In an important finding following questions about its potential effects on hearing, the Belgian Superior Health Council has concluded that the high frequency pulsating sound presents no danger to adults and youths.
The physical “annoyance” felt by youths were consistent with the intention of the device, said the group.
But the group adds that the effect on babies and small children is unknown and long lasting exposure should be avoided. In unborn babies it was unlikely that much of the energy would be absorbed.
The group also concluded it was unlikely the Mosquito would be effective on a long term basis because it produces a stimulus that people usually get accustomed to.
There was also a risk that it was seen as a provocation and could lead to aggressive behaviour.
The Belgian Superior Health Council conclusions come after a year of debate over whether or not the devices used – mainly by retailers – to reduce vandalism and anti-social behaviour are harmful to health.
The Mosquito produces a high frequency (16-20kHz) pulsating sound that is, in practice, audible only by youths. The sound pressure changes according to how close it is to the subject.
When it is switched on it goes through a cycle, including 20 minutes of no sound. Setting methods can be manual, via a timer or detector.
In a document (published in French and translated by the UK supplier, Compound Security Systems Ltd) the group conclusions included both physical and “pychosocial” effects.
Physical effects
The group listed the effects of high frequency sound “in general” on a person’s health. These were “aspecific” or “temporary effects including headache, hearing high pitched noises, exhaustion, dizziness and nausea”.
It concluded that, “based on the available data” there was “no danger for hearing loss for adults and youths as a consequence of exposure to the Mosquito sound.
“Aspecific complaints can arise which is consistent with the function of the devise, eg, annoyance in youths.
“The effect on babies is unknown. Therefore long lasting exposure of small children and babies should be avoided.
“There are no scientific studies on possible damages of the produced sound to the foetus. Taking into account the reflection and absorption of the high frequency sound in the air and the attenuating consequences of the different surfaces/tissue (air, mother’s tissue, foetal water, ear foetus) it is unlikely that a lot of energy will be absorbed by the foetus’ ear.
“In terms of the impact on people inside surrounding buildings, high frequency sound will, on the one hand, be reflected strongly by walls, windows and other building materials. On the other hand it only has a limited depth of penetration.
“Consequently, effects on occupants (such as sleeping children/babies) should not be feared.”
Psycho-social effects
Despite the lack of scientific evidence on the effect of Mosquito on the psycho-social health of youths, the experts reached a number of important conclusions.
“It is very unlikely that Mosquito is effective on a long-term basis, since it is an aversive stimulus that people usually get accustomed to.
“In addition, there is the risk that Mosquito is seen as a provocation and leads to aggressive behaviour. A better alternative would be to create meeting places for youths.
“In conclusion, it was pointed out that this is also an ethical debate, and before the ethical debate can be held, the problem should first be defined properly.”
The working group looking at the physical effects included experts in sound physics, biology, medicine and environmental health. The group looking at the “psychosocial” aspects included specialists in psychology, psychiatry and sociology.
* There are said to be some 3,500 devices in use in the UK, mostly by retailers and the police. The device is typically heard by people younger than 25 years of age because the ability to hear high frequency deteriorates over time.
* Compound Security Ltd has now launched a “Music Mosquito” – a self contained “mood calming system” which plays classical or chill-out music. The company says it is in response to some users who have felt they are no longer able to use the conventional Mosquito “due to local public youth pressure”.