Hearing protection

The risk to hearing

Excessive exposure to noise causes irreparable damage to your hearing. Often the damage gets gradually worse with each repeat exposure, but some very high level sounds, such as those from gun fire and explosions, can cause immediate damage.

Damage from long term exposure

Long term exposure can arise from regular working in a noisy occupation or workplace. Receptors that provide the signal from the ear to the brain are damaged by excessive noise, often without the sound seeming too loud or painful. The receptors do not recover. Over time more receptors are damaged, increasing the hearing loss. The risk to any individual is normally determined by their A-weighted daily or weekly personal noise exposure (the overall amount of noise in terms of level and duration in a working day or week).

Very high level sounds, such as fireworks, gunfire or explosions can result in injury that causes immediate hearing loss or other hearing damage. The risk of instantaneous damage is normally determined by the maximum instantaneous C-weighted peak sound pressure of the sound.

When and where hearing protection is required

Requirements of the EU Physical Agents (Noise) Directive

The EU Physical Agents (Noise) Directive provides the minimum basis for national Instantaneous damage laws within the European Union on protecting workers from the risks of noise. This directive defines lower and upper action values and limit values, in terms of the daily or weekly personal noise exposure level and the maximum instantaneous C-weighted peak sound level (see Table 1.

The daily personal noise exposure level (sometimes called LEX,8h or LEP,d) is a measure of a person’s total noise exposure in terms of both level and duration during the working day. This value is expressed as the continuous sound level that would give the equivalent exposure within an 8 hour period. The weekly personal noise exposure level is the average of the daily noise exposures during the week. Because decibels are logarithmic, calculation of noise exposure levels is best accomplished using specific calculators.

The maximum C-weighted peak sound pressure level is an instantaneous value. It can be indicated by a sound level meter or dosimeter with a suitable peak level indicator.

When there is no alternative means of preventing a hazardous noise exposure, then the Directive requires that appropriate and properly fitting individual hearing protectors are made available. These should be available to all workers whose noise exposure exceeds the lower exposure action values while those whose exposure is at or above the upper action values must use the hearing protection. The protectors must provide sufficient protection to reduce the exposure at the ear below the limit value.

Using a risk assessment to identify those at risk

A risk assessment is necessary to identify who is exposed above the lower or above the upper action values and the work locations and tasks that significantly contribute to their exposure. Risk assessments should identify those who need hearing protection, how much protection is required, and when and where it must be used.
The daily personal noise exposure of each individual can be calculated from the noise level and duration of each noisy task within their working day, or by measurement of the person’s exposure over the working day using a sound exposure meter (noise dosimeter). If a noise dosimeter is used, one that provides a logged record of how the sound level varies with time will aid identification of the significant noisy periods and tasks when hearing protection may need to be worn.

It is important in the risk assessment to consider safety factors when hearing protection is to be used. Hearing protection reduces a person’s ability to hear warning sounds. You might need, for example, to consider alarm audibility, safe working during vehicle movements or speech communication.

Adequate protection is essential, but excessive attenuation (over protection) and requiring use where protection is not required should be avoided.

Selecting the best protector

All protectors should bear the CE certification mark if used to control exposure in the workplace. This marking confirms the protector meets the requirements of the European directive 89/686/EEC on personal protective equipment (normally based on the standards in the EN 352 series).

The types of hearing protector

Earmuffs

Figure 1: Earmuffs worn with band over the head, and behind the neck with supporting head band

Earmuffs have hard plastic cups with a cushioned seal and a sound absorbing lining. The cups are held firmly over the ears with a tensioned headband. Earmuffs are easy and quick to put on, and are clearly visible when worn. It is important that the tensioned head band is worn correctly. The headband is usually worn over the head but some earmuffs have a tensioned headband that is worn behind the head. Where this is the case a second supporting band is normally worn over the head. If earmuffs can be worn in either orientation the performance may be different in each orientation.

Helmet mounted earmuffs

Figure 2: Helmet mounted earmuffs

Some earmuffs mount directly onto helmets. These can provide a more reliable performance and fit than separate helmet and earmuffs. However some helmet and earmuff combinations on the market only fit a limited range of head sizes and it is worthwhile checking for any limitations before these are bought.

Earplugs

Figure 3: Earplugs, corded earplugs and banded earplugs

Earplugs are worn in the ear, normally in the ear canal or over the ear canal entrance. They provide protection by sealing the ear canal. Some earplugs may be fitted to a cord or tensioned band. The fit of earplugs is not normally adversely affected by other head-worn clothing and personal protective equipment, but they can be difficult to fit correctly. It is important to follow the manufacturer’s instructions for fitting and most users will require some initial help and training.

Earplugs can work loose and users will need a quiet place where they can refit them. Earplugs should be fitted with clean hands so their use may be inappropriate in dirty or dusty workplaces.

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Custom moulded earplugs

Figure 4: Custom moulded earplugs

Custom moulded earplugs can be easier to fit, but they will perform poorly if the fitting or moulding is incorrect. Manufacturer’s fit tests on the individual wearer are essential before the earplugs are used, and regular repeat fit tests are often required during the lifetime of the protector.

Dual protection

Where an earmuff or earplug on its own cannot provide sufficient attenuation an earplug and earmuff can be worn together (dual protection). Unfortunately, the attenuation of the combination cannot be predicted from the attenuation data of the earmuff and earplug when used alone. Attenuation data measured for the combination is required. Manufacturers can provide data for some earplug and earmuff combinations, but choice is limited.

Special features

Some hearing protectors are equipped with electronic features to aid communication or reduce the attenuation of the protector in quiet periods. Others use electronic features to provide additional attenuation. Mechanical filters are also used to provide a flat frequency response in some protectors.

Sound restoration protectors

Sound restoration protectors use an electronic sound system to relay outside sound to the ear, bypassing the protector. In CE marked devices the system gain should ensure the restored sound remains at a safe level and that full attenuation is provided in high level sound. These devices are useful with intermittent high level noise such as gunfire, where they allow the wearer to clearly hear sounds around them when it is quiet while providing immediate protection when a gun is fired.

Communication protectors

Communication protectors provide wired or wireless communication within the protector and can be useful for team communication or for entertainment radio. CE marked communication protectors designed for essential communication may provide sound at potentially hazardous levels to ensure adequate audibility. Devices designed for entertainment only will be limited to a safe level. It is important to check before they are used that these devices do not mask warning sounds and alarms.

Flat response protectors

Most protectors provide more attenuation at high frequencies than at low. This makes sounds muffled and distorted and reduces the clarity of speech. Flat frequency response protectors using mechanical filters are available as low to moderate attenuation protectors. They are often aimed at musicians but are useful for anyone who needs to hear with maximum clarity and minimal distortion while using hearing protection.

Active noise cancellation

Sound of equal level but opposite phase can be used to cancel sound. Active noise cancellation is available with some earmuffs to provide enhanced attenuation. It is effective at low frequencies up to around 500Hz. Earmuffs of this type are typically used in air and military transport.

Selecting the right amount of protection

A hearing protector must prevent exposure above the limit value, and should also reduce noise exposure to below the upper action value, preferably below the lower action value. If workers have variable exposures you should ensure the protectors are adequate for the worst case situation likely to be encountered. Protectors that reduce exposure by more than 15dB below the upper action value are normally considered to provide excessive or over protection. If workers are overprotected they will experience unnecessary isolation and difficulty hearing. They may choose to remove the protector, and risk hearing damage.

The attenuation provided by any protector depends on the protector attenuation characteristics and the frequency content of the noise. There are three standard methods for estimating the level at the ear when hearing protection is worn, each using different noise measurements and data sets for the protector. Table 2 summarises these.

It should be noted that calculators may de-rate the attenuation result. Any de-rating is optional. De-rating is used to represent the workplace performance where fit and use may be less than optimal. Other methods of obtaining an estimate of the workplace performance may be recommended in national guidance. In some cases it may be possible to maximise workplace performance so that a de-rating is inappropriate.

The modified H, M and L values used for the assessment of hearing protector performance against peak noise include a de-rating. An additional de-rating is not normally applied.

Selecting for the work environment and compatibility with other personal protective equipment

The work activity, environment and any other personal protective equipment used will affect the style of hearing protector required.

• Is voice communication required? Consider communication or flat response protectors.
• Is the user moving between noisy and quiet areas, or are hearing protectors required during intermittent noise? Consider if user safety would be improved with sound restoration protectors.
• Is it important to retain the quality of the sound heard? Consider using flat response protectors (often sold as hearing protection for musicians).
• Is the exposure pattern made up of short term, repeated periods? Earmuffs are more easily fitted and removed than earplugs.
• Will the user need to use other head worn clothing or personal protective equipment? Earplugs or integral earmuffs (such as helmet-mounted earmuffs) or compatible earmuff and personal protective equipment combinations should be preferred.
• Is the wearer working in a dirty environment? The need for hand washing facilities should be considered if earplugs are used.
• Are wearers working in extremely low temperatures, possibly below -20oC? Normal earmuffs may not function correctly, and low temperature earmuffs will be required.

Selecting for personal needs and comfort

No single type of hearing protector will suit all users. It is important to provide a choice of suitable protectors and allow workers to choose what they find most comfortable. If possible include both earmuffs and earplugs in the choice, and include variety in both the size and style. Users will need to select according to:

• Comfort
• Ease of correct fitting
• Ability to hear and work while wearing the protector
• Existing hearing impairment.

Comfort may be physical comfort and social comfort. No one should be asked to wear a hearing protector for long periods that causes discomfort. If the wearer is self-conscious about the appearance of the hearing protection it is unlikely to be used effectively. Unobtrusive protectors might be preferred by those working in public places such as music and entertainment venues where appearance is important.

Correct fitting can be difficult with earplugs especially if the user has narrow or crooked ear canals. Problems can sometimes be resolved with training on fitting, as well as having a suitable range of earplugs to try. Custom moulded earplugs may also provide a solution.

It is important to ensure all hearing protector users can still hear well enough to work safely. Special care will be required if the protector user is deaf and needs to use hearing aids. A protector that can be worn with the hearing aid should be considered. It is not appropriate to require a person to remove a hearing aid in order to wear hearing protectors.

Ensuring best use in the workplace

It is expected that hearing protection will give lower attenuation in the workplace than that predicted by the manufacturer’s data. This can be due to poor fit, the effect of other personal protective equipment and clothing, removing of the protector in the noisy environment and ageing of the protector.

To ensure effective use a full hearing protection programme is required to ensure workers make full use of hearing protection, fit it correctly, and hearing protectors are kept in good condition.

Consultation and training

Workers and their representatives must be consulted over the introduction of hearing protection. This is an opportunity for workers to highlight problems and contribute to finding practical solutions.

Training is also required for each hearing protection user. This should cover:

• the risks of noise in their workplace and the purpose of using hearing protection;
• when and where hearing protection should be worn;
• how to look after the protectors;
• how and when to obtain replacement protectors;
• correct fitting of the protector.

Fitting hearing protection

Earmuffs

Earmuffs can be fairly easy to fit but it is important to ensure there is no break in the seal around the ear and the headband tension is firm. Fit the earmuff in the correct orientation making sure that jewellery and hair does not interfere with the seal. Spectacle frames usually have an insignificant affect but, it is important to avoid large frames that lift the cup seal from the head and look for muffs with softer seals. Earmuffs should not normally be worn over hats and hoods unless these are specifically designed to be worn under earmuffs without significantly reducing the attenuation.

Earplugs

It is important to follow the manufacturer’s instructions during fitting. The following tips may also be useful:

• Compressible foam earplugs will usually require compressing using a rolling action to make them thin enough to insert deeply into the ear canal. The earplug then expands to fill the ear canal. Squashing and pushing the earplug into the canal will result in a very poor fit.
• When inserting an earplug pull back and slightly upwards on the outer ear (the pinna). This straightens the ear canal so the earplug can be more easily inserted.
• Once in a noisy place the wearer can check the fit in two ways:
  • If the earplug has no sound filter put your hands over your ears while wearing the earplugs. If this action changes the sound the earplug is poorly fitted.
  • If the earplug has a filter, block the filter opening with a finger. If you hear no change in the sound when the filter is blocked the earplug is possibly poorly fitted.
• There are devices available that provide an indication of the earplug attenuation achieved by an individual. These can be useful for improving fitting. However, the actual attenuation result may not be reliable as there are no standards for these devices yet.

Checking the audibility of warning and essential sounds

Hearing protection reduces the audibility and clarity of sounds; this may put users at risk. Check that, when workers have hearing protectors fitted, they can clearly hear essential sounds such as alarms, vehicle movements around them, machinery and shouted speech. A listening test should be made to check each person can still hear and respond to sounds, particularly when not expecting to hear them.

Where audible warnings are difficult to hear they can be reinforced with visual or vibrating indicators. Alarms can also be linked to the signal sent to communication protectors.

Those with a hearing impairment still require hearing protection. Special care will be required to ensure they can work safely when using protectors. Some workers find that tubes to the hearing aid earpiece fill with moisture when worn under an earmuff, blocking the sound. If a hearing aid user finds it easier to remove the aid when wearing hearing protection sound restoration protectors may provide them with some useful amplification during quiet periods.

Maximising performance through full use

Hearing protection must be worn at all times in a noisy environment. This is particularly important if the peak action values are exceeded as workers risk immediate injury if unprotected.

The effective protection against the daily or weekly exposure also quickly reduces if the protector is removed while in a hazardous sound level. Table 3 gives effective protection for different time periods spent without wearing a hearing protector during an eight hour day where exposure is continuous. It is assumed the protector provides 30dB attenuation if worn continuously.

Assumes protection is required throughout an 8 hour day.
Source: author

Keeping protectors in good condition

• Earmuffs and reusable earplugs should be checked regularly to ensure they are in good condition. They should be kept clean, following the manufacturer’s instructions. Hearing protectors that have deteriorated should be replaced and replacement protectors should be available at all times.
• Check earmuff cups and seals are intact. Seals should be flexible, but may become stiff and brittle with age and use. The headband tension can slacken with use. Check the tension by comparison with a new pair of earmuffs.
• Helmet mounted earmuffs should not be stored with the earmuffs pressed against the helmet. This can permanently distort the seals.
• Disposable earplugs should only be used once. New earplugs should be kept ready for use in a dispenser that keeps them clean and dry.
• Each worker should be provided with suitable storage for their hearing protectors.