  Helioseismic holography is a powerful technique used to probe the solar
interior based on estimations of the 3D wavefield. Porter--Bojarski holography,
which is a well-established method used in acoustics to recover sources and
scatterers in 3D, is also an estimation of the wavefield, and hence it has the
potential to be applied to helioseismology. Here we present a proof of concept
study, where we compare helioseismic holography and Porter--Bojarski holography
under the assumption that the waves propagate in a homogeneous medium. We
consider the problem of locating a point source of wave excitation inside a
sphere. Under these assumptions, we find that the two imaging methods have the
same capability of locating the source, with the exception that helioseismic
holography suffers from "ghost images" (i.e., artificial peaks away from the
source location). We conclude that Porter--Bojarski holography may improve the
current method used in helioseismology.
