I have the standard perfect prep machine (the one which beeps) and have just bought a second hand Day and Night one off eBay for upstairs. We used it for the first time last night and could not believe how loud it was (I'm referring to the running of the machine itself when administering water). Apart from being able to silence the beeps it is definitely louder than my original - have I bought a dodgy machine here, or is this model generally louder when it's running? All reviews online say how quiet it is so I was really surprised last night, and still ended up waking the rest of the family!