The Mosquito

The Mosquito or Mosquito alarm is a machine used to deter loitering by emitting sound at high frequency. In some versions, it is intentionally tuned to be heard primarily by younger people. Nicknamed "Mosquito" for the buzzing sound it plays, the device is marketed as a safety and security tool for preventing youths from congregating in specific areas. The latest version of the device, launched late in 2008, has two frequency settings, one of approximately 17.4 kHz that can generally be heard only by young people, and another at 8 kHz that can be heard by most people. The maximum potential output sound pressure level is stated by the manufacturer to be 108 decibels (dB) (comparable in loudness to a live rock concert) and the manufacturer's product specification furthermore states that the sound can typically be heard by people below 25 years of age. The ability to hear high frequencies deteriorates in most humans with age (a condition known as presbycusis), typically observable by the age of 18.