  Rapidly oscillating Ap stars are unique objects in the potential they offer
to study the interplay between a number of important physical phenomena, in
particular, pulsations, magnetic fields, diffusion, and convection.
Nevertheless, the simple understanding of how the observed pulsations are
excited in these stars is still in progress. In this work we perform a test to
what is possibly the most widely accepted excitation theory for this class of
stellar pulsators. The test is based on the study of a subset of members of
this class for which stringent data on the fundamental parameters are available
thanks to interferometry. For three out of the four stars considered in this
study, we find that linear, non-adiabatic models with envelope convection
suppressed around the magnetic poles can reproduce well the frequency region
where oscillations are observed. For the fourth star in our sample no agreement
is found, indicating that a new excitation mechanism must be considered. For
the three stars whose observed frequencies can be explained by the excitation
models under discussion, we derive the minimum angular extent of the region
where convection must be suppressed. Finally, we find that the frequency
regions where modes are expected to be excited in these models is very
sensitive to the stellar radius. This opens the interesting possibility of
determining this quantity and related ones, such as the effective temperature
or luminosity, from comparison between model predictions and observations, in
other targets for which these parameters are not well determined.
