Figure 2
From: Acoustic Waveguide Eigenmode Solver Based on a Staggered-Grid Finite-Difference Method
Validation of resonance operator matrix properties. (a) Example of the operator matrix. (b) Convergence tests of the mode solver: the 20 dB/decade slope for eigenfrequency error (40 dB/decade for mode shape) indicates second-order accuracy. (c) Tests of modal orthogonality in three configurations, supporting the Hermitian nature of the resonance operator in the absence of PMLs and the modified orthogonality relation for the lossy case.
