<p>Steady-state field near the structure.</p>

<p>Magnitude of the steady-state velocity potential at <i>f</i> = 500 Hz over a narrower 6<i>L</i> window centred on the structure; <i>a</i> = 0.05 m, <i>L</i> = 0.10 m, <i>T</i> = 350.0 N/m, <i>N</i> = 24, <i>M</i> = 32 with Lanczos filtering. Physical interpretation: the amplitude jumps at that are barely visible in <a href="plosone.org/article/info:doi/10.1371/journal.pone.0358579#pone.0358579.g011" target="_blank">Fig 11</a> are now resolved as a step in the magnitude controlled by the porous impedance factor of <a href="plosone.org/article/info:doi/10.1371/journal.pone.0358579#pone.0358579.e035" target="_blank">Eq (6)</a>.</p>