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|Year : 2003 | Volume
| Issue : 18 | Page : 47--55
The role of hearing protectors in leisure noise
Applied Acoustic Design, United Kingdom
R J Peters
Applied Acousic Design, The Green Business Centre, The Causeway, Middlesex TW18 3AL
Ear muffs and ear plugs are widely used in the workplace to provide hearing protection for employees exposed to high levels of noise. Through an examination of the use of ear protectors in the workplace this paper explores the extent to which these devices can play a similar role in protecting members of the public from hearing damage arising from exposure to high levels of noise from leisure activities.
It is concluded that the major limitation to the effective use of ear protectors for leisure use is likely to be the lack of easily accessible information, advice and guidance on the nature of the hearing protection risk from noisy leisure activities, and on the availability, selection and use of protectors, and of the need for regular hearing checks.
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Peters R J. The role of hearing protectors in leisure noise.Noise Health 2003;5:47-55
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Peters R J. The role of hearing protectors in leisure noise. Noise Health [serial online] 2003 [cited 2021 Nov 29 ];5:47-55
Available from: https://www.noiseandhealth.org/text.asp?2003/5/18/47/31817
In the UK between 0.75 and 2 million employees are thought to be subject to noise exposure levels at work that can cause noise induced hearing loss. Although the use of hearing protectors is regarded as a last resort, only to be used when the reduction of noise exposure by other methods (reduction of noise levels and/or exposure times) is impracticable, in practice the use of hearing protectors plays a major role in the hearing conservation policy adopted by most employers, and ear plugs or ear muffs are worn regularly by hundreds of thousands of employees at work.
Can hearing protectors play a similar role in protecting against leisure noise?
This paper explores this question through a consideration of the use of hearing protectors in the workplace, and considers factors such as the range of devices available, factors affecting the choice of the most suitable type, factors which affect the effectiveness of the protection in use, and, most crucially, the importance of information instruction and education available to the potential user. Finally the possible role of audiometric monitoring is considered.
Noise levels and noise exposure levels
Hearing damage may be caused by:
Prolonged exposure to high levels of continuous noise (above 75 dBA)One off exposure to very high levels of impulsive noise (gunshots, explosions) etc. (Above 200 Pascals)
The best guidance available on noise exposure limits for hearing conservation are to be found in the UK Noise at Work Regulations.
Three Action Levels are defined in the Regulations:
First Action Level: 85 dBA LepdSecond Action Level: 90 dBAPeak Action Level: 200 pascals
[Lepd: personal daily noise exposure level (over an eight hour period)]
As a rough guide to noise levels: if the human voice has to be raised in order to have a conversation between two people at normal conversational distances then this is an indication that the noise level is about 80 dBA or more. The noise level inside a saloon car driven at motorway speeds is likely to be between 75 and 85 dBA. The noise from a DIY electric drill held close to the ear (as when in use), under no load, is about 90 dBA.
It is likely that within a few years the proposed EC Physical Agents Directive will reduce these Action levels to 85 and 80 dBA respectively.
These limits are expressed in terms of noise exposure levels, rather than as noise levels, because the length of time exposed to the noise is important as well as the level of noise itself.
The relationship between noise exposure level, noise level and exposure time is expressed in the 'Equal energy principle' according to which doubling (or halving) of exposure time has the same effect on noise exposure level as an increase (or decrease) in noise level of 3 dB.
Thus a noise exposure of 90 dBA for 8 hours is equivalent to:
93 dBA for 4 hours96 dBA for 2 hours99 dBA for 1 hours102 dBA for 30 min105 dBA for 15 min108 dBA for 7.5 min111 dBA for 3.75 min
The principle is of central importance in determining total noise exposures of individuals throughout a working day, during which noise levels may vary according to the various activities performed. Its relevance to the use of hearing protectors is that it demonstrates that in order to achieve protection against very high levels of noise, protection must be worn all the time. At noise levels of 110 dBA for example, failure to wear adequate hearing protection for only a few minutes will result in an exposure which exceeds one of the Action levels.
Noise exposure from leisure activities
A list of some leisure activities which can give rise to high levels of noise exposure is given in [Figure 1].
For many of these activities hearing protection is best achieved by the direct control of noise levels by the user (eg personal cassette recorders, Hi Fi, Car stereos, Video games etc). In other cases although noise levels are not under the control of the user hearing protection may be achieved through limiting the frequency and durations of periods of exposure (e.g. attendance at Night Clubs, Discos, Aerobics Studios, Pop Concerts, Cinema etc.) although hearing protectors may also be used as well. It is in the third type of activity (e.g. shooting, the use of noisy domestic and D.I.Y. equipment, motor sports and motor cycling) that the use of personal hearing protection will be the main method of hearing protection.
Following a detailed study of leisure noise exposure by the MRC in 1985 (Davies AC et al, 1985) most subsequent research has concentrated on noise exposure and hearing loss from personal cassette players, attendance at night clubs, discos etc and of professional musicians (Smith PA et al 2000; Wright Reid A 2001; Canham R, 1998).
In contrast there appears to be relatively little information on noise exposure and noise induced hearing loss from shooting, motor sports and use of noisy domestic and leisure equipment.
Types of Hearing protectors
The various types of hearing protectors which are available are listed in [Figure 2]. Much more detailed information is available in the publications (Reducing Noise at Work, Guidance on the Noise at Work Regulations 1989; and PrEN 458, Hearing protectors - Recommendations for selection, use, care and maintenance - Guidance document). A list of European Standards relating to ear protectors is given in the bibliography. Some of the advantages and disadvantages affecting choice of plugs or muffs are shown in [Figure 3].
For members of the public exposed to leisure noise ear protectors are available from some high street chemists and DIY stores, and from specialist outlets related to the particular leisure activity, eg motor cycle dealers, and retail outlets at shooting clubs and at motor sports venues, as well as from general safety equipment suppliers.
Some of the specialist types are individually moulded and often aimed at particular types of users such as musicians (both amateur as well as professionals), members of shooting clubs, motor cyclists and at leisure users generally e.g. attendees at pop concerts, night clubs etc.
Factors affecting selection of the most suitable protectors
Certification mark - all hearing protectors sold within EU countries must carry a CE mark, which ensures compliance with the appropriate European Standard.Noise & Sound attenuation requirements as discussed further belowWearer comfort - very important if protectors need to be worn for prolonged periodsCompatibility with any hygiene considerations and medical disorders suffered by the wearerEnvironment and activity ie the protectors must be suitable for the particular use (eg hot, humid conditions, confined spaces etc.)Compatibility with other personal protective equipment, such as helmets, spectacles, respirators etc.Listening requirements ie the need to be able to hear speech or alarm signalsPersonal Choice - an important motivational factor if protectors are required to be worn regularly and continuously for prolonged periods
The selection procedure should be repeated at regular intervals to ensure that an effective Attenuation is maintained.
The Performance of Hearing Protectors
The first essential requirement is that the ear protectors should provide sufficient noise attenuation in order to reduce the noise at the wearer's ear to a level which will prevent risk of noise induced hearing loss. This obviously depends on the levels and frequency spectrum of the noise to which the wearer is to be exposed. Ear plugs and muffs meeting the requirements of BSEN 352 are guaranteed to provide a certain minimum amount of attenuation. This will be adequate for many situations where noise levels are less than 5 dBA above the required Action level (ie 90 dBA in the UK at present, but falling to 85 dBA following the introduction and implementation of the Physical Agents Directive in the future), and other factors, such as comfort and personal choice are more important in the selection process. For higher levels of exposure however, it is necessary to estimate the assumed protection at the ear when the chosen protector is being worn.
In order to do this it is necessary to have information about the sound level and performance data for the protector. A typical set of performance data, in the format as supplied with all CE marked hearing protectors is shown in [Figure 4].
Using this data it is possible to estimate the noise level, in dBA at the ear when the protector is being worn - the 'assumed protected noise level'. From this information, together with the exposure duration, the level of noise exposure (including allowance for the protection provided by the ear muffs/plugs) may be determined.
The methods for estimating the assumed protected level are fully described in BS458, BSEN4869-2, and in HSE Guidance Notes (Reducing Noise at Work, Guidance on the Noise at Work Regulations 1989).
The most detailed and accurate method uses octave band data for both the noise levels and for the attenuation provided by the protectors.
Two shorter, but less accurate methods are also described. The HML method uses one of three attenuation values, depending upon whether, according to the specified procedure the noise is deemed to be High (H) or medium (M) or low (L) in frequency. The HML method leads to a predicted noise level reduction (PNR), which is subtracted from the measured A-weighted sound level in order to calculate the noise level, in dBA at the ear when the protector is being worn.
The SNR method specifies a single attenuation value, the simplified noise level reduction (SNR) which is subtracted from the measured C- weighted sound level in order to calculate the noise level, in dBA at the ear when the protector is being worn.
BS 458 also provides a fourth method, to be used for assessing the sound attenuation of a hearing protector for impulsive sounds, which should be used, for example, in determining the suitability of protectors to be used by people participating in all forms of gunsports.
The amount of attenuation provided by any one type of protector will vary from one person to another depending on individual characteristics such as shape of head or ear canal, leading to differences in quality of fit. Therefore the performance of ear protectors is specified as a mean attenuation together with a standard deviation value.
The various methods described above are all based on an assumed protection value of attenuation of the mean value minus the standard deviation. This means, statistically, that the estimated level of protection is the minimum enjoyed by 84% of the wearer population. It follows, however, that for 16% of the wearers there will be a lower level of protection.
Ideally the aim should be to achieve a level of attenuation such that the noise exposure level at the ear, when the protectors are being worn, is between 5 and 10 dBA below the required Action level (90 dBA at present in the UK, falling to 85 dBA in the future). Overprotection, at more than 15 dBA below Action levels, can give rise to unnecessary difficulties with communication, and uncomfortable feelings of isolation, with the very undesirable result that the protectors are not worn all the time.
Factors which determine effectiveness of Hearing Protectors in use
It must be emphasised that the attenuation achieved by these standard techniques are achieved under optimum conditions, assuming the protectors are in good repair and properly fitted. It has been shown (Hempstock and Hill, 1990) that the performance of protectors in 'real world' use is often much less than suggested by the standard test data either because the protector have not been fitted properly or are worn or defective in some way, or because, even having been fitted properly, the quality of fit has deteriorated during use.
The factors which determine effectiveness of Hearing Protectors in use are summarised in [Figure 5]. The most important of these will be the usage rate, unless a rate which is very close to 100% can be achieved.
The Importance of 100% Usage
The importance of the need for the protection to be worn for 100% of the time exposed to high levels of noise cannot be overstated. No matter how good the assumed protection provided, and this can be in the region of 20 of 30 dB, it will be reduced to only 3 dB if they are only worn for 50% of the time, and even if they are worn for 90% of the time the degree of protection can only be 10 dB. A usage rate of at 99% i.e. not worn for 1% of the time, would be required to achieve 30 dB protection. (Note that 1% of an eight hour day corresponds to about 5 minutes). This is particularly important when the noise levels are very high because the exposure level increases rapidly even in a short time. At a level of 102 dB(A) for example, the second Action level of the Noise at Work Regulations is reached after 30 minutes, and this falls to 15 minutes at 105 dB(A) and 7.5 minutes at 108 dB(A). In these circumstances it is obvious that failure to wear protectors even for a few minutes will be harmful.
It is important that people who should be wearing ear protectors, whether at work or for leisure activities should be aware of these considerations, and therefore important that they should be educated in all aspects relating of the risk to their hearing from noise exposure.
Information Instruction and Training
Under the requirements of the Noise at Work Regulations it is not sufficient that employers should provide employees with suitable and effective ear protectors. It is also necessary that employees should understand why when and how the protectors should be used. Therefore Regulation 11 of the Noise at Work Regulations require that employers provide information to employees about:
The effects of hearing lossThe risk to hearingAvailability of HPsSelection proceduresNoise levels (noise labelling)Effective useHearing checks (Audiometry)
Even so there is often a reluctance among employees to the use of ear protectors, particularly where they are required to be worn continuously for long periods. The programme of information, instruction and training is designed to overcome that reluctance and motivate employees to wear their ear protectors at all time when necessary.
This level of information is not available to members of the public who might be exposed to high levels of noise from leisure activities, and thus an essential component of the hearing protection strategy is missing in this case.
The last stage in a workplace hearing conservation programme is regular audiometric monitoring of employees. This provides the ultimate check on whether the other stages in the programme, such as the implementation of noise reduction measures, purchase of quieter machines and other aspects of noise control management, and the use of ear protectors have been effective.
The requirements relating to audiometry in the Noise at Work Regulations, to be continued in the proposed Physical Agents Directive, have been reinforced by the Management of Health and Safety at Work Regulations 1992, which requires that that employees exposed to certain types of risk, for example high noise levels, should be provided with appropriate health surveillance. Advice to employers (Health Surveillance in Noisy Industries Advice for employers, Leaflet IND(G) 193L) from HSE is that 'it is good practice for employers to carry out regular hearing checks on all employees whose daily personal noise exposure level equals or exceeds 90 dBA, the level at which hearing protection must be worn (under the Noise at Work Regulations)….. The risk of hearing damage rises significantly at exposures above this level. Therefore, even allowing for the use of hearing protection, employees should normally provide hearing checks when noise exposure levels (regularly) reach or exceed 95 dBA''
It is obviously equally important for people exposed at these levels by their leisure activities to also receive regular audiometric checks, even if they wear ear protectors. Unlike the situation for workplace employees, however, there is little by way of publicity and information available to encourage them to do so.
Summary and Conclusions
Obviously, in principle the use of hearing protectors can be equally as effective in protecting against leisure noise exposure as for noise in the workplace. In the a workplace hearing conservation policy there is a framework of expertise, information and advice available to ensure that, as far as possible, ear protectors are always selected appropriately, inspected and maintained effectively, fitted properly and always worn when necessary. There is also a requirement that regular audiometric checks are carried out, to make sure that the use of hearing protection has been effective. This framework of support is not available to potential leisure user.
It is concluded that in order to maximise effective use of Hearing Protectors for leisure use much more information, education and advice needs to be made available to potential leisure users about:
The effects of hearing lossThe risk to hearingAvailability of HPsSelection proceduresNoise levels (noise labelling)Effective useHearing checks (Audiometry)
These conclusions echo similar calls for improved public education about the risk to hearing from high level of noise exposure by the World Health Organisation [Figure 6], and by the US National Institutes of Health Consensus Development Conference on Noise and Hearing Loss [Figure 7].
Bibliography: List of Hearing Protector Standards
PrEN 458, Hearing protectors - Recommendations for selection, use, care and maintenance - Guidance document
EN 352-1, Hearing protectors - General requirements - Part 1: Ear-muffs
EN 352-2, Hearing protectors - General requirements - Part 2: Ear-plugs
EN 352-3, Hearing protectors - General requirements - Part 3: Ear Muffs attached to an industrial safety helmet
EN 352-4, Hearing protectors - Safety requirements and testing - Part 4: Level-dependent ear-muffs
EN 352-5, Hearing protectors - Safety requirements and testing - Part 5: Active noise reduction ear-muffs
EN 352-6, Hearing protectors - Safety requirements and testing - Part 6: Ear-muffs with audio communications
EN 352-7, Hearing protectors - Safety requirements and testing - Part 7: Level dependent ear-plugs
EN 13819-1, Hearing protectors - Testing - Part 1: Physical test methods
EN 13819-2, Hearing protectors - Testing - Part 2: Acoustic test methods
EN 457:1990, Danger signals for workplaces - Auditory danger signals
EN 24869-1:1990, Acoustics - Hearing protectors - Part 1: Subjective method for the measurement of sound attenuation (ISO 4869-1:1990)
EN 4869-2:1995, Acoustics - Hearing protectors - Part 2: Estimation of effective A-weighted sound pressure levels when hearing protectors are worn
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