Our volume test

We checked the volume of 6 MP3 players to see how high the volume could go. Our test was carried out at the Acoustics Research Centre of the University of Auckland.

All the models exceeded 100 decibels at full volume and several exceeded 120 decibels. That's louder than the 95-decibel limit imposed on noisy car exhausts. And it's well over the limit of 80 decibels recommended by audiologists. Even at 50 percent volume only one MP3 player was less than 80 decibels.

University of Auckland Professor of Audiology Peter Thorne said the levels recorded in our test were potentially dangerous. "People shouldn't be exposing themselves to those sorts of levels". He likened 120 decibels to the noise of a taxiing jet airplane. "Once you get over 115 decibels you are in the 'red zone' and your hearing can be permanently damaged with brief exposure," he said.

Professor Thorne would like to see manufacturers taking more responsibility for informing consumers about the dangers of playing MP3 players too loud. He's also in favour of a public-education programme warning about the dangers of hearing loss from loud music.

How loud is too loud?

Noise is measured in units called decibels, on a scale of zero to 140. The higher the number of decibels, the louder the noise - and the greater the risk of hearing loss. Hearing loss can occur with regular exposure to noise levels of 110 decibels or more for periods longer than one minute.

No more than 15 minutes of unprotected exposure to 100 decibels is recommended. Every 3 decibel increase doubles the actual volume.

Common noises and their decibel levels.

• Firecracker (140)
• Plane taking off (140)
• Gunshot (120)
• Chainsaw (100)
• Lawnmower (90)
• City traffic (80)
• Normal conversation (60)
• Fridge humming (40)
• Whisper (20)