If your audio level is well above the noise level, you can simply use a noise gate.
If the noise level is too high or there are too many gaps in the audio (creating an obnoxious on/off pumping of noise), you need to filter the noise by creating a fingerprint or sample from the noise and then process the audio so that the fingerprinted sample is extracted. Such a process can be made with various tools, such as Wavelab. There are other tools, but I am not aware of any that are free.
This is the Audition forum, right? I thought the answers posted here would have to do with how to fix the problem in Audition. Is there a video that shows how the hum can be eliminated in Audition? I have used Audacity already, and it did no good. Its not riding over the voice, its just plainly there in the audio. Ideas?
Well, Jim, some of them will, some of them won't - I think Stefan was just trying to be helpful. In Audition I generally find a clear spot where there is only noise, then use Capture Noise Print, which grabs only the noise. Then I save that, and remove it from the master clip; it takes a bit of experimentation to know how agressively you need to apply it. There's a walkthrough of your options here: