Do you recognize this sound? My husband tends to make this noise in his sleep. He is a very noisy sleeper. This was also part of a Seinfeld episode where either Elaine or a boyfriend made this noise when they slept and it drove the other one crazy. I can confirm, IT DRIVES ME CRAZY! If you are not understanding how it sounds, let me try to explain - breath in through nose, keep lips closed, hold air in for only a second, then PUH, force/push out the air between your lips, resulting in the PUH sound rushing out.
I guess it's not enough that I have to listen to this on a fairly regular basis, coming from the other side of the bed. Recently, I had a client who fell asleep during his massage. Not only did he PUH, but prior to the PUH he snored instead of quietly breathing in through his nose. It went like this: snore, PUH, snore, PUH, snore, PUH. To make it even more entertaining, it was a couples massage. The other therapist and I were doing all we could not to laugh out loud. And usually, when one of the clients snores in the couples room, the other client tells them to stop, or they giggle, or they make a comment. In this case, the wife didn't utter a sound. I guess she's used to it and was able to tune him out, unlike us two giggling therapists.