A quiet word about hearing protection
August 1st 2008

The ear is a very delicate part of the body and the damage that noise can cause is often nonrecoverable.

However, as hearing loss is cumulative and gradual over a period of years, many individuals will not realise that their hearing is being affected explains Jacqui Gamage To address the problem of work-related hearing loss, the European Physical Agents (Noise) Directive 2003/10/EC came into force in 2006. In simple terms, the Directive requires that excessive noise has to be eliminated, and that if this is not possible hearing protection should be available at 80dB, and must be worn at 85dB.

First, reduce noise levels Taking steps to reduce the noise level is always the first priority and the use of hearing protection the last resort.

Sometimes there is no option, and specifiers will need to look at the amount of sound attenuation required, wearer comfort, product certification and also compatibility with items such as other personal protection equipment, spectacles, jewellry and so on.

There are essentially three types of hearing protection: ear muffs, ear plugs and helmet mounted ear defenders. Ear-Muffs consist of two ear cups filled with sound absorbing foam and the cushioned cups are held in place over the ears by a tensioning headband. Ear-Plugs are inserted into the ear canal, and there is a wide variety of styles and materials available. Ear defenders are specifically designed to be mounted on industrial safety helmets. They are adjustable, so they can be positioned over the ear when required, or 'parked' away from the ear at other times.

Too much protection? Performance of all hearing protection is assessed by attenuation testing, which requires a tester to sit in an anechoic chamber and be exposed to various frequencies and decibel levels of noise. Unlike most forms of PPE, it is possible to have too much hearing protection because the wearer needs to be able to hear warning sirens and approaching vehicles; the inability to communicate or hear anything can also be disorientating. The level of a product's noise attenuation is indicated on the product or packaging by the Simplified Noise level Reduction or Single Number Rating (SNR). It is the figure subtracted from the overall sound measurement to calculate the sound pressure level at the ear when wearing this particular ear-defender.

If you have done an assessment and know your noise exposure, you should know the level at different frequencies. The noise energy level should be measured at 63HZ, 125HZ, 250HZ, 500HZ, 1000HZ, 2000HZ, 4000HZ, and 8000HZ, and armed with this information and the attenuation chart you can select the correct ear defender to bring the noise energy to below 80dB(A) at all these frequencies.

Know your limits The 2006 Noise at Work Regulations set the lowest action level at 80dB (A) and the second action level at 85dB(A).

If the assessment establishes that there is a problem and noise levels are likely to be at the Upper Exposure Action Values, personal hearing protection should be used immediately while other more permanent solutions are put in place.

Below the daily noise exposure rates of 80dB(A) hearing protection does not have to be worn. Between 80dB(A) and 85dB(A) hearing protection should be made available to employees who ask for them but it is not compulsory to wear them. With a daily noise exposure rate of over 85dB(A) employees must wear the hearing protection provided and the area be declared a Noise Hazard Zone with the appropriate signage. Employers will need to provide training in their correct use, until such time as noise at source can be reduced to an acceptable level.

Testing times JSP ear defenders are made in batches, and samples of each batch tested. The first test involves measuring the headband force and the area of contact to ensure that not too much pressure is applied to the wearer's head. Then an Insertion Loss test is carried out which measures sound levels at various frequencies with and without the ear defender.

Similar to attenuation figures, these figures are slightly different because electronic methods of measuring sound are used rather than the human ear.

The ear defenders are then dropped and placed on a steel vibrator plate for three hours to ensure that all components are securely attached. Then the headbands are flexed 1000 times and the headband is placed in a water bath at +50°c for 24 hours. The insertion and headband force tests are performed again to ensure that after all the physical tests the performance remains within limits.

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