About 15 years ago, I started noticing that my hearing had changed. It was subtle, but every sound I heard was as much as 30 degrees off from its source. I first noticed it turkey hunting. I still have good hearing, but my left year is a bit attenuated more than the right-- probably a slight case of trucker's ear. Thirty-some years of driving with the window down will do that to you, I guess.
After I recognized the problem, I made sure I was extra careful with my hearing. I now do things like mow grass with gun muffs. Most of all, I stopped trusting my ears to tell me exactly where stuff is coming from.
Last season, for the first time, I noticed that my son was able to hear gobbling far off that I can no longer hear. It's normal aging, but it still sucks.