Results for the scattering to the circle of receivers in Figure 7b for the box with an impedance patch in Figure 7b, for six example frequencies. Settings for the ESIE+SS method were as in Table 2. The numerically most challenging receiver positions are marked with solid-line arrows, and the more benign challenging positions are marked with dotted-line arrows. (a) f = 50 Hz. (b) f = 125 Hz. (c) f = 250 Hz. (d) f = 500 Hz. (e) f = 1000 Hz. (f) f = 2000 Hz.