External microphone input volume too quiet
The command to set your microphone levels all the way up is this:
sudo osascript -e &quot;set volume input volume 100&quot;

Also check your microphones for dust in the mic hole and if there is a power source on the device you may need to plug it in. It may need the built in mic amp.
If that doesn't help possibly a 3rd party free app like Soundsource that gives you sliders to toggle Speaker/Microphone levels from the menu bar. I've never used it but found it referenced in the apple forums.