  In this brief note, we pursue the systematic investigation of possible
gravitational wave sources in the gigahertz band. We focus on hyperbolic
encounters of light black holes and evaluate precisely the expected signal when
accounting for the detailed characteristics of haloscope experiments.
Considering the GraHal setup as a benchmark, we insist on the correct
signal-to-noise ratio expression taking into account the appropriate
timescales. The associated maximum distance - of the order of a few hundreds of
astronomical units - at which an event can be detected is calculated for
optimal, sub-optimal, and general trajectories.
