In the bang chamber at greater heights communication is the last thing possible. Your pressure clothing inflates and so does your gullet. For non pilots you concentrate on breathing out. Pilots have to do that and initiate a 10,000 fpm descent.
Even if you could talk you could not hear as your ear drums are literally as taut as a drum. Your vision is probably degraded with oxygen blowing from your tear ducts.
At 43,000 feet the oxygen system on the Black Buck aircraft was at a lower pressure than its maximum which would have been deliver ed at 50,000 ft. Their next problem with the door open would be the low temperatures.