Topic: Noise Reduction Procedure with RX

[voltronic]

After much trial and error with Izotope RX the last couple years, I have arrived at what I feel are the most transparent-sounding noise reduction settings for what I record (acoustic / classical).  Below is the procedure I follow as my starting point for post processing any time I'm recording this type of music in a hall with HVAC or other steady background noise. 

My settings are only a suggested starting point, but I thought I'd share in the hopes that it will save others some time and frustration.  Also, my suggestions will definitely not eliminate background noise, but should help to reduce it significantly without causing audible artifacts.

1. Start with the "Rumble Reduction" preset, make sure it's set to Spectral / Manual, and grab your noise profile.  Make sure you have the Spectrogram view enabled to help you find the quietest section of hall noise.

2. Activate the "Reduction Curve" (this step is quite important I've found).

3. Set quality to D (best) and leave all other settings alone.

4. Tweak the Reduction Amount until it reduces the noise acceptably without starting to sound unnatural. I try not to go higher than 6-12, as the higher you go the more likely you are to introduce artifacts. In the choir recordings I do, I start to get artifacts on the consonants if I go much beyond 6-9. I err on the side of slightly more noise in the results, if it means the music sounds more natural. To my ears the "processed" sound of too aggressive noise reduction is more distracting than the noise itself.

5. Alternate previewing as normal vs. through the "output noise only" setting while you work so you're not grabbing the parts of the audio you want to keep.  If you are listening with "output noise only" active and it sounds like you're listening to your music through a concrete wall, you know you've gone too far!

I've found RX to be the only tool that I can get acceptable results with this sort of thing. It's quite amazing what it can do, but for those of us who have to record in such places it's still a challenge. Good luck!