I'm 33 now, and I've been going to the races ever since I can remember. Let's say I can remember 29 years worth. I was never one to always have a Sony Walkman playing heavy metal in my ears constantly. And noise from racing really didn't start to bother me until just a couple of years ago.
I was raised with dirt track racing. Sprint cars & late models, so I've heard plenty of Small Block Chevys at 8000 rpms on up. Noise at the dirt track doesn't bother me, until the cars gets scattered out like when the leader catches lapped traffic to the point where there's always a car in front of you.
NASCAR races depend on the track. Noise didn't bother me at Daytona, Pocono, or Charlotte but it did bother me at Dover and Richmond. Smaller tracks, noise stays confined.
Nitro engines produce to me the most beautiful sound on Earth. I stick my fingers in my ears only during a full throttle pass, or right before the throttle whack during a warmup. Under idle, doesn't bother me. Alky cars rattle my ears some during a run, and during the high rev part of the warmup. A PS or PM engine is loud when your directly behind the car, but during a run, it doesn't bother me.
Sitting near the starting line at any drag race after a whole day will give me a headache from the noise.
Long story in short, I wish I had taken better care of my hearing.