  Seismic waves can couple with the atmosphere and generate sound waves. The
influence of faulting mechanisms on earthquake sound patterns provides
opportunities for earthquake source characterization. Sound radiated from
earthquakes can be perceived as disturbing which can negatively impact the
social acceptance of geoengineering applications. Motivated by reports of felt
and heard disturbances associated with the week-long stimulation of a 6 km-deep
geothermal system in 2018 below the Otaniemi district of Espoo, Helsinki, we
conduct fully coupled 3D numerical simulations of wave propagation in the solid
Earth and the atmosphere. We assess the sensitivity of the ground shaking and
audible noise distributions to the source geometry of the induced earthquakes.
Utilizing recent computational advances and the open-source software SeisSol,
we model seismo-acoustic frequencies up to 25 Hz, thereby reaching the lower
limit of the audible sound frequency range. We present synthetic distributions
of shaking and audible and discuss implications for better understanding
seismic nuisances in metropolitan regions. In five 3D coupled elastic-acoustic
scenario, we analyze the ground velocity and pressure levels of
earthquake-generated seismic and acoustic waves. We show that S waves generate
the strongest sound disturbance with sound pressure levels of up to 0.04 Pa. We
use statistical analysis to compare our noise distributions with commonly used
empirical relationships. We find that our 3D synthetic amplitudes are generally
smaller than the empirical predictions and that the interaction of the
source-specific radiation pattern and topography can lead to significant
non-linear effects. Our study highlights the complexity and information content
of spatially variable audible effects associated with small induced earthquakes
on local scales.
