How Good Is Your Hearing?

Tonight I was sitting here innocently reading the current issue of Winging It when this horrible high pitched sound attacked my ears. I about jumped out of my skin. Non Birding Bill was playing a sound file of a silent ring tone that teenagers are using on their phones to secretly send text messages. The frequency is so high that adults aren't supposed to be able to hear it. NBB couldn't hear a thing, but I could. Try out the link, can you hear it?