  It is well known that the observed amplitude of solar oscillations is lower
in sunspots than in quiet regions of the Sun. We show that this local reduction
in oscillation amplitudes combined with the phase-speed filtering procedure in
time-distance helioseismic analyses could be a source of systematic errors in
the range of 5 - 40% in the measured travel-time anomalies of acoustic waves
around sunspots. Removing these travel time artifacts is important for
correctly inferring the subsurface structure of sunspots. We suggest an
empirical correction procedure and illustrate its usage for a small sunspot.
This work utilizes data from MDI/SOHO.
