Quick one, sorry if there's a thread somewhere but I can't look as dd is waking up. I know this because she's in the same room as me but we discovered last night that we can't always hear her if she's upstairs (I really don't think she's woken up very often when she's been up there and we've been down here, honest!) and it's loud down here so we need to buy one today. Are they all the same? TIA for any advice.