MP3 players should carry warnings that users risk damage to their hearing by having the volume too high, a deafness charity says.
RNID advisors tested MP3 volumes at London's Victoria station
A Royal National Institute for Deaf People poll of 10s of MP3 users at one London station found eight out of 10 had machines at more than 80 decibels.
The charity says young people should be warned that they are risking premature hearing damage.
It said there had been some interest in the idea from industry.
TIPS FOR MP3 PLAYER USERS
Even a small decrease in volume could lessen the damage to ears
Take a five minute break every hour to allow ears to recover
Over 6.3m MP3 players were sold in 2005 in the UK.
The RNID says it is not trying to stop people from listening to MP3 players - or from going to pubs, bars and clubs and enjoying music - but does want to encourage people to protect themselves against the cumulative effects of loud music.
Hearing loss from noise is caused by listening too loudly for too long a period of time.
Ringing or buzzing in the ears are "warning signs" that hearing could be damaged.
Dr John Low, chief executive of the RNID, said: "We know that young people are at risk from losing their hearing prematurely by listening to loud music for too long on MP3 players.
A quiet room at night - 20 decibels
An ordinary spoken conversation - 60 decibels
A busy street - 70 decibels
A pneumatic drill - 100 decibels
Some personal music players (at high volume) - 105 decibels
Aircraft taking off - 110 decibels
"MP3 player manufacturers have a responsibility to make their customers aware of the risks and the need to listen at sensible levels and we urge them to incorporate prominent warnings into the packaging of their products.
"New technology and ever-increasing storage capacity enable people to listen non-stop for hours - and at louder volumes than ever before.
"If you are regularly plugged in, it is only too easy to clock up noise doses that could damage your hearing forever."
He added: "It's clear that young people are not only shockingly unaware of any risk to their hearing, but also that manufacturers aren't yet doing enough to warn people.
"We want people to be aware of the risks and take control to protect their hearing and are willing to help manufacturers come up with an effective solution to this growing problem."
Angela King, a senior audiologist at the RNID, says there are ways people can protect their hearing.
"We are encouraging all users of MP3 players be aware to 'turn it down a notch' - even reducing the volume slightly can go a long way to reducing the damage to your ears."