If people manage to be productive on a noisy, busy train by not in a quite, nice office, it isn't the interruptions that are the problem.

While I agree that steps should be taken not to interrupt people while they are working, 'quiet Thursdays' could become 'Johnny didn't get anything done because he needed to ask a question Thursdays'.

I do agree with email and IM instead of demanding that someone stop right now and pay attention to you while you phone and stare at them. No matter how urgent your question is, it can wait until someone has a natural stopping point.