system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If you were travelling faster than the speed of sound, what would happen if you screamed?

I know it seems irrational, but Felix Baumgartner! Thanks 😊

EDIT: Thanks everyone for all your replies :). Loving reading them! Just like to add, I know this can't happen without special clothing etc., like what Baumgartner wore, or being in a pressurised compartment such as a cockpit. I'm just wondering, theoretically ;). Thanks again :).
gpt
In a pressurised compartment or spacesuit or something, the air between your mouth and ears isn't moving relative to you, so things are normal. If the air is moving past you faster than the speed of sound, (either you or the air can be moving) the sound from your mouth may not be able to travel through the air to your ears.  
You might still hear something due to sound waves propagating through your bones, but it's more likely that you'd not because the air around your head would be pressurised by ram pressure and probably deafen you. 
This reasoning may well be invalid because air behaves differently when it is hitting your face at hundreds of metres per second to when it is unimpeded.