If someone were pounding away loudly at an IBM selectric typewriter, I probably wouldn't notice it at all. When I take a test, I don't hear anything, and I don't "see" anything outside the test booklet, and accessories (calculator, pencil, etc.) I con turn the entirety of my mind to focus on important things, but really only if they are mentally challenging enough.
A construction crew was tearing up the floor in my highschool for half a year, and it was quite easy for me to not notice the sound of the jackhammer outside the doorway.
I don't know how the Bar exam goes, but others typing and being loud wouldn't bother me at all.