  This paper presents an analysis of observational data on the p-mode spectrum
of the star alpha Cen B and a comparison with theoretical computations of the
stochastic excitation and damping of the modes. We find that at frequencies >
4500 micro-Hz, the model damping rates appear to be too weak to explain the
observed shape of the power spectral density of alpha Cen B. The conclusion
rests on the assumption that most of the disagreement is due to problems
modelling the damping rates, not the excitation rates, of the modes. This
assumption is supported by a parallel analysis of BiSON Sun-as-a-star data, for
which it is possible to use analysis of very long timeseries to place tight
constraints on the assumption. The BiSON analysis shows that there is a similar
high-frequency disagreement between theory and observation in the Sun.
  We demonstrate that by using suitable comparisons of theory and observation
it is possible to make inference on the dependence of the p-mode linewidths on
frequency, without directly measuring those linewidths, even though the alpha
Cen B dataset is only a few nights long. Use of independent measures from a
previous study of the alpha Cen B linewidths in two parts of its spectrum also
allows us to calibrate our linewidth estimates for the star. The resulting
calibrated linewidth curve looks similar to a frequency-scaled version of its
solar cousin, with the scaling factor equal to the ratio of the respective
acoustic cut-off frequencies of the two stars. The ratio of the frequencies at
which the onset of high-frequency problems is seen in both stars is also given
approximately by the same scaling factor.
