原创 How well is your hearing?

I stumbled upon a device called The Mosquito a few years back. It uses ultrasonics to get rid of unwanted groups of teenagers.

This is actually quite an interesting concept when you come to think about it. The motivation for creating this device is that crowds of teenagers hanging around store fronts are the bane of shopkeepers around the world. The idea behind the Mosquito is that our hearing starts to deteriorate when we turn 20 years of age, with the higher frequencies going first. The result is that it's possible to generate an annoying high-frequency sound that is audible only to teenagers.

In fact, even for those who can just hear this sound, it's not a problem if you are walking into or out of a store. It's only if you hang around for a few minutes that it starts to become annoying. Apparently, field trials have shown that teenagers usually move away from a Mosquito-protected area within just a couple of minutes.

When I first ran across this I remember thinking that it might even be useful for use at home; now that my son is 16 years old ... I'm sure of it (I'm only joking, he's actually got a great bunch of friends, which is a huge weight off my mind).

But we digress... it seems that the boot is on the other foot, as it were, because I just ran across a site called Mosquito Ringtones. This site allows teenagers to play various frequencies to determine the highest one they can hear; for example:

 8kHz Pretty much anyone can hear

 10kHz 60 and younger

 12kHz 50 and younger

 :

 18kHz 24 and younger

 22kHz 18 and younger

The idea is that the teenager downloads a ring tone to their phone such that the ring tone's frequency is so high that most adults cannot hear it. I just tried playing with the site – it was scary to discover that 12kHz is the highest frequency I can hear (I'm soon to be 54—but at least I have the ears of a 50-year-old [grin]).

If I were still a teenager, of course, I would think that this was a jolly clever idea – no more problems with your parents saying "I told you no calls after 9:00pm," because they wouldn't even know you were receiving a call. You could simply excuse yourself from the room and then return your friend's call (I'm certainly NOT going to mention this blog to my son).

I tell you ... just when you think you have finished learning new things for the day ... you learn something new (Really? I can't hear anything above 12kHz ... that was a bit of a surprise...)