How good is your hearing ? And how do you know ?

I remembered this article, about high-school students having their cell phone ring at a high enough frequency so the adults can't hear it:
http://www.foxnews.com/story/2006/06/13/new-york-schoolkids-use-cell-phone-ring-tone-teachers-cant-h...

I think just the opposite of inna though regarding hearing quality vs. equipment quality.  As my hearing is going down, I'm wanting my equipment quality to compensate as much as possible for it.

Of course, the other problem is when you're young and can hear perfectly, you can't afford the better equipment, so I listened on "The Record Eater" turntable.