“…To provide a simple yet nontrivial example, consider in the case where and for parameter , with domain , , , and boundary conditions specified by . This example is based on the case of acoustic waves in conical geometries where corresponds to the cross‐sectional area and k the opening angle of the cone, . It follows that , and the linear eigenvalue relation is We note that in the limit we see that and , whereas for this commensurate structure is lost, as illustrated by Fig.…”