Noise Induced Hearing Loss (NIHL) is an entirely preventable yet irreversible impairment harming a considerable number of Australian workers. Affecting approximately 4700 people each year, it amounted to $41 million in workers' compensation payments and had an estimated total economic cost of around $240 million. Around 1.1 million people in Australia live with an untreated, disabling hearing loss, with financial costs of hearing loss in 2017 estimated to be as high as $15.9 billion.
Often seen as a ‘silent’ injury, since it is not visible, NIHL results from exposure to noise, which can cause irreversible hearing damage. It is one of the most common health problems in the workplace but can be difficult to detect as the effects build up gradually over time.
Throughout all industry, industrial hearing loss remains the occupational disease with the highest number of civil claims accounting for about 75% of all occupational disease claims. One of the main reasons NIHL remains so widespread is a lack of awareness, which can largely be attributed to gaps in legislation combined with inadequate training practices.
Causes of NIHL
There are two main types of noise and two basic types of NIHL. The first type of noise is general background noise such as that found in a busy workplace, with whirring machines. The second type is impact noise, a one-time intense impulse such as an explosion.
Both types of noise overstimulate the delicate hairs in the ear, leading to permanent injury. Gradually developing NIHL is caused by the first type of noise, whereby permanent cochlea damage occurs from repeated and multiple exposure to loud and excessive sounds over a period of time.
However, single exposure to a high-intensity sound pressure level can cause acoustic trauma and potential immediate hearing loss. Sounds of less than 75 decibels are unlikely to cause hearing loss, even after long exposure, whereas sounds that are 85 dBA or above can permanently damage hearing.
Furthermore, the more sound pressure there is, the less time it takes to cause damage. For example, a sound at 85 dBA could take up to eight hours to cause permanent damage, whereas a sound at 100 dBA can start damaging hearing after only 15 minutes. Don't be fooled by how small the increase is - the decibel system uses a logarithmic scale, meaning that every 10 decibels is an increase of 10x. 100 dBa isn't 10x as loud as 10dBa - it's 1,000,000,000x (a billion times!) as loud as 10dBa.
Hearing loss can also be caused by workers not wearing adequate hearing protection, or wearing ill-fitting protection, and workers not being properly trained in this area.
There are many forms of hearing protection including earmuffs, earplugs and moulded earplugs, each providing excellent attenuation for different applications. However, if not fitted correctly, they let noise in, causing damage. For example, even though an earplug may appear to be inserted properly, there may be a hidden leak which can significantly reduce protection levels.
Improper sizing and selection, or even a crease in an earplug, may cause an acoustic leak that is not readily visible. Even when fitted properly, sometimes the wrong equipment - using earmuffs when earplugs are more applicable - may result in an inadequate level of attentuation.
The effects of NIHL
What does the worker physically feel, and what are the perceivable effects? If hearing loss develops slowly, the first symptom of NIHL may be difficulty hearing a conversation against a noisy background. The worker may also experience muffled sounds and tinnitus, and will lose audibility and experience an overall decrease in volume. Hearing will also become distorted and clarity will be lost.
Tinnitus may present itself in a number of ways – it may sound like an intermittent or continuous buzzing, humming or ringing, when there is no external cause for the sound. The sound may be heard in one or both ears, or in the head. Tinnitus is very common and is reported in all age groups, even young children. According to Better Health Victoria, approximately 17-20% of Australians suffer from some degree of tinnitus, varying from mild to severe. About 1 in 6 Australians have constant tinnitus symptoms.
For those that experience an extreme loud burst of sound, the eardrum may rupture and bones in the middle ear may be damaged. In this case, the worker will suffer an intense pain.
However, the effects are more than just physical. Hearing loss can have long-term psychological effects and a wider effect on a person’s overall health and wellbeing. It is these effects that are often overlooked. Not being able to hear properly can have a devastating negative impact on communication and this will have wider adverse effects on social interactions.
Being unable to communicate in a way that someone is used to means that person may become withdrawn, and start to feel isolated. This in turn can lead to reduced self-esteem, shame, fear, anger, stress and/or depression. Tinnitus may also be a constant presence, leading to a loss of concentration, and/or preventing someone from sleeping properly.
Costs of NIHL
Effects of NIHL are not only felt by individuals, but can have significant implications for a business. NIHL is becoming ever more prevalent, and the cost of failing to protect workers and following set procedures can hit the bottom line heavily. In 2001/2002, the direct cost of occupational noise induced hearing loss to Australia was just over $30 million.
Costs can be incurred as a result of lost productivity whilst workers are absent through illness. Workplace absenteeism costs the Australian economy more than $44 billion annually.
What should I do?
There are numerous solutions at all levels of operation that can be performed to lower the odds of workers suffering from NIHL. For a regular worker, the most important thing to do is to ensure that your PPE is correctly and consistently used properly as intended by manufacturers. If it doesn't fit, it's not PPE - it's an accessory. Earplugs shouldn't be a fashion statement.
The Norwegian offshore maintenance operator Beerenberg Group, for example, performed a fit-testing exercise on 288 of its workers in 2013, which revealed that nearly 40% of them were not using their PPE correctly. This means that they were receiving insufficient attenuation (less than 16 dB) even though the earplugs used had a noise reduction rating (NRR) between 30-34 dB.
Strikingly, when the test was repeated after one-to-one fit-testing training, the percentage of workers with a poor fit dropped to just over 5%. It is clear that training programmes incorporating fit-testing should underpin any hearing conservation effort.
However, if you're higher up the chain of command, you should try to do more than simply ensure proper PPE usage.
Employers must ensure employees’ exposure to noise does not exceed the exposure standard by attempting to implement the following hierarchy of control measures:
- eliminate the source of noise
- substitute noisy plant for quieter plant or processes or implement engineering controls
- use administrative controls
- provide hearing protection
An employer must provide hearing protectors when employee exposure to noise cannot be reasonably eliminated or reduced to below the noise exposure standard using substitution, engineering and administrative controls.
Class of hearing protector required
Under the Australian Standard AS/NZS 1270:2002, the class is an easy way to choose a hearing protector appropriate to a noise exposure. The standard rates hearing protection into five classes, with Class 1 being the lowest level of protection and Class 5 being the highest level.
The system is based on the SOUND LEVEL CONVERSION (SLC80) rating which is the difference between the sound level of the environment in which the hearing protection is worn and the sound level reaching the wearer’s ears. This is converted to a Recommended Noise Range.
Once the extent of the noise hazard has been determined by a noise level survey, the user simply applies this to the table below for selecting an appropriate hearing protector
For example, if a person is exposed to noise with a LAeq,8h of 97 dB(A) a Class 3 hearing protector is suitable.
| LAeq,8h db(A) | Class |
| Less than 90 | 1 |
| 90 to less than 95 | 2 |
| 95 to less than 100 | 3 |
| 100 to less than 105 | 4 |
| 105 to less than 110 | 5 |
| Greater than or equal to 110 | Seek specialist advice |
