Upper panel: iron abundance profiles used in four, otherwise identical, test models. The black, red, blue, and green curves correspond to the profile at diffusive equilibrium between gravitational settling and radiative levitation, the profile when the amount of levitating iron is decreased by a factor of two, the profile after a decrease of a factor of four, and the profile assuming a uniform iron distribution in solar proportion. Lower panel: corresponding profiles for the Brunt-Väisälä (solid curves) and Lamb (dotted curves for l = 1 and l = 2) frequencies.