It's kind of funny that we are just starting to realize the need for hearing protection now when close ups of rock bands show that many of the players were wearing ear plugs years ago.
In spite of having run engines from 020 to 35 without mufflers for almost 15 years before going into the air force, I still had mostly normal hearing according to my hearing charts. After 4 years on a flight line working around ground support equipment with 150 to 200 hp unmuffled engines, SA-16s, F100s, F105s, F-4s, C-130s, KC and RC97s, my chart looks like a cross section of the floor of the pacific ocean. Luckily, by the time I got in, not wearing ear protetion on the flightline was a court-martial offence.
Some of the club members used to make fun of one old-timer who always wore ear muffs while starting and adjusting his engines. Took them off when the plane was in the air. A former Contol line speed and racing pilot from before mufflers were even readily available. Sharpest ears in the club at 75. He could hear sounds that even some teens can't.
Few of our mufflers do enough sound reduction to spare us from damage from long term exposure.