We mothers tiptoe around our babies when they are asleep so as not to wake them up. During the evenings, I won't let anyone flush the loo, watch TV, talk too loudly or wash up. I have also unplugged the phone on occasion, even though it's totally out of Betty and Dolly's earshot.
Last night our smoke alarm went off, ringing continuously for about 10 seconds. It's practically next to Dolly's head, and she didn't even flinch, let alone wake up.