Did you know that as you get older you lose teh ability to hear really high pitch sounds?
If you are a teenager, you will probably be able to here the sound linked to below. if you are old, you probably cant hear it. thats cause your hearing degrades as you get older so you cant hear it if your old.
To test it, listen to it, and then find someone older or younger adn see if they can hear it (a parent or a child is a great test subject)
its pretty amusing when you can hear it and others cant.
It works as a great ringtone if you are a student cause most teachers cant hear the sound, so only you and your classmates will know that your phone is ringing.
Listen Here
I can hear the sound, can you?