  Analog models of black holes have unequivocally proven to be extremely
beneficial in providing critical information regarding black hole spectroscopy,
superradiance, quantum phenomena and most importantly Hawking radiation and
black hole evaporation; topics that have either recently begun to bloom through
gravitational wave observations or have not yet been investigated in
astrophysical setups. Black hole analog experiments have made astonishing steps
toward the aforementioned directions and are paramount in understanding the
quantum nature of the gravitational field. Recently, a tabletop analog
Schwarzschild black hole has been proposed by placing Bose-Einstein condensates
of photons inside a mirror's cavity, leading to a sink with a radial vortex
that represents a velocity singularity. Here, we provide an extensive spectral
analysis of both the tabletop acoustic black hole and its higher-dimensional
gravitational analog. We find that quasinormal modes and quasibound states
share qualitative similarities in both systems and show that the eikonal
quasinormal modes of the analog acoustic black hole have a photon-sphere-like
interpretation, which points to the existence of a phonon sphere in the analog
black hole. Our results, complemented with the recently calculated graybody
factors and Hawking radiation of the acoustic analog, can provide a theoretical
test bed for future tabletop experiments with condensates of light in a
mirror's cavity and provide significant insights regarding classical and
quantum phenomena in higher-dimensional black holes.
