Although it is the world's biggest metropolis, Tokyo is not an Action News kind of town. If television news here played by the rules of big American cities ('It bleeds, it leads'), there would be little to cover. Shootings are exceedingly rare. Most people don't lock their bikes. Lost wallets are returned. The chronic paucity of mayhem in a metro area with 35 million people helps explain why several TV news crews have been skulking in the shrubbery at a kiddie park on the northern fringe of Tokyo. By Tokyo standards, Kitashikahama Park in Adachi Ward is a crime-infested hellhole. Thirteen acts of vandalism have been committed there in the past year. Toilet seats and windows have been broken. Spent firecrackers have been found. Some residents living near the park have lost sleep. The perpetrators, still on the loose, are believed to be neighborhood teenagers, probably in junior high school. Ward officials called a meeting in the spring to stop the madness. Japan's largest newspaper, the Yomiuri Shimbun, broke the news of their historic decision in late May: The park would fight teen crime by assaulting teen ears. Authorities rented a British-made Mosquito MK4 Anti-Vandal System and screwed it into a wall not far from park toilets. The device emits a high-pitched, highly irritating whine that has a frequency above 17 kilohertz. Most adults cannot hear it, but teens can. Seven days a week, the whining begins at 11 p.m. and continues until 4 a.m. Video surveillance cameras monitor park buildings. And Kitashikahama Park empties out. Except the television news crews. 'We see them on the surveillance videos, and there are too many of them to count,' said Haruyuki Masuda, head of park management in Adachi Ward. 'They hide behind trees and bushes. They are waiting for kids to come. I think they have scared off the kids.' Neighbors report that the park has quieted down at night, if you don't count the television news trucks and the TV-news-watching busybodies who descend on the park after 11 p.m. to find out whether they are too old to be irritated by the whining. 'I have seen seven television news crews, and I have been interviewed three times,' said Chiaki Takizawa, 24, who lives near the park. 'But teenagers don't come so often to make noise, and that is good.' It is too soon, however, to say that the park is safe. In late June, when TV news crews happened not to be hiding in the bushes, someone punched a hole through a toilet in the women's bathroom, apparently with a baseball bat. Surveillance video showed six or seven teenage boys loitering near the bathroom around 3 a.m. It was not clear whether their ears were hurting. Police have yet to make an arrest. Masuda said he and his staff will wait a full year before assessing the effectiveness of the Mosquito MK4 and deciding whether to install the device in other parks. 'We hadn't planned on this being a news sensation,' he said. 'We need things to calm down before we can decide if it really works. We need the TV crews to stop sneaking around.' -- Special correspondent Akiko Yamamoto contributed to this report. 