I don't really yawn with my mouth closed, but just tried mimicking it and yes, same sound as long as I tense the top of my jaw under my ears. It's more or less

I don't really yawn with my mouth closed, but just tried mimicking it and yes, same sound as long as I tense the top of my jaw under my ears. It's more or less the same the same tone as closing your ears manually by pushing the tragus over the opening with your finger, but a bit louder for me.