Long term and frequent exposure to loud noise can permanently damage a person’s hearing, possibly resulting in deafness. Acute short term hearing loss can result from exposure to an instantaneous loud noise eg. an explosion, this may also have a long term affect.
Noise Sources
The first step in preventing hearing loss is to recognise if the noise is excessive. The main sources of high noise are industrial machinery, loud music and power tools. A high noise level is defined as anything above 85 decibels. A normal office noise level is around 50 decibels whereas an angle grinder cutting steel plate registers at about 108 decibels. The damage from noise exposure is called the logarithmic effect ie. with every extra 3db above 90 you can loose or damage your hearing twice as fast. Typical noise exposure damage occurs at the following rates:
- 90 decibels – after eight hours exposure.
- 93 decibels – after four hours exposure.
- 96 decibels – after 2 hours exposure.
Recognising Noise Exposure
You must be able to recognise excessive noise if you are to protect yourself against it. Besides being loud and startling, excessive noise will cause ringing in the ears, and/or pain in the ears.
A good rule of thumb to remember is that if you are speaking to, or listening to, another person who is less than one metre from you and you can’t hear or be heard – the noise is excessive.
Types of Hearing Protection
The major types of hearing protection are ear plugs and ear muffs. The two main types of ear plugs are the disposable ear plugs and canal caps. Ear plugs and canal caps pro-tect your hearing by reducing the amount of noise entering your ear canal.
Ear plugs are made of compressible foam that you roll between your fingers and then insert into your ear canal. The foam expands and creates an air tight seal, which reduces the level of noise entering your ear canal and eardrum. Ear plugs are usually a single-use type of hearing protection. Continual handling can cause ear plugs to become dirty which can lead to infections of the ear canal.
Canal caps protect your hearing in the same way as ear plugs. The only difference is that canal caps are small foam plugs attached to a flexible neckband. The neckband is placed over your head and the tip of the plug is inserted into your ear canal. They are re-useable, follow the manufacturer’s guidelines for maintenance and hygiene.
Ear muffs protect your hearing by creating a complete noise barrier around your ear. They consist of two hard, moulded plastic cups that are padded inside with a noise absorption material. Foam seals on the cups mould to the shape of the area around your ear to provide a seal. The cups are attached to a tensioned head or neck band that pushes the cups against the area around your ear to create the seal. When correctly fitted the ear muffs (dependent on the specification of noise reduction) provide much better hearing protection than ear plugs and canal caps.
Selecting Suitable Hearing Protection
The first step in protecting your hearing is to select the correct type of hearing protection. The first factor you must consider is how much protection you need. There is no point in wearing hearing protection if the amount of noise you’re being exposed to exceeds the hearing protection capacity for the noise reduction or noise reduction rating.
For example, if the area you are working in has a noise level of 110 decibels and your ear plugs only have a noise reduction rating of 20 decibels, you are still being exposed to high noise levels.
If you are required to wear a hard hat – ear plugs or ear muffs with helmet attachments or neckbands are the only suitable hearing protection.
In hot and or humid conditions ear muffs can be fitted with disposable absorbent tissue inserts for comfort.
Fitting Hearing Protectors
When fitting ear muffs you must make sure:
- They are placed fully over your ears;
- They are completely sealed around your ears; and
- They are adequately tensioned at the headband so they do not slip or move while you are wearing them.
Fitting ear plugs:
Roll the earplug up into a small, thin “snake” with your fingers. You can use one or both hands.
Pull the top of your ear up and back with your opposite hand to straighten out your ear canal. The rolled-up earplug should slide right in.
Faulty or Damaged Hearing Protection
Hearing protection must be in good working order to be effective. Before wearing this equipment, you must check for any faults or damage. Earmuffs and canal caps should be checked for:
- Cracks in the ear muff casings;
- Tears or deterioration in the seal or foam of ear muffs;
- Bent or broken parts protruding from the ear muffs;
- Stretched headband or neckband, which will reduce the clamp force; and
- Deterioration of foam canal caps, in which case new ones should be used.