The Mosquito or Mosquito alarm is an electronic device used to deter loitering by young people by emitting sound at high frequency, in some versions so it can only be heard by younger people. The devices have attracted controversy on the basis of human rights and discrimination concerns.
The device is marketed as a safety and security tool for preventing youths from congregating in specific areas. As such, it is promoted to reduce anti-social behaviour such as loitering, graffiti, vandalism, drug use, drug distribution, and violence. In the UK, over 3,000 have been sold, mainly for use outside shops and near transport hubs. The device is also sold in Australia, France, Denmark, Italy, Spain, Germany, Switzerland, Canada and the USA.
Critics say that it discriminates against young people and infringes their human rights, while supporters argue that making the Mosquito illegal would infringe the rights of shopkeepers who suffer business losses when "unruly teenagers" drive away their customers. Mosquito distributors have said that they keep standards to ensure that the device is not abused, and Howard Stapleton who invented the device has asked European governments to legislate guidelines governing its use.
The newest 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). The sound can typically only be heard by people below 25 years of age, as the ability to hear high frequencies deteriorates in humans with age (a phenomenon known as presbycusis).