A high-pitched buzzing system has been used to help reduce trouble from teens in Leicester.
For months the owner of a takeaway in Swinford Avenue, Eyres Monsell, had been experiencing problems, prompting local police to trial the device.
The 'mosquito device' was attached to a wall near the shop and only younger people, with their more sensitive ears, can hear its persistent whine.
Officers have reported no more incidents since the trial began.
PC Paul Faithfull, neighbourhood beat officer for the Eyres Monsell neighbourhood, said: "I feel that the trial has gone well so far.
"There were always large groups of youths loitering around this area before and it is amazing how dramatically the numbers have decreased since the mosquito device was fitted.
"The owner hasn't experienced any problems since it was installed and local residents visiting the shop generally feel a lot safer."