My diaper made a hissing noise the other day, but I wasn't peeing. Then snakes started popping out, hundreds of them and I said, "I'm some damn f**king sick and tired of all these f**king snakes in a diaper!!!!
I know what you're talking about. Sometimes I don't even realize that I've started going until I feel the wet sensation down there. It's just the way it is I guess because for many the bladder/sphincter muscles weaken as we age. But once in a while I have a hissing full-bladder voiding that reminds me of how satisfying relief can be.
It is not heard as much as I pee in the diaper, but I have a broad plump butt and when I will sit on a soaked bloated diaper then you hear a muffled lengthier creaking sounds and the 4 extra pillows I have inside my diaper will slowly be squeezed into a thin stamp.
I never realized that hissing sound was actually a thing, I thought it was just a convenient fiction used in diaper stories. I can't remember ever hearing or making any noise in reality short of liquid hitting porcelain...