Hearing damage is preventable
Volume 11, No. 44, June 01, 2006
By Maj James Roche

Plug it: Protection can be essential in certain situations, making the right selection is a must.

NOISE induced hearing loss is irreversible, but it is a preventable injury. Excessive noise is a significant health risk and causes one of the most common occupational injuries.

Exposure to excessive noise can occur through repeated or continuous exposure or through single exposure to very loud noise levels. Either of these will often result in temporary hearing loss.

Noise is the brain’s interpretation of variations in pressure caused by vibrations in a medium such as air or water. It is measured in decibels (dBs) and is most often displayed as either dB(A) or dB(C). dB(A) refers to sound pressure levels for steady or continuous noise sources, while dB(C) is used to reflect the peak sound pressure level of impulse noise such as rifle fire or other short, sharp noises.

Decibels are measured on a logarithmic scale and therefore it is important to realise that doubling the sound pressure level does not double the number of dBs. Actually a doubling in sound pressure levels results in only a six dB increase, while a ten-fold increase in sound pressure results in a 10 dB increase.

Noting that the threshold of pain is approximately 130 dB, the following are examples of different noise levels: 84mm Carl Gustav = 180dB(C), jet engine (at 25m) = 140 dB(A), tank engine = 110 dB(A) and normal conversation = 60 dB(A). The legislated sound pressure levels, above which protection must be used, are 85 dB(A) as an average exposure over an eight-hour day and 140 dB(C) for impulse noise.

Although we recover from a temporary shift in our hearing, we rarely recover to the same hearing capacity we had before being exposed to loud noise. Therefore, it is essential that suitable control measures be applied to reduce the exposure to the noise hazard. Although the use of hearing protection is the most common, protective equipment should only be used after attempts have been made to reduce the amount of noise reaching the ear.

In a static environment such as a workshop, noise may be reduced through substituting equipment, better maintenance of machinery, or through engineered solutions such as sound barriers, reduction in reverberation, or the use of noise insulation or dampening material. If these measures do not reduce the noise sufficiently, hearing protection is required. This can take a number of forms such as earplugs, ear muffs or combinations of both.

Where occupational hazards exist, the surrounding area should also have appropriate signage to alert people to the hazard and to advise the requirement for hearing protection. Additionally, soldiers should be trained in the need for hearing protection, selection of the most appropriate type and the most effective method of care and maintenance. In the field, a good set of reusable plugs in a dust-proof case should be part of your kit, as long as they are regularly cleaned.

If not fitted correctly, ear plugs offer little protection. It is essential that they be inserted into the outer ear canal as far as practicable while still allowing their removal after use. Remember, disposable plugs are exactly that. Use them once and discard them, otherwise you run the risk of developing ear infections.

For further information see Safetyman, Volume Two, Chapter 19.