Noise Removal
From Audacity Manual
Noise Removal can reduce constant background sounds such as hum, whistle, whine or buzz, and moderate amounts of "hiss". It is not suitable for individual clicks and pops, or irregular background noise such as from traffic or an audience. To use the effect, select some audio which is representative of only the noise. Audacity then tries to remove sound that matches this "noise profile".
Step 1
- Get Noise Profile: This first step identifies the type of sound you want to reduce. Select a region of the waveform which only contains that noise, then click Get Noise Profile.
Step 2
- Noise Reduction: The amount of noise reduction to apply. Small values usually work better. If you set this too large, the audio you want to keep is usually significantly affected too. It's generally better to reduce the background noise a bit than to try to remove it completely.
- Frequency Smoothing: The larger this value the more that the effect considers different frequencies as "the same". If your noise is a single frequency such as mains hum or a high pitched whistle, then keep this value small. If your noise is more like a hiss, then a larger value will generally be better.
- Attack/decay time: How quickly noise removal reacts. Use a larger value if the background noise is pretty constant. Use a smaller value if it varies rapidly.
The technically minded might like to read a description of the noise removal algorithm used on our main Wiki.
