Audacity Noise Reduction

• Constant background sound in a recording: hiss, hum, whine, buzz, air conditioning or fan noise

• Not for one-off sounds such as a door slam or clicks and pops, or for irregular noise such as traffic or an audience
• Needs a stretch of the recording that holds only the noise, to learn its profile; if that stretch includes your voice, the filter eats into it
• May not give a good result when the noise is very loud or changes, or when the voice is not much louder than the noise
• Pushed too far, it leaves metallic, watery artifacts; a modest reduction that leaves some noise usually sounds better

Select a few seconds of noise only → Effect → Noise removal and repair → Noise reduction → Get noise profile; then select all the audio to clean → Noise reduction again → set the sliders → apply

The noise test hears your mic the way your browser gets it, which may not include Audacity Noise Reduction. Run it to see how much noise your mic picks up, so you know how much the filter has to remove.

It works on audio you have recorded and opened in Audacity, not on a live call.