I'm older than most of you guys. Years ago, I spent a lot of time around loud live rock music in nightclubs and in concert settings. I'm talking 120db or greater. I also flew small single and multi-engine airplanes that have loud cockpit noise. For both of these loud noise situations, I never used any ear protection. I didn't use ear protection when shooting guns or operating power tools either. As a result, I now have hearing impairment. It's not really hearing loss the way one would think, but it affects me when there is loud ambient background noise, like music, noisy restaurants, sporting events, etc. When someone next to me is talking, I barely hear them and only understand the 3rd or 4th word, or I don't hear them at all and just see their lips moving. Others, who are the same distance away, however, hear the person just fine. It's worse when trying to hear people with higher pitched voices, which most women have. In situations where there is no background noise, I hear like normal.
The hearing impairment I have is not a horrible thing but it can be quite annoying when I'm really trying to hear and I can't. If I knew back then what I was doing to my hearing, I would have used ear protection like I do now. I also need to mention that this condition didn't show up until years later. I've been to 3 ear doctors and done my own research and I am positive the cause was from being around loud noises. I've never had any ear problems, such as ear infections, my entire life. There is no cure, and doctors say the problem will continue to get worse as the years go by.
I now use those little spongy earplugs. Just roll them between your fingers to squish them, insert them in the ear, and they expand to fill the shape of the ear canal. They work extreemly well. If the noise is loud(110db-120db), but not really loud (120db+), I pull them out of my ear a little to make them slightly loose. This still cuts the highs & dampens the noise spikes, but allows for normal hearing. Plus for my impairment, the use of these earplugs, in loud background noise environments, allows me to hear the person next to me, where without the plugs, I couldn't.
So to answer your question, I don't think that if you listen to music at 150db, that you will be deaf when you are 18, but I do think you will begin to have hearing problems in your thirties like I did. And it will get worse in your forties, like it's doing to me. Do your own research on this subject, there is plenty of information available. Back when I was doing damage to my ears, nobody was talking about ear damage or using hearing protection. It's because of guys like me who over-exposed their ears to loud noise years ago, that they now have this medical condition to examine, study, write about, and give warnings about. We didn't know about Aids back then either. Use protection.
'89 K5 Silverado 4" lift w/BFG 33's