We have a thin partition in the bathroom with the neighbors, and usually everyone can hear well what is happening there with them, well and vice versa. For a long time, I was cracked when someone behind the wall turned on the fan, because in that noise I began to hear some terrible silenced twists, which immediately stopped when the fan stalled. I tried for a long time to explain to myself the nature of these sounds, came already to the theory of white noise, only in my case about fan noise, and it is shameful in general to tell what I only came up with, until one day the fan didn't shut down, and the twists remained. It turned out that the neighbor was singing while drying her hair, and stuck when she cut off her dryer. Probably embarrassed.