You know what, i've always wondered this myself.
I literally cannot process noise either. It's almost as if my startle reflex is hyper-sensitive. If there's a loud noise (even if I know it's coming) I cannot cope.
I can only speculate that with BPD we're "hyper-sensitive" anyway, and so it would only make sense that some of our other senses are the same.
Does it make a difference if you're tired at all? Because I know with chronic fatigue this is an issue, and I find when i'm tired and have to deal with noise I literally feel like i'm going to have a heart attack (I know that sounds dramatic, but it's unbearable).
It'll be interesting to see if others reply to this with the same experience.