Maybe you had no choice but to record in a noisy environment. Maybe your refrigerator, radiator, fan, or similar noise generating device snuck it’s way onto your recording without you realizing it. Either way, you’ve got a recording to clean.
First, open Reaper and create a new track (left click on the left side of the screen and select Insert new track or use Ctrl-T).
Next, insert your media into that track by selecting Insert -> Media file. . . or pressing the Insert key on your keyboard. Lead the dialog box to the file you’d like to clean and click OK. You should be able to see your noisy file with the track you just created.
Then, click on the little FX button on the track head to open the add FX dialog box.
Click Add and navigate to All Plugins -> Cockos -> ReaFir and click OK. You may see more than one version of the plugin, select either.
Once ReaFIR pops open on the screen, put it in Subtract mode. This tells ReaFIR to listen to, and then remove, any audio you put through it.
Scan through the audio file and find a spot without any content. The only thing you should be able to hear is the noise you are trying to eliminate. While you should use your ears, enlarging the track view might help you find the intermittent noise. Click on the track head and press Page Up on your keyboard to expand the waveform vertically.
Look for as long a sample of the noise as you can find. Loop the area you’d like to target by clicking and dragging the mouse at the top of the track view (where you can see measure/beat and timecode markers) and engage the loop function. This will give you a continuous loop of the area you’re working with and will ensure that you don’t feed ReaFIR any audio that you want to keep.
Check ‘Automatically build noise profile’ on the ReaFIR plugin window and start playback. ReaFIR will then build a noise profile based on whatever audio you had highlighted. You’ll see the graphic analyzer that represents the sound move around. The yellow line represents the audio coming through the ReaFIR plugin, the red line represents the noise profile it builds from that audio, and the dark yellow or brown line represents audio that has been subtracted from playback by the noise profile. Over the course of a couple seconds, you’ll see the red line stabilize and the bright yellow line disappear completely.
Stop playback and uncheck ‘Automatically build noise profile’ in ReaFIR (otherwise ReaFIR will continue to scan, and then subtract, the actual content). Disengage the loop function and resume playback; you will hear altered audio.
Much of the noise from your clip should be gone. To fine tune the removal Ctrl-Click the jagged red line and move it up (to allow more noise) or down (to remove more noise) with the mouse. Be sure to Ctrl-Click, as a regular click will manually draw a new noise profile. If that happens, or if you think you can get a better picture of the noise you want to remove, click ‘Reset’ and start again.
Please note that if any recorded content you don’t want cleaned out passes through ReaFIR while Automatically build noise profile is checked, ReaFIR will make that audio part of its noise removal profile and eliminate it along with anything else. If that happens, just deselect Automatically build noise profile, click Reset, and start again.
You’ll have to use your ears to determine how much noise removal is appropriate. Too much removal and the content will start to sound muffled or develop a watery, sloshing sound. Too little removal and too much of the noise will remain. Try to eliminate as much noise as you can while maintaining the integrity of the original content.