Hey, there. I recently recorded a wedding, where the MC's microphone had a few problems. In particular on a few occasions he positioned the microphone in way as to cause positive amplification of the signal. (Similar to what you hear if you bring the microphone very close to the speakers).
I have tried to use the usefull signal as noise sample and run Audion's noise removal to keep only noise, but it has not worked that well.
The other thing I have tried was to try and user Graphical Equalizer to try and decrease the volume of the frequency that the noise is running on. However, that altered the original sound to the point that it was no longer usable.
Any other suggestiong would be greatly appreciated.