Cooper Menvier has acquired the marketing and manufacturing rights to crowd dispersal system 'The Mosquito' from inventor Howard Stapleton's company Compound Security Ltd.

The Mosquito generates a high frequency sound that is audible only to teenagers. Cooper Menvier says this is "completely harmless even with long term use, and rarely affects older people as it relies on a medical phenomenon known as presbycusis, or age related hearing loss.

"With an effective range of between 15 and 20 metres, field trials have shown that teenagers are acutely aware of the Mosquito and usually move away from the area within just a couple of minutes.

"The ultrasound produced has no effects on pets or other animals and can safely be used in all public areas, businesses or domestic premises."