Depends on the situation. Somewhere like a loud bar or a party the noise actually helps. Probably relates to having to shout, and shouting being a somewhat different type of speech (akin to singing, I guess). But if it's a normal noise situation but there's suddenly something loud on the TV or radio, my stuttering gets worse. I'm sure there is something psychological happening here, a subconscious worry that the other person will get distracted and stop listening to me in mid-stutter, only propagating the disfluency due to anxiety. Don't know-- worth considering. And white noise does nothing but help.