“…In addition to static black holes [4][5][6][7][8][9][10], it is also possible to create e.g. (static) white hole event horizons [4,6,8,[11][12][13][14][15], rotating geometries analogous to Kerr black holes [16,17], expanding universes [18][19][20] or even (static) two-horizon interactions [21,22]. For those systems featuring a static horizon, the classical frequency shifting of waves at the horizon has been the traditional benchmark to demonstrate analogue gravity physics, although scattering of waves that could not be associated with a horizon has also been observed [6,11,13,23,24].…”