  We derive expectations for signatures in the measured travel times of waves
that interact with thermal anomalies and jets. A series of numerical
experiments that involve the dynamic linear evolution of an acoustic wave field
in a solar-like stratified spherical shell in the presence of fully 3D
time-stationary perturbations are performed. The imprints of these interactions
are observed as shifts in wave travel times, which are extracted from these
data through methods of time-distance helioseismology \citep{duvall}. In
situations where at least one of the spatial dimensions of the scatterer was
smaller than a wavelength, oscillatory time shift signals were recovered from
the analyses, pointing directly to a means of resolving sub-wavelength
features. As evidence for this claim, we present analyses of simulations with
spatially localized jets and sound-speed perturbations. We analyze 1 years'
worth solar observations to estimate the noise level associated with the time
differences. Based on theoretical estimates, Fresnel zone time shifts
associated with the (possible) sharp rotation gradient at the base of the
convection zone are of the order 0.01 - 0.1 s, well below the noise level that
could be reached with the currently available amount of data ($\sim 0.15-0.2$ s
with 10 yrs of data).
