It is known that, for a gimbaled inertial measurement unit employing two dry-tuned gyros, a dual gyro wheel supply (DGWS) gives a better performance than a single gyro wheel supply (SGWS). The effectiveness of the DGWS is explained in this paper by demonstrating the effects of certain vibrations on gyros. It will be shown that a dry-tuned gyro is susceptible to vibrations at frequencies which are either equal to or twice that of the gyro spin frequency. By using two power supplies of slightly different frequencies, external vibrations at these frequencies are avoided. It is recommended that gyro sensitivities with respect to external vibrations at these special frequencies be included in the performance specification of a dry-tuned gyro.