TOKYO: A restroom for women at a Tokyo park has been vandalised, in a setback for an unlikely experiment to stop youngsters from roaming around at night and causing damage to public property, by installing a loudspeaker system that emits an offensive high-pitched frequency.

The frequency cannot be heard by those over 40, even at close range, but the vandalised facility appears to have been blocked by a wall.

It was the first time any facility in Kitashikahama Park in Adachi Ward had been vandalised since the May 21 kick-off of the experiment, which uses a "mosquito whine" typically audible only to those in their teens or early 20s.

According to the section in charge of the park at Adachi Ward Office, a worker on Sunday discovered a hole in a toilet at the women's restroom.

It appeared to have been made with a baseball bat. Used rocket fireworks were also found nearby.

The toilet is next to the park's administrative office, where the British-made sound-emitting device is installed.

However, it is understood that the noise - which is directed towards the entrance of the men's restroom - is barely audible inside the women's restroom as it is blocked by a wall.

The device has a range of about 40m. Melc, the Japanese agency which distributes the whine emitter, has sold over 20 of the devices in the past year, mostly to convenience stores.

The park was the first local body to install one.

The ward office examined imagesrecorded by a surveillancecamera in the park and foundthat six or seven boys had beenplaying in the park for 10 minutesat about 3am on Sunday. -Yomiuri Shimbun/ANN

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