If others on a call (Skype, SIP, ...) can not hear you loud enough, your volume levels are probably too low. Also, Skype may be changing your mixer levels.
pavucontrol
).Switching your microphone on and off using the hardware switch on your headset's cable will cause a clicking sound, which is too loud for Skype's taste (while it actually is not that bad) -- Skype tries to compensate for that by reducing your recording volume, which causes your voice to be recorded too silent.