Headphones (and ears) question

A few months ago my crappy headphones broke so I replace them with a set of Sony MDR-V250’s. Not a great set, and a few annoyances, but not a bad solution for the price.

The problem I’m now noting is that when I use them for an hour or more, the apparent volume (i.e. what I’m hearing) seems to slowly drop. The headphone volume control is maxed and though I start out my mp3 player at 50%, I seem to be constantly increasing the volume. By the end of an album I’m up to 75% or higher volume.

One thing I noticed when I first got these was that the high volume on the headphones was relatively lower than on my previous set (in other words, with the mp3 player set at 50% the old set of phones could get much louder than the new ones.)

So, could this be a problem with the headphones? With the mp3 player? Or is it my ears?

Ears or player are most likely, with my bet on ears.

I vote ears, too.