I was a little afraid to try this - I remember as a teenager working in a Radio Shack; a middle aged guy came in to return speakers he just bought because he had played a test record through them at home and they did not have the advertised frequency response. So I hooked them up in the sound room and played his test record. His face fell when he realized that I could indeed hear all of the test tones...

Anyway, I was surprised to find that I still have 35 - 12,000. I was imagining that noisy environments (power tools) had probably done me more damage than that.