  We use a publicly available numerical wave-propagation simulation of Hartlep
et al. 2011 to test the ability of helioseismic holography to detect signatures
of a compact, fully submerged, 5% sound-speed perturbation placed at a depth of
50 Mm within a solar model. We find that helioseismic holography as employed in
a nominal "lateral-vantage" or "deep-focus" geometry employing quadrants of an
annular pupil is capable of detecting and characterizing the perturbation. A
number of tests of the methodology, including the use of a plane-parallel
approximation, the definition of travel-time shifts, the use of different
phase-speed filters, and changes to the pupils, are also performed. It is found
that travel-time shifts made using Gabor-wavelet fitting are essentially
identical to those derived from the phase of the Fourier transform of the
cross-covariance functions. The errors in travel-time shifts caused by the
plane-parallel approximation can be minimized to less than a second for the
depths and fields of view considered here. Based on the measured strength of
the mean travel-time signal of the perturbation, no substantial improvement in
sensitivity is produced by varying the analysis procedure from the nominal
methodology in conformance with expectations. The measured travel-time shifts
are essentially unchanged by varying the profile of the phase-speed filter or
omitting the filter entirely. The method remains maximally sensitive when
applied with pupils that are wide quadrants, as opposed to narrower quadrants
or with pupils composed of smaller arcs. We discuss the significance of these
results for the recent controversy regarding suspected pre-emergence signatures
of active regions.
