I’ve read that high sound levels in headphones can make things sound lower-pitched than they really are, so I’m always sure to keep my headphones at a moderate level. But I’m having a hard time confirming that’s really true.
Edit: I found a diagram at the end of this slide series that shows how intensity affects pitch. The whole series is interesting though. http://www2.bcs.rochester.edu/courses/crsinf/221/15.pdf
Interesting. But why do they say this: "Pitch is subjective, and cannot be measured directly" - I mean, what is a guitar tuner doing, if not directly measuring pitch?