What is Noise-Induced Hearing Loss
Hearing loss can be caused by getting older or inheriting a family trait of deafness; or by damaging your hearing through too much noise – either one very loud bang which damages the hearing apparatus in your ear (many soldiers get this); or if you work for long periods in a noisy place, for example, with machinery. This called Noise-Induced Hearing Loss or NIHL. Years ago it was called ‘Industrial Deafness’.
The deafness caused by working in a factory say, is easily found by having a hearing test and looking for a particular pattern of hearing loss on the audiogram picture.
Many look for the 4KHz ‘dip’ or what the Americans call ‘the notch’ on the graph and although this is an important factor, it is not, in itself the full story. Workers have notches at other kHz’s too and the ‘dip’ could be caused by genetics or even trauma to the ear.
How is Noise-Induced Hearing Loss caused?
Deep inside both ears are layers of tiny hairs that twitch as noise vibrations reach them (like ripples on water). The hairs, as they vibrate, transmit the vibration as an electrical signal to the brain via the auditory nerve. Different groups of hair cells pick up different frequencies (like speech or music).
The healthy ear can hear a large range of sound, but over time damage occurs to the tiny hairs or they break due to overuse or if the noise is excessive. When a large number of hairs are damaged, your hearing starts to go. In the workplace, high-frequency noises, say from presses and drills, damages hearing, which is why you must wear hearing protection. Hearing protection provides a barrier that stops some of the sound waves reaching into your ear and prevents damage to the delicate hairs.
Measuring Sound Levels
Sounds are measured in decibel (dB). The average person can hear quiet sounds such as rustling leaves. Some people with very good hearing can hear an even quieter sound. However, sounds over 85 dB or stronger, cause permanent damage to your hearing, that is, your hearing will never come back to normal. Time is also important because the amount of time you hear a noise affects the damage that might be caused. The quieter the sound, the less damage it will cause. If the sound is very quiet, it will not cause damage even if you listen to it for a very long time.
With extended exposure, noises that reach a decibel level of 85 can cause permanent damage to the hair cells in the inner ear, leading to hearing loss. Many common sounds are louder than you think. Both the USA and the UK agree on the recommended sound levels that are unlikely to cause problems:
In the UK the Control of Noise at Work Regulations sets out the law which employers have to follow. But, easier to understand is HSE’s, full guidance which employers can download for free here: Controlling Noise at Work.
If you work in a noisy area, hearing protection, by law, must be provided. This will be ear muffs, pads or earplugs, but remember, these only remove some of the noise; some is likely to penetrate through especially if they are worn incorrectly.
You can also keep away from noise hazards, that is, don’t walk through a noisy factory if you don’t have to. Or don’t add to your time exposure by playing loud music in your earphones although there is little evidence to show that this is such a big factor as everyone believes – read 5 myths in assessing the effects of noise on hearing. by William Clark PhD.
If you are exposed to loud noise during your work, you may have a hearing check. This way, your employer is making sure your hearing has not been affected or discover if there are some changes happening by looking at regular readings. Some people are more sensitive to harmful noise than others. If you have a problem then others are likely to have a problem too – it means the noise levels are too high or your hearing protection is not working. If you’re found to have noise-induced hearing loss then you will need a full assessment, usually by a specialist at the local hospital.
What Happens at a Hearing Test
Occupational health services undertake a hearing test on many sites, either in a booth or in a quiet room. The nurse/doctor will also:
- Ask you questions about your hearing and you will fill in a questionnaire
- Look into your ear with a small torch. They are looking to see if there is anything in your ear that may affect your hearing levels such as lots of ear wax or an infection
- Ask you to wear headphones where you will hear different sounds – you have to press a button when you hear the sound. Your responses are recorded to make a picture of your hearing (see audiogram picture above). Each ear is tested separately as the results are often different.
- Explain the result of your test to you and tell you if you have hearing loss
- Explain the importance of protecting your hearing and show you how to wear your hearing protection, for example, how to properly insert ear plugs
If you have a significant loss of hearing you may be asked to see your GP for further tests. Remember you have to protect whatever hearing you have, so, if there is hearing loss, your employer may decide to move you out of the noise hazard working area.
Noise-induced hearing loss is an industrial disease and is automatically compensated for under the Industrial Injuries Disablement Benefits scheme (A10). Click on the link to find out how or check with your trade union or worker representative.