Mosquito Sonic Teenage Deterrant

There have been many stories in the Press / TV this week regarding the trials being undertaken of the "Mosquito" Sonic Teenage Deterrant, which is a device that generates an irritating signal at a perceived 80Db at approx 19MHz.

The claimed effect is to move on teenagers / children when they congregate in public places. They represent the latest move in the adults War against Children. When you ask the Question "OK so the device scares the kids and they go away, what do you mean by away ?" ... such devices simply metastasise the problems if unrult youth by dispersing them over wider and less public and unobservable areas.

They represent the last move of the morally bankrupt Local Authorities who starve the area of youthful enetertainment and leisure and then repress them with legal threats of ASBO's, Dispersal Orders,Parental Control orders, Truancy Fines by an army of officials of State control ranging from Youth Offending Teams to quasi Police, resplendant in fluorescent jackets and a smug bearing.... " Man proud man, dress'd in a little brief authority."

These units aimed at youth work because with age, humans experience diminished sensitivity to high frequency sounds. Youthful hearing extends as high as 20,000 Hz (Hz = cycles/second). However, the average person (especially among men) over fifty years of age has completely lost the very highest frequencies and often suffers moderate hearing loss in the range from 4,000 to 10,000 Hz. Moderate to severe hearing loss above 4,000-5,000 Hz becomes the norm for many individuals living sixty and beyond.

Loss of hearing with age, technically referred to as "presbycusis," is a widespread phenomenon that seemingly cannot be avoided. To make matter worse, prolonged exposure to loud music and other loud background sounds also results in reduced sensitivity in the high range.

For very helpful information about the workings of the human ear go to "How stuff Works" here

Professor Roberts at Bristol University has been investigating the auditory systems of insects at the nanoscale level. His colleague DR Windmill ..."The moth’s ears typically have only two mechanoreceptor cells, making them some of the simplest ears known to exist. However, many moths can hear large frequency ranges, from 20 kHz to over 80 kHz, in order to listen out for the echolocation calls of their predator, the bat."

Apparently these simple ears operate with incredible precision ..."Dr Windmill’s investigations have shown that the faintest sounds that moths can hear cause motions of the tympanal membrane of about 50 picometres (one picometre is a thousandth of a nanometre, which is a billionth of a metre). This extreme sensitivity is the equivalent of the Clifton Suspension Bridge moving up and down a fraction of a millimetre."

In work at Cornell University ..."Ormia flies, can detect changes in sound-source position as small as 2 degrees. Even humans trying to detect who is speaking in a crowded room can't do better than that.

The need for such precise location is due to the need for the female Ormia fly to detect and locate singing male crickets -- where they climb aboard and deposit tiny larvae that develop into larger maggots which feast on the crickets, from the inside out.(Ugh!)

Crickets have been observed in the field and can hear bat echo location signals and move faster than the response time for the bat to locate them.

Microbats, which exist in the UK use echo-location to locate their prey - mainly insects. (Pic Brown Long Eared Bat) Megabats like the Flying Foxes of the Tropics and Australia do not use echo location. The UK pipistrelle bat uses a range of 54-90 KHz for echo location of prey but the toal range varies from 9KhZ to 1ooKHz. In the UK bats are a protected species and it is against the law to disturb them.

The Wildlife and Countryside Act 1981 (WCA) protects bats and their roosts in England, Scotland and Wales. Some parts have been amended by the Countryside and Rights of Way Act 2000 (CRoW) which applies only in England and Wales, and by the Nature Conservation (Scotland) Act 2004 which applies in Scotland.

The Conservation (Natural Habitats, &c.) Regulations 1994 (better known as the Habitats Regulations) implements the Council Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora - better known as the Habitats Directive. All bats are listed as 'European protected species of animals'.

It is an offence for any person to:

Intentionally or recklessly disturb a bat while it is occupying a structure or place that it uses for shelter or protection.

The potential fine for each offence is £5,000. If more than one bat is involved, the fine is £5,000 per bat. An offender can also be imprisoned for six months. On conviction the forfeiture of any bat or other thing by the court is mandatory, and items used to commit the offence (for example vehicles) may be forfeited.

The average frequency of the songs of songbirds is about 4,000 Hz, approximately the same pitch as the highest note of a piano. Many warblers, sparrows, waxwings, kinglets, and a number of other birds produce sounds that reach 8,000 Hz and beyond.

Ultrasonic "silent" bird scarers are available which generate sounds in the range 15 KhZ - 30 KHz for protecting crops, preventing bird strikes at airports or flocks of pigeons , starlings in towns. details of commercial units are here, here and here.

Ultrasonic generators are available to act as mosquito repellants and underground (at 300KHz) for moles and rodents. There is no scientific evidence these have any effect whatever - except the profits generated by the manufacturers.

Portable units are very widely available also available for dog trainers / deterrant / alarms for joggers , postmen that operate at 20KHz - 45 KHz range. At high decibel levels (in excess of 85Db) this is painful to dogs and is used to deter attacking dogs and also to provide an invisible perimeter to limit dog movement.

Interestingly in the UK there are laws in place over causing a nuisance by noise ..

Environmental Protection Act 1990 (c. 43)

79.—(1) Subject to subsections (2) to (6) below, the following matters constitute "statutory nuisances" for the purposes of this Part, that is to say—
premises ....kept in such a place or manner as to be prejudicial to health or a nuisance; ...

(g) noise emitted from premises so as to be prejudicial to health or a nuisance;

...and it shall be the duty of every local authority to cause its area to be inspected from time to time to detect any statutory nuisances which ought to be dealt with under section 80 below and, where a complaint of a statutory nuisance is made to it by a person living within its area, to take such steps as are reasonably practicable to investigate the complaint.

80.—(1) Where a local authority is satisfied that a statutory nuisance exists, or is likely to occur or recur, in the area of the authority, the local authority shall serve a notice ("an abatement notice") imposing all or any of the following requirements—

(a) requiring the abatement of the nuisance or prohibiting or restricting its occurrence or recurrence;
(b) requiring the execution of such works, and the taking of such other steps, as may be necessary for any of those purposes,

and the notice shall specify the time or times within which the requirements of the notice are to be complied with.

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Presumably this was brought to the attention of the Councillors when this was introduced to prior to installation of this device and when a full risk asessment was undertaken by Council / POlice officers.... but I wouldn't bet on it.