The admonition to protect our hearing would be more useful, if it were possible, but it basically isn't possible.  Infants can hear 30,000 herz.  Tom Scott here, who looks to be in his 30's, can no longer hear 15,000 herz, but that is not a natural effect of aging.  Wizened Bedouins in the desert have been shown to be able to hear 30,000 herz, just like toddlers.  What we think of as our "natural" hearing loss as we age is nothing but the cumulative effect of the noise pollution that pervades our modern, probably urban, environments.  So, short of moving to the Falklands, there is nothing we can do to prevent hearing loss.<br><br><br>I could still hear the 15,000 herz whistle from a CRT when I was 40, but not since.