An increasing number of U.S. mall owners are adopting curfews to control teen populations at their properties. But here's an interesting alternative being tried in Canada according to the Edmonton Sun. The device, called ‘Mosquito,’ emits a high-pitched high frequency sound that people older than 25 can't hear because of natural hearing loss. Vancouver-based Dynatrac Systems Inc. bought the distribution rights for the ‘Mosquito’ from its makers, Compound Security Systems (CCS), based out of Britain.“From what I understand, it's a very, very annoying sound,” Dynatrac spokesman Michael Gibson told the newspaper.