I had this squeak in my shoe that really drove me insane.
At first, I didn't notice it much. Maybe I'd be walking down an echoing hallway or passing though some quiet area. Suddenly, I'd become aware of the squeak. It was a squelching, squishy sort of squeak, not overly loud, but subtly invasive. On carpet, it sometimes sounded as if the rug’s fabric was soaked through with some viscous or unclean liquid, making me want to see if I needed to clean the bottom of my shoe.
After the first few months, I began to notice the squeak more and more frequently.