The 'beep's, 'pop', 'screech' and ocassional screams ("No" is pretty popular, for some reason) happen randomly, and I don't know that they can be "recreated". You can reach the right state for them at the onset of trance or at it's outset, but there is no guarantee they'll happen- or when.

A side comment, not meant to derail-
I think "no" is the subconscious way of startling you out of the trance, but I don't really think it is threatened (like many speculate. I don't think the subconscious can be threatened)- I think it's a matter of how much the subject uses the word in waking life-a habit.