Hum is often caused by lack of proper electrical ground. For this problem, we’ll use multiple modules in a particular order to mitigate it. The De-hum module in iZotope’s RX noise reduction software includes a series of notch filters that can be set to remove both the base frequency of the hum (usually 50 or 60 Hz), as well as harmonics that may have resulted. Then we can use the Spectral De-noise module to address additional buzz above those harmonics.
Here is an example of dialogue track with the significant 60 cycle hum in the background, as well as harmonics and buzz extending far above the fundamental.