It's actually not that noisy normally, just the clatter of keyboards.... until there are problems with something, then it can become pretty active. Most people stick with Hipchat or email for routine communications like getting stuck on debugging a piece of code or where to eat lunch -- unless they are talking in one of the break rooms, or they duck into one of the conference rooms. People tend to be pretty cognizant of the open office so if you hear people talking, it's generally something worth listening to.