carlo, regarding household sounds, when zachery was about a month old, we discovered by accident that he would be very soothed by the sound of the kitchen sink running. in fact, that then became the only way we could get him to fall asleep (walking back and forth in front of the running sink), and has continued, almost to this day, to be our cue to him that a nap is coming.

it's basically stopped working just recently, but for the longest time, that was our little bedtime routine.