This could be off-topic, but I need some help and advice on how to investigate.
I've a KDE Neon and three different headphones that I can plug into my minipc jacks to record audio.
The problem is that, no matter which one I do plug, there is always a noise (~ -42 dB) coming from the microphone. What puzzles me is that if I use zoom (application) or google meet the noise is not present, but with all other tools that access to the microphone (e.g., audacity) the noise is there.
I've tried to configure alsa using all the available sliders in alsamixer, but no matter how I configure the sound is either too low or the noise is too high.
I'm using latest neon on ubuntu 20.04.

In kde control panel I don't found anything else than a single "internal microphone". Switching from alsa to pulse make the microphone not able to record at all (no noise, no sound). If I ask alsa to list devices I see this is Intel PCH, and all modules (sndcore, ecc.) seems to be loaded.
Any suggestion?