MUSIC fans have been warned to turn down or switch off their iPods amid fears the craze for MP3 players is storing up catastrophic and irreversible hearing damage for a generation.
The iPod - like all digital music players - is compact, stores huge amounts of music and can play for many hours. As a result, more people are listening for longer to their favourite tracks.
But audiologists believe tens of thousands of young people are causing serious damage to themselves, and are likely to suffer tinnitus and loss of hearing in later life. The experts say MP3 players should be designed to prevent people playing music above 90 decibels, about two-thirds of the maximum volume of a typical device.
Perhaps more worryingly for people who have 3,000 songs stored on an iPod, they also say listening should be restricted to no more than an hour a day.
The original Walkman played cassettes with a maximum duration of two hours, while portable CD players give up to 80 minutes a disc. A typical MP3 player, however, can store up to 300 hours of music and has batteries that last for 12 hours before needing to be recharged.
Volume controls on many of the machines can be cranked up to in excess of 100 decibels, equivalent to standing five metres from a pneumatic drill.
"It would obviously be beneficial to reduce the volume and restrict the usage of personal players," said Christine DePlacido, principal audiological scientist at the Victoria Hospital, Kirkcaldy. "The difficulty is in persuading people to do this before their hearing is damaged, as many believe hearing loss will not happen to them until they are much older.
DePlacido added: "A lot of the young people I see with tinnitus describe listening to music at high intensities. It would be hard to say how great this problem is, bearing in mind I only see people who are distressed by their tinnitus. I imagine there are a lot more people out there who are just living with it."
Tinnitus and noise-induced hearing loss occurs when the delicate hair nerve cells that line the inner ear undergo repeated trauma from loud sound vibrations.
The Royal National Institute for the Deaf (RNID) is so concerned about the damage being caused by MP3 players, it has issued advice on how to use them safely. Lisa McDonald, RNID campaigns officer, said: "Most people are listening to their iPods on public transport to drown out the noise of traffic, but to do this they turn them up to quite dangerous levels.
"For example the noise on the London tube is about 90 decibels which is already loud enough to cause damage with a long period of exposure.
"Because music is enjoyable people are much more willing to tolerate those levels of noise for much longer."
Research by London-based audio expert Tony Hale has revealed that general noise levels have soared threefold compared with 30 years ago.
He found the average street was 330% noisier than the countryside, with noise in busy city centres reaching 90 decibels.
Experts say people are having to turn up their MP3 players higher than was needed in the days of the Walkman in order to block out this clamour.
Dr John Irwin, an audiology surgeon at Ninewells Hospital, Dundee, said: "The potential for damage exists because of the maximum output available from these devices. The process is a slow one rather than sudden, except in very unusual circumstances."
A survey by RNID in 2002 found just 46% of young people in Scotland knew loud music could irreversibly damage their ears. It estimates about 340,000 teenagers may be at risk of hearing damage due to listening to amplified music.
Research shows 39% of 18 to 24-year-olds listen to personal stereos for more than an hour each day, with 13% listening for two hours or more.
Many MP3 players in Europe have now had volume levels capped at 100dB after authorities in France ordered a clampdown on the devices.
No one from Apple, who make iPods, was available for comment.
MOVING WITH THE TIMES
THE history of personal stereo systems dates back to the 1960s with the boom in portable AM band receivers. These battery-powered systems were sold by companies such as Panasonic, Toshiba and Olympus. But the invention of the Sony Walkman was an accident.
Changes at Sony in 1979 meant that the tape recorder division was pressed into inventing a new product or risk facing consolidation. They came up with a small cassette player capable of stereo playback.
The first models were marketed in the US as Sound-About and in the UK as the Stowaway.
The product proved popular in Japan and hit the US in 1980. By the spring of 1981, at least two dozen companies were selling similar devices and by 1983 everyone wanted a one. Three years later the word Walkman entered the Oxford English Dictionary.
The end for Walkman came in 1986 when Sony announced the D-50, a portable audio device that could play the "perfect" sound compact discs. They called it the Discman.
Then in November 2001 Apple blew the competition out of the water with its new digital invention, the iPod. No larger than a cassette box, it could hold up to 10,000 songs.