The Mosquito Tone

The story of the Mosquito Device, the Mosquito Tone, and Teen Buzz ringtones.

The "mosquito tone" is a nickname for a sound that is devised to be so high-pitched that only younger people can hear it. As people age, they gradually lose some of their hearing (a phenomenon called presbycusis), and their hearing naturally loses sensitivity to higher frequencies. So the older you are, the less likely you are to be able to hear higher frequency sounds (or, the louder they will need to be before you are able to hear them).

The Original Mosquito Device

In 2005, a Welsh inventor named Howard Stapleton created a device that took advantage of this phenomenon. He developed a tone that was designed to be undetectable by most people over 25 yet easily heard by most people under 25. In addition, he modulated the tone in such a way as to make it highly annoying. The purpose of the device was to discourage teenagers from loitering around businesses, schools, and certain public areas, where some teenagers were hassling or robbing customers or vandalizing property. The patented invention is called the Mosquito Security Device, and it is marketed by the UK company Compound Security Systems.

The original tone developed for the Mosquito anti-loitering device has a frequency of about 17.4 kilohertz (kHz). In reality, of course, there is no magic cut-off at age 25; some people under 25 are not able to hear it, and many people over 25 can. However, almost everyone under 20 with normal hearing can hear it, and the vast majority of people over 30 cannot, and that is why this particular frequency was chosen.

The Kids Turn the Tables: Mosquito Ringtones

Teenagers quickly realized that they could make use of this phenomenon as well and put it to their advantage. They created high-pitched ringtones for cell phones that they could hear but older adults could not. In classrooms and other situations where the use of cell phones was forbidden, they could surreptitiously receive a signal for an incoming phone call or text message, a signal which in most cases could not be heard by the (older) teacher or supervisor.

These "silent" ringtones, sometimes called "Teen Buzz" ringtones, are usually simple sine waves, without the modulation of the original Mosquito tone that adds an annoyance factor. They can be at any frequency that can be heard by the user of the cell phone; a typical frequency is 14.4 kHz. (At higher frequencies, some cell phones aren't capable of playing the sound loudly enough to be useful.) Although the somewhat lower frequency makes it more likely that an adult may be able to hear the sound, it is normally audible to adults only at close range or higher volume. High-frequency sounds are also easily shielded; even turning your head can render a sound inaudible.

Read more: Can you hear the mosquito tone?

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