Ideally, if you have a nice low noise floor (virtually no sound when you’re not speaking) and good dynamic range (large difference between the quiet and loud parts, where the louder parts punch Audacity’s Recording Level into the yellow or orange), you shouldn’t need to use Audacity’s Noise Removal function. Every time you use an Audacity effect, your recording and voice will sound a little bit less natural, so we always want to keep these transformations to a minimum. Noise Removal can be particularly damaging to the audio, because it involves removing part of the sound.
However, there are cases just like with the Compressor and Normalize functions, where Noise Removal does more good than bad. Use Noise Removal if:
You are having trouble getting the Noise Floor (“RMS Tr dB” in SoX) below ‑60dB.
You are having trouble keeping the Average Volume (“RMS lev dB” in SoX) at -20dB or higher without pushing the Noise Floor up above ‑60dB. This indicates insufficient dynamic range.
Even if your file technically passes the Noise Floor and Average Volume requirements, you believe there is consistent background noise in parts of your recordings that you’d like to remove.
In these cases, Noise Removal can help by removing background noise, increasing dynamic range, and further quieting the quiet parts. Here’s how:
Perform Noise Removal BEFORE applying other effects, such as Compressor or Normalize.
There must be about 2 seconds of quiet (no talking) recorded that includes the background noise you want to remove. If the noise is just electronic noise, this is easy because it’s probably always there and doesn’t change much. If it’s something else, like a jackhammer drilling outside your window that only runs sometimes, then you need to make sure to capture about two seconds or more of that noise.
