This document is a copy of the page http://www.hmso.gov.uk/si/si1989/Uksi_19891790_en_2.htm
The US regulations are more lenient with respect to lound sounds. They
are approximately equivalent to demanding that the average
square root of the energy not exceed 90dB for an 8 hour duration. It stipulates
that each extra 5dB in average
energy -- ie, each increasei by a factor of 3.2 in average energy--
decreases the allowed exposure time
by a factor of 2. Thus under the US regulations, a 120dB sound could be tolerated
for 7 min (8/64 hours), while the European regulations would allow this for only
30 sec (8/1024 hours) in a day the rest of which was quiet. Most rock concerts
and many discos exceed even the linient US standard.
I know of no justification for treating these loud noises more leniently.
The justification given is that the ear can compensate for short exposures to very loud
sounds, but my impression is that the evidence for this is sparse.
[End of note]
The Noise at Work Regulations came into force in 1990 and they aim to protect workers from the risk of hearing damage due to excessive noise. How do these regulations affect theatre personnel? In consultation with the ABTT 's Sound Committee, Simon Kahn reports .
The regulations set a maximum daily 'dose' of sound energy (LEP,d) of 90 dB which should not be exceeded. If this level would otherwise be exceeded, the employer must attempt to reduce the sound or transmission path or failing this, create a 'noise zone' in which hearing protectors must be worn. A lower level of 85 dB is set at which employees are entitled to hearing protection on request, and the employer must provide information.
The regulations are geared to a workplace where there is a regular pattern of work such as a production line. In the theatre the varied nature of productions and workload makes assessment difficult, except for West End shows, and the regulations cover all noise 'at work' so the exposure of freelance or self employed work should include all their work activities.
A daily dose of 90dB would cause hearing damage in approximately 60% of the population if they were exposed to the same level every working day for 40 years. The regulations make no distinction between 'music' and 'noise'. The EEC are proposing to introduce new regulations, with action levels starting at 75db, which will bring a lot more activities under the scope of the regulations.
Where a work place has a fairly constant activity over a period of time, the procedures laid down give a reasonable assessment of the employees' likely exposure. In the theatre, where activity is much more varied, the prescribed measurement procedure may not be a good reflection of the likely exposure, but this does not affect the requirements to comply with the legislation.
Three action levels of exposure – first(Lepd=85dBA): second (Lepd=90dBA): Peak (200Pa) are defined. The daily exposure level can be measured directly using a noise dose meter or calculated from a series of measurements. If the first or peak action level might be exceeded a noise assessment must be made by a ‘competent person'. The Assessment must be reviewed when the work assessed changes. A competent person does not have to be a specialist. A number of centres offer training courses leading to a certificate of competence, but the certificate is not obligatory.
If the second action level is exceeded the exposure should be reduced, as far as practicable, by means other than ear defenders. Ear defenders must be provided to all employees if the second action level or peak action level is still exceeded and on request if the first action level is exceeded, The ear defenders must be suitable for the particular noise, be maintained, worn and the zone where they are needed must be clearly marked.
If the first or peak action level is exceeded the employer must provide information and training on hearing protection.
The regulations allows a certificate of exemption to be issued by HSE allowing the second level to be determined by the weekly exposure where the work fluctuates on a day to day basis < 90 dB(A) although in July 1997 no exemptions had been issued at all!
The NAWR also require manufacturers and suppliers of equipment to provide adequate information about the noise where the equipment may cause an employee to be exposed to the first or peak action levels.
NAWR and Theatres
1. Hearing damage is cumulative and the effects of hearing damage are often not noticed until many years later when loss of hearing due to ageing exposes the damage. Hearing damage is also irreversible. However, hearing does fluctuate due to colds and other illnesses, and loud sounds may produce a temporary threshold shift with no permanent after effects (e.g. after a rock concert). Apart from extremely loud sounds, which can cause immediate injury, the acceptable level of noise exposure depends on the level of the noise and the time of exposure. Sound level and exposure level are usually measured exponentially in decibels (dB). A 10dB increase in level increases the exposure level by 10dB and each doubling of the time exposure increases the exposure level by 3dB. For example, exposure to 90dB(A) for 8hours is equivalent to exposure to 99dB(A) for 1 hour. Measurements are made A-weighted to approximate to the frequency sensitivity of the ear.
2. The trigger point for NAWR is "when any ...employee is likely to be exposed to the first (or peak) action level or above" R4(1).
Guide 1 section 23 (G1-23) suggest that as a rough guide, if two people have to shout or have difficulty communicating when standing 2m apart, a noise assessment should be made. This assumes that the sound level is constant for a normal working day. In the theatre the sound levels are very rarely constant for a working day and it is difficult to make a simple rough guide. Areas for concern are sound technicians working long hours preparing sound effects or amplified music, musicians in pits and pyrotechnics.
For a thirteen hour production day, the first action level would be exceeded by a continuous sound level of 83dB, not 85dB.
3. Once a noise assessment has been made it should be reviewed when the work assessed changes. This means that the assessment may need to be repeated for each new production, and even during production periods. There is no provision to 'drop out' from assessment once an assessment has been made although there is not a requirement to actually measure for each assessment.
4. Measurements can be made using 'clip-on' noise dose meters or integrating sound level meters. Because of the varied nature of the sound levels, movement of staff and working hours, an assessment will require more than simply making measurements. For varied activities, a noise 'dose' can be established for each activity and these levels combined according to Noise Guide 3 para. 29 (G3-29). Making an assessment will probably involve a specialist who can interpret results and advise on any necessary actions. This need not exclude a sound technician from actually making measurements, both for the assessment and to ensure compliance. NAWR requires records to be kept of measurements taken.
5. When a production tours, noise measurements made in one theatre may not be the same as in another. This will depend on the size of the auditorium, the amount of backstage space, the reverberation times of stage and auditorium, and the size of the pit if in use.
6. If an assessment is made, theatres may benefit from applying for exemption from daily levels to weekly levels in borderline cases. For example, if a single performance has an LEP,d of 87dB(A) on matinee days the LEP,d will be 90dB(A), the second action level. Over a week of 8 performances the LEP,w will be 89dB(A).
7. Measurement methods for peak action levels are not clearly defined although a rough check can be made using a fast reading sound level meter (not integrating, as required for LEP,d measurements). If a reading over 125dB(A) is made further measurement is necessary. Peak action levels may be exceeded when pyrotechnics are used or in drum booths.
8. Where action levels are exceeded, most theatres will wish to reduce noise exposure without compromising the noise levels set during the design process.
The best method of doing this is by managing the noise. This can be done by:
a) placing loudspeakers so that employees are not exposed to louder levels than the audience.
b) ensuring that as few staff as possible are on stage when the production is noisy.
c) rotating staff duties so that they are not exposed to loud noises each performance
d) ensuring that staff involved in noisy work have quiet breaks.
9. Zoning and hearing protection may be required where pyrotechnics or very loud sound effects are required. Legally and practically, they are a last resort. They also trigger a requirement for training and information. Where pyrotechnics must be operated with line of sight, there may be no alternative. If hearing protectors are used, octave band analysis of the noise hazard will need to be made.
10. The production period is not well covered by the NAWR provisions, as the work is not repetitive. The regulations do not allow for a planning process to reduce noise (such as that for building noise: BS5228) but this is in practice the only way to limit noise exposure during the production period, especially as long hours are often worked. It is common practice to keep production periods as quiet as possible and this should be encouraged. Where possible noisy work should be scheduled to minimise general exposure and all unnecessary staff encouraged to leave the noisy area.
11. Musicians, including freelancers are definitely employees and covered by the regulations. Employers' duties include freelance staff and people employed elsewhere, so consideration should be made, for example, of musicians employed by a theatre in the evening but teaching or playing all day as well. If musicians set their own monitoring level, care should be taken that this will not exceed action levels. Research has found a difference in hearing between violinists' left and right ears, so it should not be assumed that it is only brass, percussion and electric instruments that can cause high exposure levels.
12. There is no agreed method for measuring noise dose from headphones although broadcasters are beginning to limit headphones to 'safe working levels'. Headphones are available with built-in limiters (e.g. Canford Audio).
13. Employers also have a duty where employees visit other sites and this includes riggers, touring and maintenance crews who visit different sites, even in the same day. Apart from equipping all staff with personal dose meters, it is difficult to see how such a varied work load can be monitored.
14. Sound engineers should be particularly careful when preparing sound effects. Listening at high level should be kept to an absolute minimum. Spreading the work, so that work is not all done on the same day, can help to reduce exposure. A loud sound effect at a level of 110dB (a baby crying can make that noise!) can be listened to for only five minutes before exceeding the second action level.
15. Separate regulations (Management of Health & Safety at Work Regulations 1992) require hearing testing (audiometry) for employees if the unprotected exposure LEP,d is above 95dBA. Although expensive, where the workforce is mobile, and the workload varies, audiometry can have a number of advantages:
a) Screening can identify workers with non-occupational medical problems, improving welfare.
b) Employers can be aware of workers who have been exposed to noise hazards elsewhere, either at work or leisure.
c) Employees may be reassured that their hearing is not being damaged whilst at work.
Audiometry does not reduce noise exposure or an employers liability and requires measurement of a number of workers over a period of time to produce meaningful results. Individual audiometry test results are medical records and covered by confidentiality, although it is in the interests of both the employer and employee to co-operate with any audiometric measurement programme. A comparison of audiometry results for a large number of sound and other theatre technicians with other industries may show if theatres are generally noisy workplaces.
16. HSE have published a 'Pop Concert Guide ' which states that the audience is not covered by NAWR, but suggests a maximum Leq of 106dB for the audience. This guide is currently being reviewed (1997).
Note: this does not exempt members of the audience who are 'at work' e.g. ushers, artists, production staff, sound engineers or (?) critics.
Summary
Sound technicians should be aware of the risk of hearing damage and of the NAWR. They may be asked to take, or assist in the taking of, measurements for a noise assessment. Where possible, timetable and equipment planning should avoid prolonged exposure to loud sound levels. Where the second action level is exceeded, hearing protectors must be worn. Assessments must be made by 'competent persons' and need to be reviewed when productions change.
Sound technicians should seek information from suppliers of equipment likely to cause sounds over the first or peak action level. One practical way to manage sound exposure levels in the theatre may be to create a database of noise exposure for different tasks and productions, similar to BS5228 (the method for calculating construction noise).
Finally it should be remembered that many theatres' workload varies considerably, some on an annual pattern, but the NAWR are based on daily exposures although a weekly exposure may be used with written permission.
The Health & Safety Executive (HSE is responsible for enforcing the regulations) have produced the following table:
(LAeq) over exposure period Exposure time to reach an LEP,d
87 dB(A) 16 hours
90 dB(A) 8 hours
93dB(A) 4 hours
96 dB(A) 2 hours
108 dB(A) 7.5 minutes
The Legislation
The NAWR 1989 SI:179 are a statutory instrument empowered under section 15 of the Health & Safety at Work Act 1974 (HASAWA) to meet the requirement of EC directive 86/188/EEC. Note that HASAWA has a general requirement for the protection of health and noise and vibration are recognised as occupational hazards and can be dealt with under the act - fulfilling the requirement of NAWR does not in itself protect you from the general scope of HASAWA.
In addition to the regulations, the HSE has published Noise Guides 1-8 in two volumes (1-2 & 3-8) giving advice and information. These noise guides are the main points of reference for most people concerned with noise at work but it is the regulations that have legal effect. Guides 1 & 2 contain the regulations and advise on legal duties. Guides 3-7 are concerned with measurement and control of noise. Guide 8 deals with exemptions.
Summary of Regulations
Regulation 1 (R1) is administrative.
R2 (1) defines "daily personal noise exposure" (according to a later schedule, "exposed" as meaning exposed whilst at work) and first, second and peak action levels.
R2(2) includes the self-employed as employers and employees and extends employers duties to employees to "any other person at work".
R2(3) extends the employers duties to managers of mines & quarries!
R2(4) is administrative.
R3 excludes the employers, master and crew of ships, Hovercraft and aircraft.
R4(1) requires an employer to ensure a competent person makes a noise assessment when any employee is likely to be exposed to the first or peak action level. The assessment must
a) identify which employees are exposed and
b) provide information to facilitate compliance with R7-9 & 11.
R4(2) requires the noise assessment to be reviewed when
a) there is reason to suspect it is no longer valid; or
b) there has been significant change in the work to which the assessment relates.
R5 requires the employer to keep adequate records of an assessment made until a further assessment is made.
R6 places a general duty on employers to reduce the risk of hearing damage to employees to the lowest level practicable.
R 7 requires employers, if the second or peak action level is exceeded to reduce the exposure of employees as far as practicable without the use of hearing protectors.
R8(1) requires employers to provide employees exposed between the first and peak action levels, at their request, suitable hearing protectors.
R8(2) requires employers to provide employees exposed above the second or peak action levels with suitable hearing protectors to reduce the exposure to below the second or peak action level.
R9(1) requires employers to establish marked ear protection zones where hearing protectors must be worn.
R9(2) defines such a zone as where the second or peak action level will be exceeded.
R10(1) requires employers to ensure any protection measures are used and maintained.
R10(2) requires employees to properly use protection measures and report any defects to the employer.
R11 requires employers to provide employees likely to be exposed to the first or peak action levels with information, instruction and training on
a) the risk of hearing damage,
b) steps the employee can take to minimise damage,
c) how to obtain hearing protectors, the employers obligations.
R12 requires manufacturers and suppliers to provide noise information where equipment may cause the first or peak action levels to be exceeded.
R13 allows the HSE to exempt employers by certificate where the daily exposure exceeds the second action level but the weekly exposure does not.
R14 allows the Secretary of State for Defence to exempt the Forces.
R15 is administrative.
Noise at Work Regulations 1989 HMSO
Health & Safety at Work Act 1974 HMSO
Management of Health and Safety at Work Regulations 1992 HMSO
Noise Guides 1& 2 HSE
Noise Guides 3-8 HSE
Introducing the Noise At Work Regulations (free leaflet) HSE
Guide to Health Safety and Welfare at Pop Concerts and Similar Events HSE
Certificate of Competence courses Institute of Acoustics, St Albans.
BS EN 352 Hearing protectors. Safety requirements and testing. Ear plugs
BS EN 458 Hearing protectors. Recommendations for selection, use, care and maintenance.
BS EN ISO 3746 Determination of sound power levels of noise sources using sound pressure.
BS 4196 Sound power levels of noise sources.
BS EN ISO 4869 Acoustics. Hearing protectors. Estimation of effective A-weighted SPL's when hearing protectors are worn
BS 5228 Noise control on construction and open sites.
BS 5330 Method of test for estimating the risk of hearing handicap due to noise exposure
BS EN ISO 11200-204 Acoustics. Noise emitted by machinery and equipment.
BS EN 24869 Acoustics. Hearing protectors. Sound attenuation of hearing protectors.
BS EN 60651 Specification for sound level meters
BS EN 60804 Specification for integrating-averaging sound level meters
BS EN 61252 Specifications for personal sound exposure meters
BS 6655 Specification for pure tone air conduction threshold audiometry for hearing conservation purposes