  We present an intrinsic metric that quantifies distances between power
spectral density functions. The metric was derived by the author in a recent
arXiv-report (math.OC/0607026) as the geodesic distance between spectral
density functions with respect to a particular pseudo-Riemannian metric
motivated by a quadratic prediction problem. We provide an independent
verification of the metric inequality and discuss certain key properties of the
induced topology.
