This "mosquito ringtone" is the original "secret ringtone." A secret ringtone is any ringtone which is recorded above 15Khz.
Most adults are unable to hear frequencies above 15Khz due to age-related hearling loss known as presbycusis. Because of this, secret ringtones such as the mosquito ringtone can usually only be heard by people up to their mid twenties.
This sound was originally developed by Howard Stapleton of Compound Security Systems as a way to prevent young people from loitering around businesses. That product was named the Mosquito, because the sound it creates is like a very large swarm of mosquitos. The original Mosquito sound was recorded at 17Khz. This sound can be very annoying to those that can hear it and does work quite well for its intended purpose.
Someone decided to copy this sound and use it as a mobile phone ringtone. This ringtone gained popularity because most schools require that cell phones be turned off. With the mosquito ringtone, very few teachers are able to hear a students cell phone ringing.
Paradoxically, something that was developed to annoy teenagers has become extemely popular with teenagers.
Another popular secret ringtone is the Teen Buzz ringtone, which is recorded at a lower 14.4Khz frequency.
Download the Mosquito Ringtone.