As the following picture shows, I have set the microphone volume to the maximum possible, but the volume recorded is very low despite putting the microphone very close to my mouth and speaking loudly. I do not have this problem with the internal microphone. And this external microphone works properly under Windows.
I don't have an answer, but I just added a USB webcam to my Xubuntu 20.04 desktop system and used it for the first time on a Zoom call. I kept manually setting the mic volume to 100% in the Pulseaudio volume control and then a few minutes later it was reset to a very low setting. This kept happening repeatedly. Any idea why the volume would auto-adjust downward and how to stop this? This is with a Larmtek W5 webcam. I'm posting here as it seems possibly related.