Updated: 15 Mar 2010

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Introduction

Can MP3 players damage your hearing? It's an issue that has audiologists worried.

A growing numbers of people are plugging into their digital music players, pounding their ears with loud music, and putting their hearing at risk. We take a look at whether this is likely to cause future hearing loss, and give advice on how to limit the damage.

We regularly test MP3 players and have found that, when set to maximum volume, most models exceed the safe level recommended by audiologists.

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.

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)

Headphones versus earbuds

Most MP3 players have headphones that sit directly in the ear (earbuds). There's debate about whether these are more harmful than the older-style headphones which sit over the ear.

But, Boston Children's Hospital audiologist Brian Fligor says the types of headphones are important: "The closer to the eardrum, the higher the sound levels the system is capable of producing," he told Rolling Stone magazine.

Fligor found that on average a person can listen to over-the-ear headphones with a player set at level six (out of ten) for an hour a day. For most earbuds the acceptable limit was half that for some models - 30 minutes a day at the same level.

Sydney's National Acoustic Laboratories research engineer Warwick Williams agrees earbuds could be more dangerous because they sit directly in the ear, and so there's the potential for greater penetration of noise directly into the ear. But he points out earbuds also have the potential to be less damaging - you might keep the volume lower because earbuds are more effective at blocking out the sound around you.

Auckland University audiologist Dr Grant Searchfield says the new technology throws into doubt an old rule of thumb. "We used to say if you were an arms length away from a person and you could hear the sound coming from the earphones - that was potentially damaging. Many MP3 player earphones are now sealed in the ear, so sound is less likely to leak out and be heard by someone else. Because of this parents may be completely unaware of how loud their children's music is."

Causes of deafness

All noise damages the hearing system in a similar manner. The ear is made up of three parts: the outer ear (pinna or auricle); the middle ear, which includes the eardrum (tympanic membrane); and the inner ear (cochlea) which is shaped like a snail shell and lined with tiny hairs.

Hearing loss occurs when the hairs inside the cochlea are damaged or die, which is a common occurrence as people age. Hair cells, which pick up sound waves and transform them into nerve impulses that are passed to the brain, do not regenerate. That's why most hearing loss is irreversible.

Symptoms of deafness

Many people don't realise they're going deaf. Our own built-in defences and ability to adapt makes it difficult to self-diagnose.

First you begin to lose the subtleties of language and find it hard to hear in situations where there is background noise. Then you find it hard to hear the television or while you're talking on the phone and with further hearing loss you have difficulty hearing one-to-one conversations.

You might be damaging or over-exposing your ears if you notice any of the following symptoms after listening to extreme sound on your MP3 player, Walkman or Discman:

• Voices suddenly sound muffled and are hard to understand.
• You experience ringing, buzzing or fluttering in one or both ears (this is known as tinnitus).
• Your ears hurt after being in a loud place.
• Your ears are suddenly super sensitive to noise.

If so, stop using the player and have your ears checked by a registered audiologist.

You can't get it back again

There's a widely held perception that hearing aids will compensate for hearing loss as effectively as glasses correct optical problems. They won't. Your ears have been permanently damaged and because the "connection" has been broken it's impossible to restore clear hearing. With a hearing aid you can expect the noise to be louder, but still muddy.

"That's why they are called assisted listening devices - because they don't bring it back to normal again," Research Engineer Warwick Williams says.

Williams would like to see a public education programme on the dangers of noise exposure similar to those used to highlight the dangers of sunburn, smoking, drugs and sexual habits.

Audiologists we spoke to opposed limiting an MP3 player's decibel output - as happens in Europe where they are capped at 100 decibels by law. Most preferred an effective education programme. In New Zealand two companies - Apple and Sony - have introduced devices to limit their players' decibel output. But it's up to the consumer to take the initiative.

Experts warn that, unless prevention of hearing loss becomes a health priority, a considerable portion of health funding will have to be spent on hearing loss rehabilitation.

Government assistance

There is a universal hearing aid subsidy for adults who aren't eligible for funding from ACC, Environmental Support Services or the War Pensions Scheme. This part-subsidy of $500 per hearing aid ($1000 for the pair) is available every five years to people with hearing loss.

That's a paltry sum if you consider hearing aids range from $1200 up to $7000 a pair. The subsidy doesn't cover the cost of batteries, and there is no increase in the subsidy if better technology is recommended by your audiologist.

Our advice

Listening to your MP3 player

Always follow the 60/60 rule. Audiologists recommend safe exposure as being 60 minutes a day with the volume no higher than 60 percent. If you listen for more than 60 minutes, you should turn the volume down below 60 percent.

Set the volume when you are in a quiet environment and don't turn up the volume to block out noisy surroundings.

Follow this simple rule of thumb: if you can't hear other people talking when you're wearing headphones, or if other people have to shout at you to be heard a metre away, it's too loud and could be damaging your hearing.

Getting a hearing aid

The key to getting the best hearing aid is the person who fits it. Always have a hearing aid fitted by a registered audiologist. The NZ Audiological Society provides a full list of members on its website. If you're concerned about who to see, get recommendations from your doctor, local hearing association, a hearing therapist, or friends.

Don't expect too much, particularly at first. It will take time and perseverance to get used to wearing hearing aids to get the maximum benefit from them.