Recording only above a certain dB level

I feel this is a relatively simplistic thing to do but haven’t been able to find it anywhere. How do I make sure audacity only records above a certain dB level? I know you can do Sound Activated Recording but once recording is activated then it records all sound. Thanks

It is possible with digital trickery, but the results sound computery, see …

Audacity can’t split a mixed recording into individual voices, instruments or sounds.

If the goal is to read for audiobooks and you can’t pass noise, there are tools, ways and techniques to fix that.