Perhaps you've heard about the ultrasonic ringtone? It's one of those neat synergies that James Burke would be proud of. A few years ago, someone discovered that the range of human hearing narrows with age, and deduced that there were, therefore, tones that teenagers could hear which adults couldn't.

The initial use of this was something very different than what we ended up with. The first thing that came to mind was that they could play this tone in front of convenience stores, annoying the hell out of teenagers, and thereby discouraging them to hang out there, while being inaudible to good-natured adults. Of course, the tone wasn't physically painful or anything. Nor was it even really that annoying; it was just bothersome enough that it made te front of the store a place you wouldn't want to go unless you had a good reason.

But it didn't take long before the teenagers worked out a way to use their superhuman hearing to their advantage: these frequencies, rendered into a ringtone, would allow them to receive calls which adults would not be able to hear. (Now, before you point out that the technology to make a phone indicate that an incoming call without alerting anyone else nearby already existed, I'm going to remark that I called my beloved on her cell phone the other day, and she had to rush off to answer it. The cell phone was set to vibrate. And inside her car. Halfway across the parking lot). This is a boon to kids who want to receive calls in school, where such things are forbidden (Where I went to high school, being caught with a cell phone was an expellable offense. You didn't just have it confiscated: you were sent to the office and the police were called in to arrest you. This was a silly outmoded law dating from the days when owning a pager was considered a 100% perfect indicator of being a drug dealer).

Anyway, I went to a webpage and listened to some sounds, and it guessed my age:

I imagine I should be a little offended.