The Mosquito, a relatively new invention developed by Compound Security in the UK, does sound like a bit of a joke, something from Chris Morris's Brasseye perhaps.

Designed to stop teens and young people congregating outside business establishments, it emits two modulating tones that are of a frequency that most people over 25 can no longer hear.

For those who can hear it, the sound is so annoying that would-be delinquents (and more harmless youngsters) have to move along. So far, so fantastical. But it's all good science.

"There are hairs inside the ear which resonate and relay sounds into the brain and the hairs that resonate at high frequencies die off the older you get, " explains Simon Morris of Compound Security, the British company that manufactures the Mosquito.

"Normally by the time you are 25 you have lost the ability to hear above 14 kHz and we take advantage of that by using two tones one at 17-anda-half kHz and one at 18-anda-half and it flicks backwards and forwards about four times a second. If we were to use a constant tone the brain would be able to filter it out."

According to Simon, the annoyance factor builds only if people stick around at the front of the shop. Staff members inside the shop can't hear it, and for customers of any age, simply passing by the Mosquito isn't a problem.

In other words, it won't deter genuine customers, and to comply with safety and noise pollution regulations, the Mosquito mark II goes on for only 20 minutes at a time and at a maximum level of 95 decibels (house alarms can go up to 130db).

The Mosquito was invented by Howard Stapleton to assist a friend and neighbour who was having problems with anti-social elements near his shop. Stapleton had his eureka moment when he remembered how, when visiting a battery factory as a child, he alone in a room full of adults could hear the unbearable sound coming from one of the machines.

The Mosquito has been on the market in Britain since last year, and is being sold in Ireland by Les Devlin of Devlin Retail Systems (www. devlinretailsystems. ie).

Devlin has been selling it for three months now and has noticed a huge upswing of interest in the last six weeks.

The Mosquito costs 1,195 excluding VAT and installation, and there are already 30 live sites in the Leinster region. Devlin estimates that another 15 will go up over the next week.

"I think a lot of people like it because it removes confrontation, " he says. "You don't have to deal with or talk with these kids. They just move on. Management companies and residential units, factories, blocks of apartments are putting them up.

One guy who has a car park is putting it up."

Of course it could be a case of the emperor's new clothes.

How do you know it's even working if you can't hear it yourself? Dave Lawless from the Templeogue Inn has doubted it himself.

"Sometimes I have to get one or two of the younger staff to go check that it's on because I can't hear it at all, " he says. But he has also witnessed it operating over the past two weeks.

"We have a porch entrance on the way into the pub and you could have ten or 15 kids standing in the porchway after school, " he says. "They were littering, they were blocking fire-doors, and we were getting complaints from older customers that they were feeling intimidated coming into the pub. At that time we would have the older clientele coming in to have something to eat, and older people do feel intimidated by having teenagers standing in their way."

So Lawless joined the increasing numbers of people who have resorted to sonicwarfare, and he hasn't looked back. "We used to get 15 to 20 people loitering there a day.

Now we get one at most."

Another of Les Devlin's happy customers is Andre Van Zyl, who manages a Spar in Castleknock. Van Zyl had a similar problem with schoolkids congregating and littering at the entrance to his shop at lunchtime and after school. When I contacted him on a Friday he had just installed the device but was unable to give me any verdict. When I called around at lunchtime on Monday, a grinning Van Zyl showed me there wasn't a dawdling adolescent in sight.

"When I put it on, on Saturday you could see them wondering what it was, " he says. "Two of them actually came in and asked me to turn it off! They all moved off very quickly. A couple of them tried to be stubborn and hang around but they moved on as well."

Of Van Zyl's staff, only a younger worker called Thomas can actually hear the device, but luckily it doesn't affect him in the shop. "It's a horrible sound. I can understand why they move on."

All of this testimony made me eager to test the Mosquito myself. I play in a band, so I decided that a good place to test it would be to broadcast it to an audience at a gig. Midset I explained to the 100 or so people present what I was doing. So I put down my guitar, put the machine on, put the microphone up to it andf nothing. Well, for me there was nothing. One very audible voice in the audience was shouting: "For God's sake turn it off!" A headcount afterwards showed that 50% could hear the annoying buzz and 50% could hear nothing (corresponding, I'm guessing, to those under 25 and those over 25). The poor fellow who had been shouting was a little shell-shocked.

"That was horrible, " he said.

So it's not a great way to retain fans, but the people who use the Mosquito aren't worried about that. They just want anti-social elements to go away. Many of these antisocial elements are young and the Mosquito gets rid of young people.

And it's not just businesses that are interested. Les Devlin has sold Mosquitos to housing estates and has recently had interest from local councils. Meanwhile, in Britain, 1,500 of the devices sold were to local councils and police. But are there wider ethical issues? Compound Security is adamant that there are not.

"We've spent an awful lot of money with some of the top human rights lawyers in the country and there are no issue with human rights, " says Simon Morris. "We've examined health and safety with top UK consultants.

We've examined environmental legislation. There are no issues with its use at all."

Mary Cunningham, director of The National Youth Council of Ireland, however, is not so sure about this. As well as having doubts about the safety of the device, she also thinks the Mosquito might not survive a challenge under equality legislation.

"Obviously the big issue for us is that this is very discriminatory against young people, and therefore I believe it contravenes the equality legislation on age grounds, " she says. "It's discrimination but it's also indiscriminate discrimination, in that it's targeting the whole age cohort.

It won't necessarily prevent anti-social behaviour; it's just going to send young people from one place to another.

The real problem is that young people need appropriate facilities where they can hang out. This measure is an infringement of their very basic human rights and will alienate them further from the adults with whom they are sharing space."

Until a challenge is made, however, the Mosquito will continue to gain popularity with retailers, home-owners, and even local government, and it most definitely puts a new spin on the term 'wicked buzz'.