I'm also the opposite. The more people that are around, the more my brain seems to turn to sludge. What I can relate to, is often times I need the TV or talk radio on in the background if I'm doing some form of productive work. It's kind of like you said - I don't need to be talking to the person, but I want someone talking in the background (preferably a radio/TV because I won't be required to talk back or interact).
Interesting. I'm in my own head so much, that I really enjoy "going out" and hearing the sounds of city life as you mention, but not for the sake of Ti. If I take a book or my laptop to a coffee shop, for instance, I just can't concentrate. I like the "buzz" around me in these places, but I'd rather just sit and casually read a newspaper and sip some coffee. I guess I'm too self aware (plus I like to people watch) to really get deep into something when others are around.
Even when I go to the library or a bookstore, I'm there only to pick out a book, not to stay and read it. I get my book, go home, close the door and read without any form of distraction. Seems to be the only way I can really take in what I'm reading in a way that I can process it clearly and make sense out of it. When others are around, I can read the book, but I'm so aware of everything else that's going on (hey there's that cute girl I saw last week!, what the heck is that guy doing?, the lady making coffee looks depressed), that it breaks up any kind of flow to what I'm reading. Maybe public outings are my chance to practice Si.