  We performed 3D numerical simulations of the solar surface wave field for the
quiet Sun and for three models with different localized sound-speed variations
in the interior with: (i) deep, (ii) shallow, and (iii) two-layer structures.
We used simulated data generated by two different codes which use the same
standard solar model as a background model, but utilize two different
integration techniques and use different models of stochastic wave excitation.
Acoustic travel times were measured from all data sets using the time-distance
helioseismology technique and compared with the ray theory predictions,
frequently used for helioseismic travel-time inversions. It is found that the
measured travel-time shifts agree well with the ray theory in both cases with
and without phase-speed filtering for the shallow and deep perturbations. This
testing verifies the whole measuring-filtering-inversion procedure for
sound-speed anomalies inside the Sun. It is shown, that the phase-speed
filtering, frequently used to improve the signal-to-noise ratio does not
introduce significant systematic errors. Results of the sound-speed inversion
procedure show good agreement with the background sound-speed profiles in all
cases. Due to its smoothing nature, the inversion procedure overestimates sound
speed variations in areas with sharp gradients of the sound-speed profile.
