Why the concern?

Here's why we should be worried. Some MP3 players have the capacity to exceed 100 decibels, well over the 80 decibels at which hearing is threatened. The higher the volume, the greater the threat to your hearing. A safe listening level is surprisingly low - about 60 decibels (the same as conversation speech). It's at this level that audiologists say it's safe to listen as long as you like.

However, Wellington Hospital's head of audiology services, Sargunam Sivaraj, says the variations in the volume levels of MP3 players make it difficult to recommend universal guidelines for how long you can listen. It will depend on the maximum sound output of your MP3 player.

The problem is hearing damage takes years to show up. Unlike a blast from a firecracker, the consequences of listening to loud music are more subtle. Hearing clinics are treating people who began working on industrial sites when they were in their teens. Now aged in their 30s and 40s, these people are starting to notice the effects of hearing loss.

While there's anecdotal evidence of young people suffering serious hearing loss from their MP3 players, audiologists say it's too early to see the full effects of hearing damage from this source. But they warn it's only a matter of time.

In New Zealand it's estimated 10 percent or 400,000 people report some form of hearing loss. This number is expected to grow as the population ages. Studies in Australia have shown 17 percent of adults have some form of hearing disability, and some experts here say our rate is likely to be similar or even higher. This is because of the higher rate of hearing loss among Maori, compared with non-Maori.

Then there's the economic cost. A 2006 study by Australian economic consultants Access Economics estimated the "real" financial cost of hearing loss to the Australian economy at $11.75 billion (or 1.4 percent of GDP).

The risk with MP3 players is that people are exposing themselves to another potential source of hearing loss when they already have to cope with workplace noise and other types of damaging noise.

Researchers are agreed: your ears need a rest from sounds in the higher decibel levels if you want to avoid irreversible hearing loss.