i can tell you there is back ground noise.
Other people are taking other exams, not just the usmle step 1. So there will be fingers hitting keyboards and such. You can use the headphones to block out noise. They really do work. There will be constant humms from the comptuers and the airconditioner.
now that your freaking out more, you must be getting closer to your exam. Study, know that you've done everything you can to pass the exam, continue to study hard and have a positive attidude.
I was 2 hairs from cancelling my exam because I was freaking out but I said "this is all that can be done, I can't do anything else or learn anymore". I took the exam and passed.
You can do it.