The fact that I HAVE to listen to something to be able to isolate myself from my surroundings is pretty depressing to me, specially because I don't like listening to music for long periods of time.
Try http://asoftmurmur.com/ - it's meaningless ambient noise that I find quite effective as audio wallpaper.
I also recommend noisli.com, I use it everyday, saw it here in HN a couple months ago. It's great for concentration IMO, instead of music, which I just ignore or some times distracts me.