  Recent photometric observations of massive stars show ubiquitous
low-frequency "red-noise" variability, which has been interpreted as internal
gravity waves (IGWs). Simulations of IGWs generated by convection show smooth
surface wave spectra, qualitatively matching the observed red-noise. On the
other hand, theoretical calculations by Shiode et al (2013) and Lecoanet et al
(2019) predict IGWs should manifest at the surface as regularly-spaced peaks
associated with standing g-modes. In this work, we compare these theoretical
approaches to simplified 2D numerical simulations. The simulations show g-mode
peaks at their surface, and are in good agreement with Lecoanet et al (2019).
The amplitude estimates of Shiode et al (2013) did not take into account the
finite width of the g-mode peaks; after correcting for this finite width, we
find good agreement with simulations. However, simulations need to be run for
hundreds of convection turnover times for the peaks to become visible; this is
a long time to run a simulation, but a short time in the life of a star. The
final spectrum can be predicted by calculating the wave energy flux spectrum in
much shorter simulations, and then either applying the theory of Shiode et al
(2013) or Lecoanet et al (2019).
