Honestly, I cube better with people around. No idea why: I set my 2nd best PB (29.33) at school when I was in the middle of class, just on the computer (on CubeMania.org) when I was discussing with a bunch of people what games in 2009 would be cool enough to buy for my laptop when I go off to uni...
I set my 26.42 when I was in the CAFETERIA on a friend's laptop; everyone was like "WTF" around me, knowing I'm usually a 45 second guy; I told them that it was non-lucky (had to explain what that meant) and that the F2L cases were actually quite simple (I built an x-cross accidentally, one edge-pair was built by that time, I saw the other two and moved them into position WHILE I WAS INSERTING THE FIRST ONE, and the OLL was 1-look; not hard... Stupid PLL though, it was both adjacent corner swap + a stupid adjacent edge swap, yes I use 2-look because I'm a newbie).
I also get sub-40 averages when I listen to music, usually Linkin Park or In Flames -- I got my FIRST sub-40 average when I listened to the ENTIRE Come Clarity album, and my 35.61 (of 5) was achieved when Take This Life was playing...
So in a way, I NEED NOISE; else I suck.

(notice how in EVERY ONE OF MY YOUTUBE videos I can't get a sub-30, since there's no noise)