Figure 2
Elaborate waveguide with orthogonality-breaking structures.
(a) Schematic illustration of the experimental set-up. A diameter-modulated stainless steel pipe is shown in the upper inset. The symmetric sound waves were regulated to low-order transverse modes, propagated through the structured waveguide and were detected by a microphone housed in a long tube. (b) Multi-mode interactions between the fundamental (green dash-dotted lines), first (black dashed lines) and second (solid red line) modes as well as the dispersion curves of the structured waveguide (blue dots). (c) Sound transmission exhibiting extraordinary transparency in the forbidden band. The solid red line represents the measured axial transmission and the blue dashed line represents the calculated power transmission.
