Noise, Cotton Balls, Ears and Music
Unlike most commercial earplugs, which are designed to attenuate sounds by 20 to 40dB, a small wad of cotton stuffed into the ear canal provides only about 10dB of attenuation. The absorption varies smoothly with frequency from about 5dB in the bass up to a maximum of 15dB in the highs.
If you listen to a heavy-metal rock concert at 115dB for an hour, you'll certainly experience TTS or some ringing in your ears, but you'll probably recover the next day. But if you expose yourself to those levels for several hours every day, your loss may be severe and permanent. Some of the most famous rock musicians have learned this lesson the hard way.
When you're thirtysomething you cease being annoyed by the 15.75kHz whistle emitted by the horizontal flyback transformer in every TV set. And now that I'm fortysomething, many of my compatriots no longer hear much above 10 or 12kHz.
If you spend too much time shooting guns, driving sports cars, occupying a front-row seat at heavy-metal rock concerts, or playing oboe in a symphony orchestra while sitting directly in front of the first trumpet, the first sign of permanent damage is that you start asking everyone to repeat what they just said.
For a simple test, try wearing cotton plugs for an hour or two before a critical listening session, especially while driving to a concert or audio store. Take them out when you arrive, and see whether the resulting freedom of TTS enhances your perception.
But note that audiograms, which only extend up to 8kHz, do not test your upper-frequency hearing limit. You can use the test tones on our Test CD 2—track 27, index points 30 to 37, which cover frequencies of 8kHz, 10kHz, 12.5kHz, 14kHz, 15kHz, 16kHz, 18kHz, and 20kHz—to check for yourself where you can no longer hear the tone.
http://www.stereophile.com/asweseeit/cotton_balls_amp_delicate_precision_instruments/