132 used for defining designated areas, provided it can be shown that the
noise exposures are consistently below the noise exposure limit. Noise levels may be determined using a simple sound level meter Type 1 or
Type 2, but it is essential that the instrument is used correctly if meaningful data are to be obtained, e.g. attention to calibration, account taken of type of
noise, etc. In workplaces where the noise levels fluctuate e.g. workshop areas the
survey should establish the typical full shift individual noise exposures for the jobs concerned for comparison with the noise exposure limit. For those jobs
or job elements for which the limit is normally expected to be exceeded, suitable hearing protection should be worn.
Apart from checking compliance with an exposure criterion, noise exposure measurements are also useful for indicating priority areas for noise control, for
highlighting those personnel most at risk, and for hearing conservation education purposes.
13.11.2 Control of Workplace Noise
Where engineering control is indicated to minimise workplace noise, the following general approaches are recommended, in decreasing order of
preference:- Reduction of noise at source - best achieved at the design stage.
Enclosure of noisy equipment - although heat dissipation and access
for maintenance can be a problem. Screening of noisy equipment from the worker andor increased
separation of the worker from the noise sources. Absorption of sound by the cladding of appropriate surfaces with sound
absorbent material where reverberation can be a problem. These measures should be coupled with regular maintenance of machinery
as this can contribute significantly to minimising noise emission.
133 Noise specifications should be developed for all new machinery. These
should take account of the existing workplace noise environment and the prevailing noise exposure limits.
13.11.3 Protection of Personnel at Risk
It is necessary to protect the worker from exposure to excessive noise in the work environment if engineering measures andor other means of control are
insufficient or not reasonably practicable. One or more of the following approaches may be adopted:
Provision of Noise Refuges in designated areas, e.g. in boiler houses. If 50 per cent of the working day is spent in the acoustic refuges,
exposure is effectively halved – that is, the noise dose is reduced by
3 dBA. Alteration of the Work Pattern, e.g. via job rotation although this may
be difficult to administer to reduce the exposure time in designated areas and so reduce exposure.
Use of Personal Hearing Protection Devices, e.g. ear muffs, ear plugs. The appropriate selection, correct use and regular maintenance of
these devices are of paramount importance to ensure that efficient protection is achieved. Where available, real-world attenuation data
should be taken into account in the selection procedure. 13.11.4 Information Instruction and Training
All persons who are potentially exposed to noise at work in excess of the noise exposure limit should be instructed in the risk of hearing loss, the
preventive measures and their role in the hearing conservation programme. The instruction may be given in various ways, for example:
Courses for new employees and the issue of written guidance. Periodic revision courses for those who work in designated areas.
On-going line management action to explain the hearing conservation
policy to persons and groups at risk. Periodic hearing conservation campaigns including competitions,
films and posters.
134 Instruction to employees potentially at risk should include information on:-
The nature of noise and the mechanism of hearing. The effects on hearing of exposure to noise in excess of the noise
exposure limit. The principles of hearing conservation.
The requirements for the effective implementation of the hearing
conservation programme.
135
14 VIBRATION
14.1 Introduction
