It's a natural thing that happens to the inside of our hearing Corij .... When we wear headphones at too high a volume/pitch our hearing hairs get thrown around and damaged both short-term and long-term.
Try starting your next hunt at much lower volumes (so your hearing has not had an initial bombardment) and you'll find that after half an hour the lower volume is very easy to pick up and detect with, and as the hearing hairs aren't affected at all, you won't have any problems later in the day or future hearing impairment.
Once your'e used to detecting at low volume it's much more enjoyable to hunt short and extended hours. You won't miss anything and you'll find a whole new world of comfortable sound to ride with.
http://www.dangerousdecibels.org/virtualexhibit/2howdowehear.html