Troubled sleep

My wife has bought this fancy gadget that makes a variety of noises designed to make the baby go to, and more importantly, stay, asleep. It has an option of birds twittering, rain falling, wind rustling leaves and so on. The one she favours is supposed to be waves crashing on a beach. However, to me it sounds like a rottweiller sleeping, albeit it with one eye open. So everytime I go past my son's room at night, I hear this monster heavy breathing in there. To be fair though, it does make him sleep. But I'm pretty sure it's out of fear more than anything.