of the influence of compression on the acoustical anisotropy of automotive felts

The present note describes work related to anisotropy of acoustical propert ies of felt materials being compressed with a rate n varying from 1 to 4. F ollowing a recent note [1], it is shown that such compression induces some anisotropy, which is small but still significant, clearly visible on the el liptical shape of the tortuosity spatial distribution, and also on the Brew ster angle shifts, which are predictible. Some fine experimental studies of the reflection coefficient versus the angle of incidence have been perform ed and discussed. (C) 2001 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.