[DB]

Actually I don't think that is true, but I could be wrong.

If you abuse your ears, the highs go first. Also with age the high end goes first.

Most people can't hear 18 kHz when they're in the 30's. 9 kHz to 18 kHz is one octave. While that isn't good loosing the upper octave of your hearing, it isn't very serious either. The biggest impact with be enjoying music which shouldn't be severe.

[drlevy88]

Highest key on a conventional piano = 8261 Hz.