Data from a large eddy simulation of oblique shock wave/turbulent boundary-layer interaction in a duct flow with side walls is used to study the relation between the main separation zone and a small corner separation. The weighted power spectral density of wall pressure shows the expected low frequency peak below the reflected shock wave on the test surface. Low frequency peaks are also observed close to the corner, on both the test surface and on the side wall. The peaks occur at the same distance from the corner, at two different streamwise locations corresponding approximately to the start and end of the mean corner reverse flow region. Two point correlations of a low-pass filtered pressure signals are assessed. Both the main separation zone and the corner separation are shown to have significant negative correlations of wall pressure, i.e. to be out of phase, when comparing the start of reverse flow with locations just upstream of reattachment. This is consistent with previous experimental investigations of spectral coherence. None of the two-point correlation results show any connection between the low-frequency motions in the corner and those near the centre of the duct, so a conclusion from the present study is that, at least for the particular shock strength studied, the low-frequency responses in the corner and on the main test plate are independent phenomena.