if I start twinkle (voip app) and gnome-sound-recorder at the same time, and set both to record (that is: call an echo test SIP number from twinkle, and hit record in g-s-r) then g-s-r records my voice at normal volume perfectly, and twinkle doesn't hear any sound from me unless I shout. This is using the internal mic: no external mics are plugged in.
Updated information:
if I start twinkle (voip app) and gnome-sound- recorder at the same time, and set both to record (that is: call an echo test SIP number from twinkle, and hit record in g-s-r) then g-s-r records my voice at normal volume perfectly, and twinkle doesn't hear any sound from me unless I shout. This is using the internal mic: no external mics are plugged in.