Last night I tried a WILD/HIT (didn't work this time), and at one point I heard something that sounded like a loud 'pop' in my room, which may or may not have originated near the outside-facing wall. I felt like I was "deeper inside my head" at that point (besides being a bit nervous because of the noise and the uncertainty of its origin), though I'm not sure if the sound was real or not.

Is this normal when trying to WILD? Or am I just going loopy? Or maybe something really did make the noise?