  The statistical behavior of the eigenvalues of the sample covariance matrix
(SCM) plays a key role in determining the performance of adaptive beamformers
(ABF) in presence of noise. This paper presents a method to compute the
approximate eigenvalue density function (EDF) for the SCM of a \cin{} field
when only a finite number of shapshots are available. The EDF of the ensemble
covariance matrix (ECM) is modeled as an atomic density with many fewer atoms
than the SCM size. The model results in substantial computational savings over
more direct methods of computing the EDF. The approximate EDF obtained from
this method agrees closely with histograms of eigenvalues obtained from
simulation.
