A Christchurch library has taken a novel approach to fighting crime - it's using a device designed to emit an annoying sound that can only be heard by young people, generally anyone under 25.
Christchurch City Council head of libraries and information Carolyn Robertson said the "mosquito" device had previously only been used at night in the foyer of Papanui Library.
However, after a physical assault outside the library and complaints about large groups of youths gathering outside it, intimidating customers, the decision was made to use it during the day as well, she said.
She said recent feedback suggested the device, which cost $1350 plus GST, was helping to manage that behaviour.
"Customers say there has been an improved atmosphere at the library and praised the use of the initiative as they feel once again the library is a lovely place to be."
Acting Sergeant Nick Adcock said the majority of young people respected Papanui's local facilities, but police were aware there had been some problems around the library.
"There have been reports of people feeling intimidated by these groups loitering around out there," he said.
Shirley-Papanui councillor Pauline Cotter said the device was not the right approach to the problem.
"I don't like the fact that we are producing this high-pitched noise that apparently only they [young people] can hear it, but it's a very horrible sound and I wonder if even it's breaching a human rights issue actually," she said.
"I feel sorry for the library staff and the other users of the library, absolutely. But there must be a better way."
Sam Phan's Cambodian restaurant is next door to the library, and he said he had been forced to call police several times in the past because of young people.
He said he would like a device to use outside his own business.
"I see a lot of young kids, hanging around the library and our shop, just smoking and spitting around [the area] and it's just disgusting," he said.
Mr Phan said they sometimes blocked the entrance to his restaurant, and had caused a loss in income.
The council said it would continue to monitor and evaluate the use of the device, which was not as yet being used at other council facilities.
Ms Cotter said the community board would be discussing the issue at a meeting next week.