I know we’ve seen this topic in the pub before, but somehow this came up again at our house:
Here’s a fun game you can play with your kids. Download the “ringtone” on this page. Then play it when your kids (pretty much anyone under 25 or so qualifies) least expect it. They’ll scream at you.
(As if you needed a way to elicit that response.)
http://www.npr.org/templates/story/story.php?storyId=5434687
Ouch! It makes my ears itch. It gets right into your brain and is like an itch you can’t scratch. Horrible. It freaks the cats out too!. (and I’m quite a bit older than 25…or 30, or 35…that’s as far as I’m prepared to go!!). 
We have a lot of bats outside in the summer months. I can always hear them, but my husband and friends can’t.
Cass.
I’m 41 and I can “hear” it. (I don’t know if “hear” is the right word but I can certainly and immediately detect it as it makes me instantly feel ill.)
Horrible is a good word for it.
–James
Yeah, OK…I admit it…I’m 41 too!
Cass. 
Mere babies! I’m way past that, and my right ear makes its own ringtones, 24X7. (It’s called tinnitus). More squealing drones, I just don’t need.
Who am I to complain, though? Today’s car stereos are doing more damage than my 70’s rock concerts ever could. Free advice: Buy stock in hearing aid companies, and hold it for about twenty years! 
Buy stock in hearing aid companies, and hold it for about twenty years!
My eldest daughter and her husband just bought a hearing aid franchise!
They are counting on us baby boomers …
Whaa???
That’s interesting. Quicktime plays it, and if I turn the volume up I can hear it. It doesn’t irritate me or make me sick. (On the other hand I’m feeling slightly sick today anyway. )
Microsoft Media Player doesn’t produce any sound that I can hear, even with the volume turned up.
I’m in my fifties. I get tinnitus too. And the b*stards have turned the gravity way up today. Grrr.
Great, I’ve got a headache now. Bloody old people 
::maniacal laughter::
I can hear it, but Mr Izz can’t. Go fig. It really is a diabolical noise 
I can’t hear it, but if I get close to the speaker I feel pressure in my head.
People now sell speakers that play this sound to keep teenagers from hanging out in front of convenience stores. A while ago there was a story on Slashdot about a crochety old man installing one on his house because he hated kids.
It was an interesting legal question of whether you can get busted for violating a noise ordinance in a range inaudible to the cops. The Slashdot consensus was to just saunter by the speaker one day and stick a knitting needle through the speaker cone. After all, the crotchety old neighbor can’t hear if it isn’t working.
Caj
I’m one of those crotchety old folks who can’t hear the slightest thing in either Windows Media or Quicktime. Faint drones are particularly annoying to me, though. Others don’t hear them and they give me headaches. My old laptop had a distinctive sound few others could hear. Drove me half-crazy! (The other half was already there.)
Edited: When played inside the player, I can hear it. When played in a stand alone player I cannot. It sounds about like the frequency of my old laptop.