Experimental characterization of the freezing of the transmitted pattern in a periodic waveguide

Experimental measurements of the transmitted pressure field through a finite periodic acoustic waveguide reveal a frozen pattern: The spatial distribution of the transmitted field remains invariant with respect to the incident wave. In disordered media, such freezing typically occurs with Anderson localization, resulting in low energy transmission. In contrast, the present experiment confirms recent numerical studies and shows that periodic waveguides can exhibit this phenomenon under two distinct conditions: at frequencies within a bandgap, where freezing is associated with evanescent decay and thus with a low energy transmission; and at frequencies where one Bloch mode propagates, resulting in freezing with higher energy transmission.