Noise induced hearing loss

Information on noise induced hearing loss: what it is, how to prevent and manage it and studies and research into the subject.

Imagine, you’re a retired builder. During 45 years in the trade you’ve hammered in thousands of nails and cut many four by twos with a circular saw. You wore earmuffs for the last ten years or so but you didn’t worry if you left them at home the odd day.

Now you’re having your monthly lunch with old friends. You listen hard but it’s like you’re underwater - their words are muffled and you can’t understand what they’re saying. There’s a loud hissing and ringing in your ears that kept you awake most of last night, and that doesn’t make things any easier.

You get tired of asking people to repeat themselves so you just sit and eat. You’d like to catch up on everybody’s news, but find yourself thinking that you probably won’t come next time.

It’s quite likely that noise induced hearing loss is the reason why.

What is noise induced hearing loss (NIHL)?

Noise induced hearing loss is permanent deafness that happens when your ears are exposed to sounds over a period of time which are generally too loud for them to handle. It doesn’t hurt and it doesn’t happen straight away, so you don’t know it’s happening. In fact it can take ten or twenty years before you know you’ve got a problem, and by then there’s nothing you can do except prevent further damage.

NIHL deafness usually affects both your ears and makes it hard to understand speech, especially if you’re talking with a group of friends or family. When conversation is hard you can end up keeping to yourself, and that can leave you feeling lonely and depressed.

You can also get tinnitus. This is uncontrollable ringing or other sound in your ears, which your brain creates to make up for sounds you don’t hear any more. The sound can be annoying and distracting, and if it’s loud enough you can find it very hard to sleep.

How big is the problem?

In 2011 ACC commissioned research (PDF 418K) to capture the latest information about preventing NIHL in New Zealand. The research report estimated that approximately 445,000 New Zealanders (10% of the population) live with hearing loss (taken from the Statistics New Zealand website (external site), and about a quarter of them are affected by NIHL. Here are some more facts:

  • approximately 71,000 (16%) have deafness that is due to NIHL, and
  • approximately 40,000 (9%) live with NIHL on top of other hearing loss, and
  • 95 percent of the people who have NIHL are male.

On average ACC receives 8 claims for NIHL each day, which add up to more than $10 million each year. This cost impacts on the levies paid by industry. Those who live with NIHL also pay a high price in social isolation, and sometimes their deafness means they lose their job.

Where is NIHL most likely to happen?

The highest average workplace noise levels are found in agriculture, mining, construction and manufacturing. And many activities outside the workplace can be just as noisy, such as:

  • ‘do-it-yourself’ construction and maintenance projects at home, like lawn mowing, using power tools and chain saws
  • loud music at night clubs, bars, live music events or fitness classes
  • listening to music on your iPod, home stereo, car stereo
  • when you’re working or playing around a noisy engine, i.e. riding a motorbike, motor racing, waterskiing etc.
  • when you’re hunting or target shooting.

How noisy is too noisy?

Try ‘the conversation test’ first. Here’s the test - if you can’t have a conversation without raising your voice to be heard, then the noise where you are is too loud. You’re damaging your hearing just by being there.

If you’re not sure whether your workplace is too noisy, or some of the sounds in your workplace are too loud, it’s a good idea to get a professional noise assessment (external website) done. If there are problems then you can do something about them, and this will help you to meet your legal requirement to protect your employees from excessive noise.

What are the legal requirements?

The Health and Safety in Employment Act 1992 (external website), the Health and Safety in Employment Regulations 1995 (external website) and the Approved Code of Practice for the Management of Noise in the Workplace (external website) say that employers must take all practicable steps to ensure that no employee is exposed to noise above (a) eight continuous hours of 85 dBA, and (b) peak sound of 140 dB, whether or not the employee is wearing HPE.

Top NIHL prevention priorities for employees

  1. If you have hearing protection equipment (HPE), wear it. Never wear your HPE over any kind of beanie or hat because that stops it from working! You need to wear it in all noisy work areas and whenever you’re doing noisy tasks.

    Remember, even a short exposure to very loud noise (such as firing a gun) hurts your hearing, never mind being in a noisy place all day. As a rule of thumb, if you have to raise your voice to be heard, you need to protect your hearing.
  2. If you don’t know how to use your HPE properly, ask for training. It might take five minutes, but it will help to protect your hearing for life.
  3. If your HPE is worn, doesn’t fit or is uncomfortable to wear, talk to your supervisor about getting something that works for you.
  4. NIHL is not part of your job! If your workplace is noisy, talk to your supervisor about it.

By law your employer must provide you with a healthy and safe workplace, and that includes helping you to take care of your hearing.

Top NIHL prevention priorities for employers

1. Reduction of noise at source

The best way to prevent NIHL is to reduce the amount of noise that is produced by equipment or machinery in the first place. There’s an up front cost when you buy quieter equipment but once it’s done it’s done, and it generally pays you back in the long run. If this isn’t an option, see if you can:

  • substitute a quieter tool, machine or process for a noisy one
  • find ways that your employees can do their work more quietly, and if there are, train them to work that way
  • get engineering assistance to reduce noise to acceptable levels.

Some engineering solutions can be expensive, but many are low cost and simple to do. For example, a major source of noise in milking sheds is the motor that drives the milking machine. Researchers found that all they had to do was mount the motor on a concrete block, and the problem went away.

2. Be a champion for hearing protection in your workplace

There will probably be some noises you can’t quieten down, either in the short term or the long term. This means your employees still need to protect their hearing, even though it’s sometimes challenging to make this happen. You need to:

  • explain that while they may not feel any pain or have problems hearing now, by the time they notice NIHL it will be too late to do anything about it
  • work together with your employees and supervisors to identify sources of noise, agree on how you’re going to manage the noise (get a professional assessment and advice if you need it) and who will do what
  • make sure everyone does what you’ve agreed to do about managing the noise
  • lead by example - wear your own HPE consistently to show everyone that you’re walking the talk and you expect them to do the same.

3. Use hearing protection equipment (HPE) effectively

It’s harder to use hearing protection equipment (HPE) effectively than you think. Doing it properly means you need to:

  1. Have each employee’s hearing checked annually. This is usually done by an occupational health nurse or an audiologist.
  2. Provide the right kind of HPE. You can consult the Approved Code of Practice for the Management of Noise in the Workplace (external website) for help to choose the right gear for each job or environment, or you can get professional assistance (external website) with this.
  3. Keep HPE well maintained and fit for the job it has to do.
  4. Make sure that employees wear HPE correctly. For example many employees wear ear muffs over a woollen ‘beanie’ hat in cold weather. The problem is that the hat stops the ear muffs from sealing properly around the wearer’s ears. Without the seal, the muffs provide almost no protection from noise at all. However the employee thinks he’s protected and carries on doing noisy tasks.
  5. Make sure that your employees wear their HPE all of the time they are exposed to noise, because even a short break in protection does almost as much damage as being exposed to the noise all day.
  6. Replace worn or damaged HPE promptly.

Unfortunately even effective use of HPE doesn’t guarantee protection from NIHL for everyone. This is because some people’s ears are more sensitive than others. However effective use of HPE does greatly reduce the risk that your employees will get NIHL.

When you see it like this, reducing noise at source is much simpler!

4. Work with employees to make sure HPE is worn

It can sometimes be a challenge to get employees to wear HPE consistently, even when you provide the right gear and teach them how to use it. For example the research ACC commissioned in 2011 found that only 33 percent of New Zealand production workers in noisy environments wore HPE.

Reasons why employees don’t wear HPE include:

  • discomfort – see if employees can try HPE before you buy and remember that one size or brand will not fit all
  • not understanding that HPE is necessary even though their ears don’t hurt and they can still hear everything fine – make sure employees understand that NIHL can take 10 to 20 years to happen, but once it’s done there’s no fixing it
  • having difficulty hearing instructions, alarms or warnings – think carefully about how to do work safely when employees are wearing HPE, you may need to change the way you do some jobs.

If your employees aren’t wearing their HPE, ask them what the problem is. Work with them to find ways to solve the problems.

5. Get the Dangerous Decibels programme going in your workplace

The Dangerous Decibels programme will teach your employees how to protect their hearing in a simple, enjoyable and effective way. Here’s how it works.


You release one or two of your team to go to a free two-day Dangerous Decibels educator training course, run by the University of Auckland Audiology School and ACC. They’ll learn:

  • basic anatomy and physiology of the ear
  • how sound is created and how hearing works
  • how NIHL can affect their hearing
  • ways to protect their hearing: turn the noise source down or off, move away from it, or use hearing protection.

When they come back, your new Dangerous Decibels educators share what they’ve learned by presenting the interactive 45 minute Dangerous Decibels programme to the rest of the team.

This investment of your employee’s time means your whole team can learn how to protect their hearing in-house, with minimal fuss, and then they can also take the knowledge home to their families. Your trained educators can also present the Dangerous Decibels programme to community groups.

For more information about enrolling in the Dangerous Decibels educator course please email

About the Dangerous Decibels programme

The Dangerous Decibels programme was developed at Oregon Health and Science University. It has been adapted for New Zealand’s schools (as the Listen Up programme) and workplaces and is now taught by the audiology department of Auckland University.


Some of the following resources can be ordered. To find the resources to order, go to our Publications page.

ACC research on noise induced hearing loss

Updated: 14 January 2016

Reviewed: 23 January 2014