When you bite something in two pieces, e.g. a piece of hard candy, you hear the sound through two sources: vibrations in the air, entering your ears from the outside and internal vibrations in your skull.
What I have noticed is that there is a difference in (the way I perceive*) the sound intensity when my ears are plugged with in-ear phones or earplugs, as opposed to the unplugged case. The thing that surprises me is that the sound actually seems louder (higher intensity) WITH my ears plugged. I would expect the sound to be less loud because I am blocking part of sound waves with my earplugs.
My question is whether there is a physical explanation for the higher intensity with plugged ears? Some form of resonance perhaps? Or is it really just perception?
* I mention perceived, because I can also imagine that it is some physiological effect in which the baseline of what I perceive as low and high is changed by the lack of sound coming in from the outside. If that is the case then physics.se is probably not the right place to ask this question