As you get older there are certain high frequencies you can no longer hear. One particular frequency is called a "Mosquito Tone", which is near or at 17.4 kHz. Most people over the age of 25 cannot hear this tone. I’m 34, and I can’t hear it.

A few years back a device called The Mosquito was introduced specifically to solve teen loitering problems in front of stores. It emitted the 17.4 kHz tone that could be heard from about 140 feet (43 meters) away, and sure enough it worked great.

The device was so successful it won a Nobel Prize.

I know what you’re thinking. "I want to hear this tone." No problem. You can download samples of the sounds here. Just scroll down and check it out for yourself. MP3 and WAV versions available. There are also other tones to test how much you can still hear. I suggest starting with the 8 kHz and go from there.

Remember: Keep the volume low when listening to these. These tones (even the 8 kHz one) will make you say, "WOW, that’s annoying.."

To those of the do-it-yourself vein that would like to make a "teen repellent" of your own, you could use the tone, burn it to a CD and play it using a portable "boom box" with the track repeated. However there are a few immediate problems.

First, anyone under 25 can hear it – including small children.

Second, if you have pets, it may drive them nuts. It may also drive other animals away.

Third, some adults over 25 can still hear the sound.

If you want to use it, do so with caution.