Abstract: Methods and apparatus for reducing noise in a radially ventilated rotor of a dynamoelectric machine are provided by slots formed in the pole regions of the rotor. Members formed of a selected magnetic material, having longitudinally extending ventilating ducts connected with a plurality of ventilating holes, are inserted within each slot and provided with the same flow of cooling fluid which is introduced into the slot contents of the radially ventilated rotor. Thereafter, the flow of fluid through both the slot contents and the pole regions is equalized in order to prevent flow-induced noise.