Using ReaFir in Reaper to create a noise floor profile can reduce constant background sounds such as whistles, whines, buzz, traffic noise, fan noise, hiss and hum.
It’s a simple tool that can make a night and day difference to a noisy track.
- Find a spot in the offending track where there’s a good 10-20 seconds of the background noise you want to eliminate. Then set up a loop for that section of the track.
- Load up an instance of ReaFir. Set the Mode to Subtact and tick Automatically build noise profile.
- Play the section of audio. ReaFir will build a profile for the background noise.
- Press the Spacebar to stop playback and un-tick Automatically build noise profile, hold the Command key (Mac) or CTRL key (Windows) and drag the EQ curve (noise profile) down a dB or two, I find this leaves less artefacts.
- Find a place in the track where the instrument is playing and resume playback. Boom! The noise is gone.
Experiment with how much you drop the gain of the EQ curve by, you’ll find it produces different results for different instruments.
In general I find a 1 to 2dB reduction produces amazing results on a noisy guitar or bass signal and what noise is left is undetectable in the mix.