  Gravitational wave observations of the near-horizon region of black holes
lend insight into the quantum nature of gravity. In particular, gravitational
wave echoes have been identified as a potential signature of quantum
gravity-inspired structure near the horizon. In this paper, we connect such
observables to the language of black hole microstates in string theory and
holography. To that end, we propose a toy model describing the AdS$_3$
near-horizon region of five-dimensional black holes, inspired by earlier work
of Solodukhin. This model captures key features of recently constructed
microstate geometries, and allows us to make three observations. First, we
relate the language of AdS/CFT, in particular the holographic retarded
two-point correlator, to effective parameters modeling the structure that are
used in flat space gravitational wave literature. Second, we find that for a
typical microstate, the `cap' of the microstructure is exponentially close to
the horizon, making it an effective sub-Planckian correction to the black hole
geometry, although the microstate geometry itself is classical. Third, using a
microcanonical ensemble average over geometries, we find support for the claim
that the gravitational wave echo amplitude in a typical quantum microstate of
the black hole is exponentially suppressed by the black hole entropy.
