I seem to recall something in college that spoke about the human ear being able to "push back" against sound pressure levels that it found uncomfortable. It might be interesting to go a web site about such topics and see if this could be a factor (the situation you are describing). I am not certain how this could be, but I think it has to do with the tiny bones in the inner ear that provide the linkage to the eardrum. In any event, don't rely on your sound pressure meter, do as Garfish says (and perhaps as your ears are warning) turn it down a bit and save them for the long term.
