I have tested Waves X-noise, with good results. It's an expensive and specializing bundle but it creates an annoying delay in the sound material, if not the sound program compensates for this when exporting (i.e. older versions of Pro Tools LE). Waves C4 works very well in many contexts.
How To set up Waves C4 as a four-band noise reduction processor
If you have the plugin, I suggest you read the manual for it, quite interesting. This is what I found.
You will need to use headphones and crank the volume up a lot to hear what is going on in the video.
- Find a section of audio where only noise is present, and loop it for preview.
- Listen to each band of noise separately (using Solo) and determine the amount of noise reduction you want to apply to this band. Set Gain equal to the amount of noise reduction wanted in each band (a negative value).
- Set Range to exactly compensate for the gain reduction in low levels — that is the Range should be exactly the inverse of Gain (if Gain=-12dB, Range=+12dB).
- While previewing the noise segment, set Threshold in each band such that it is just enough above the noise energy in this band, so that you hear enough noise reduction in that band.
- It will be useful here to use a hard Knee setting (set the Knee control in the Master control section to its maximum).
Now preview an audio segment where the wanted signal is present, and make sure it is indeed enough above the threshold(s) so that no gain reduction takes place (the yellow line is at 0dB gain).
Pay attention to the problematic passages, where the signal fades out or other soft sections where the audio comes closer to the noise level; careful adjustment of Threshold is required there to avoid too much degradation of the signal itself.