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

Abstract

The present note describes work related to anisotropy of acoustical properties of felt materials being compressed with a rate $\text{n}$ varying from 1 to 4. Following a recent note [1], it is shown that such compression induces some anisotropy, which is small but still significant, clearly visible on the elliptical shape of the tortuosity spatial distribution, and also on the Brewster angle shifts, which are predictible. Some fine experimental studies of the reflection coefficient versus the angle of incidence have been performed and discussed.