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Some sound advice

23 January 2013

Christine Ohren-Bird from SATRA outlines the legislation surrounding noise exposure and offers some advice on selecting the most suitable hearing protection...

Exposure to high levels of noise can
permanently damage an

Christine Ohren-Bird from SATRA outlines the legislation surrounding noise exposure and offers some advice on selecting the most suitable hearing protection

Exposure to high levels of noise can permanently damage an individual's hearing, and even a slight degree of deafness can lead to significant loss in quality of life. In several countries, businesses have had to pay compensation for noise-induced hearing loss resulting from workplace exposure.

In industries including: construction, textile processing, engineering and the automotive industry workers will be exposed to very high levels of noise. Noise exposure should be reduced to a minimum wherever possible but in the instances where it is not possible to reduce noise exposure at source adequate personal protection should be provided. Noise exposure level calculations are commonly expressed as a 'time weighted average' over an eight-hour day, which takes into account scenarios where an operative spends a varied time working the machinery.

Within Europe there are mandatory noise exposure level requirements which have been in force since 2006 arising from the implementation of The Noise at Work Directive (2003/10/EC). This directive identifies two noise action levels. The first (lower) action level, at which workers need to be informed of the risks, given training and have hearing protection made available, is 80dB(A). The second (upper) action level is 85dB(A) at which the wearing of hearing protection is mandatory and should be enforced by employers as part of their duty to protect the operative.

Types of hearing protection Hearing protectors â€" often referred to as 'hearing defenders' â€" are widely used. Typical protective products available include passive or active earmuffs (either incorporating a headband or helmet-mounted), disposable (with or without cord) earplugs or reusable earplugs. There are even new products entering the market that combine protection such as a combination of earmuff and protective eyewear in the same unit. In Europe, they fall within the scope of the Personal Protective Equipment Directive 89/686, so must be tested and CEmarked before being placed on the market.

Devices meeting only the harmonised European standard EN 352 parts 1, 2 or 3 are examples of passive products â€" without any features for controlling the level of sound attenuation. A range of more sophisticated devices is available which may feature electrical and/or mechanical systems to control the level of sound attenuation or, in some cases, the level of sound attenuation at specific frequencies so that some sounds are cancelled out but the user can still hear speech, e.g. EN 352-4 covers level dependant earmuffs.

Assessment of hearing protectors includes two basic tests â€" sound attenuation and insertion loss. These establish whether the basic requirements are met for reducing harmful levels of noise to acceptable levels at the ear. The sound attenuation test is a subjective assessment using human wearers and is carried out on both earplugs and earmuffs of all types. This testing is carried out in a chamber with closely defined acoustic properties. The other commonly used noise reduction test for earmuffs is 'insertion loss'. This is an electro-acoustic method which compares the level of noise received by a microphone placed in a special test fixture, with and without the hearing protector fitted (human subjects are not used). For active devices more complex test procedures are used.

A range of physical and mechanical tests is also carried out on hearing protectors to assess their basic performance such as fit and adjustment which are important factors for wearer comfort along with other properties such as headband force and cushion pressure.

Selecting the right protection There are advantages and disadvantages that the wearer has to consider when choosing between ear plugs and earmuffs. For ear plugs the benefits include being comfortable to wear for long periods (especially in humid conditions), small, so easy to carry and convenient for working in confined spaces, they also have the advantage of being a low cost, hygienic option for visitors to a site requiring protection. For earmuffs the benefits include easy fitting, less attenuation variability among users and visibility when worn (for monitoring use) and ease of removal when only required intermittently.

They can also be used if the wearer has minor ear infections. Disadvantages of earplugs may include more difficulty for the wearer when fitting and removing, also necessitating good hygiene practices. They can also be easily misplaced and usage may be difficult to monitor due to size. Earmuffs can be less portable, might be dropped and damaged, can be hot and uncomfortable under humid conditions and might make wearing other PPE difficult, such as protective eyewear or prescription glasses.

It is very important that there is a good seal between the ear cups and the wearer's skin. Often a range of earmuffs is needed to accommodate different individuals.

To ensure the most suitable protection it is essential that the wearer is involved in the selection process and that they are trained to ensure that the protection is correctly fitted and worn. A number of factors should be considered including level of noise reduction, comfort, weight and the suitability of the hearing protector for both the worker and his environment.

Surprisingly something as simple as a disposable foam earplug is often not fitted correctly into the ear canal, greatly reducing its effectiveness to protect against noise.