and this is what i found how much of hearing damage can cost by long period of riding....
(Article form internet) Back in 1994 two ear specialists from england conducted a hearing test on 44 Grand Prix riders to determine if they suffered from NIHL (noise-induced hearing loss). Almost half of them showed hearing losses much greater than the median for each one's age. "so what?" you say. "I'm not a GP rider." No, but note that this test was conducted in 1994, long before unmuffled MotoGp four-strokes ever made an appearance; muffled two-strokes with a 102-decibel-A (dBA) limit were the mount of choice back then. It was soon determined that the sound responsible for the riders' hearing loss was wind noise. And this was with the latest, trickest, most aerodynamic helmets, many with custom parts for each rider to ensure the best fit.
The two specialists, Andrew Mccombe and J. Binnington, then conducted a very thorough scientific study in 1995 of British street motorcyclists, including the country's motorcycle police. By inserting a tiny microphone next to the rider's ear they were able to measure noise levels accurately, part of which allowed them to determine that wind noise begins to drown out all other sounds once the rider passes 40 mph. At 100 mph, the wind noise level averaged at least 110 dBa for the 10 different helmets measured, which is about the same as listening to a gas-powered chainsaw (and this is with a helmet-imagine how loud it must be without one). Even cruising at 70 mph, wind noise would be about 100 dBa, which OSHA (the federal occupational safety and health administration) noise exposure standards state you can tolerate for a maximum of two hours per dayand that's cumulative, not per exposure-before permanent hearing damage definitely occurs. part of Mccombe and Binnington's study involved having a group of 18 selected riders go through a rigidly controlled test, and all were found to have suffered measurable hearing damage.
"Big deal," some of you are surely saying. "I've been riding for 10 years without earplugs and can hear fine." The problem is that the damage to your hearing is insidious; the most vulnerable parts of your ear are the receptors that handle the higher frequencies of sound that aren't readily noticeable. Everyone has surely experienced temporary hearing loss from deafening noises in the lower frequencies such as fireworks or loud concerts; after an hour or so your hearing returns, giving the impression that permanent hearing loss would involve the same massive deficiencies across the complete hearing frequency range. Unfortunately, noise-induced hearing loss from continued exposure occurs in a much more subtle way. The lost higher frequencies involve the minor inflections of speech that help define spoken language, especially consonants that don't have the louder vocal intonations of vowels, often occurring as the difference between past and present tense or singular and plural. For example, if someone were to speak in a normal tone of voice and environment, would you be able to tell the difference between "happen" and "happened" or "sportbike" and "sportbikes"?