I was about an hour into the shroom trip and he was peaking. Things were getting a little tight in the muscles and jaw. He sat up on the couch, and adjusted his ear canals (like a SCUBA pop), and he heard this strange second-long "oooOOOIK". It was weird and high pitched, starting soft and got louder. It was what you would expect a stressed tendon to sound like (from inside the tendon) - hard to define. He hadn't heard it before, and hasn't heard it since. It didn't sound like air pressure equalizing. It was almost electric sounding. Anybody else ever experience anything like that?