Download in the workplace

Noise
in the workplace
Introduction
This technical bulletin provides general guidance that may be of
use to anyone who is exposed to noise at work. It considers the
legislation that governs the control of noise, the health effects
associated with exposure to harmful levels, some of the control
measures that might be implemented and suggestions of how
these might be validated.
What are the health effects?
The health effects of exposure to harmful levels of noise can be
either acute or chronic. Noise trauma is the name given to the
acute effect suffered after exposure to very loud sounds, such as
those caused by explosions or gun shots. Generally, noise trauma
results in damage to the middle ear with either the ear drum or
the ossicles (the small bones in the ear) becoming physically
damaged. Noise trauma normally predominantly effects high
frequencies, particularly those around 4 kHz and is often
accompanied by tinnitus, a ringing or buzzing in the ears.
Long and repeated exposure to harmful levels of noise can result
in chronic health effects, known as Noised Induced Hearing
Loss (NIHL). Again higher frequencies are most affected,
predominantly at 4 kHz, with the range of frequencies affected
increasing with continued noise exposure. Sufferers of NIHL may
experience difficulty in following conversations, interpreting the
direction of sound and even hearing warnings and alarms. NIHL is
permanent and cannot be reversed.
Legislation
The Control of Noise at Work Regulations set action and limit values
for noise in the workplace.
Table 1 – Action and limit Value
Lower action
value
A daily or weekly personal noise exposure of 80
dB(A) and a peak sound pressure of 135 dB(C)
Upper action
value
A daily or weekly personal noise exposure of 85
dB(A) and a peak sound pressure of 137 dB(C)
Exposure limit
value
A daily or weekly personal noise exposure of 87
dB(A) and a peak sound pressure of 140 dB(C)
The action levels are used to determine which of the duties outlined
in the regulations are applicable, whilst the limit values must not be
exceeded under any circumstances.
Where noise levels reach the lower action value employers are
required to:
• Undertake a suitable and sufficient risk assessment
• Make hearing protection available on request
• Provide employees and their representatives with information,
instruction and training.
Where noise levels reach the upper action value employers are
additionally required to:
•
•
•
•
Reduce exposure to noise to as low as is reasonably
practicable by implementation of a programme of
organisational and technical measures
Provide hearing protection where levels cannot be reduced by
other means
Define hearing protection zones
Carry out health surveillance (where needed).
How can harmful levels of noise be identified?
As a guide, the Health and Safety Executive (HSE) suggest that if
noise is intrusive but normal conversation is possible then noise
levels are likely to be around 80 dB(A), if it is necessary to shout at
someone 2m away then noise levels are likely to be around 85 dB(A)
and if it is necessary to shout to be heard just 1m away than noise
levels are likely to be about 90 dB(A). If noise is at these levels for
6 hours, 2 hours or 45 minutes respectively than a risk assessment
will be needed.
A risk assessment is likely to include a noise survey and this will
certainly be necessary if engineering controls and Hearing Protective
Equipment (HPE) is to be selected accurately. Full noise surveys
are generally conducted using a sound level meter capable of
measuring octave bands (needed to select HPE) and third octave
bands (needed to select engineering controls). Sound level meters
generally measure both Leq which is the average sound pressure
level and LCPeak which is the peak sound pressure level. Different
weightings are applied depending upon the measurements taken;
A weighting is thought to most closely represent the human
response to sound and is used to measure Leq in dB(A), C weighting
is used to measure peak noise levels in dB(C) and Z weighting is
used when taking octave band or third octave band measurements
in dB. These measurements can then be used in calculations or
in HSE supplied spreadsheets to calculate an individual’s daily or
weekly noise exposure in dB(A) and their peak noise exposure in
dB(C) which can be compared to the limit and action values in the
Control of Noise At Work Regulations.
Sound Level Meters:
If an employee is particularly mobile a personal dosimeter may be
used to measure their noise exposure and other simpler devices
which give an indication of noise levels are also available. These
noise indicators are particularly useful to remind employees to wear
their HPE and to monitor noise in a highly variable environment.
Noise Indicators:
3M™ SD-200
Sound Level Meter
3M™ SoundPro™
Sound Level Meter
3M™ Edge™ 5
Atex Dosimeter
Some examples of 3M noise meters are on the right:
3M™ Optime™
Alert Sound Check
How should control measures be selected?
The hierarchy of control should always be followed when
implementing control measures:
1. Elimination or substitution
Careful consideration should be given to the source of noise and
whether it can be eliminated completely by altering the process
used or substituted for something which is less noisy. If this is
not possible, or if noise levels remain at harmful levels,
engineering controls, the next step in the hierarchy of control,
should be considered.
2. Engineering controls
Engineering controls reduce noise at its source or help to prevent its
transmission. Examples of engineering controls include: acoustic
enclosures, damping, vibration isolation and room treatments.
3. Personal Protection Equipment (PPE)
If it is still not possible to control noise to a safe level after following
the upper levels of the hierarchy of control, PPE should be used as
a last resort. PPE may also be used as an interim measure whilst
other controls are being implemented.
3M™ NI-100
Noise Indicator
Table 2 – Some examples of HPE
Roll Down
Earplugs
Also known as
‘Disposable’
• Compatible with other PPE
• Can be stored and distributed
with a dispenser
• Low unit cost
Re-usable
Pods and
Pre-moulded
Earplugs
• No roll down required - easy
to fit
• Re-usable – reduces
replacement costs
• Fitted by using a “stem” – more
hygienic in dirty environments
Banded
Earplugs
• Quick and easy to take on
and off
• Can be stored around the neck
when not required
• Re-usable – pods can be
replaced
Passive
Earmuffs
• Very comfortable
• Easy to fit
• Re-usable – replacement
hygiene kits
Electronic
Earmuffs
• Allows workers to
communicate via site radio,
mobile phone and directly
whilst maintaining protection.
• Stream MP3s or listen to the
radio
• Level dependant function
available
Hearing Protective Equipment (HPE)
There are many different types of HPE and it is necessary to give
careful consideration to selecting a suitable product to ensure that
it is not only able to offer an adequate level of protection but is
also suitable for both the wearer and the task. Table 2 gives some
examples of different types of HPE and some of the advantages of
each type.
The protection offered by HPE is described as its “attenuation”.
Manufacturers of HPE use three different methods to describe the
level of attenuation offered by hearing protection and these can be
compared with measured noise levels in the workplace in order to
select appropriate products.
1. Single Number Rating (SNR)
The effective A weighted sound pressure level at the ear
is calculated by subtracting the SNR value supplied by the
manufacturer from the C weighted sound pressure level that has
been measured in the workplace. SNR is an average across all
frequencies and is not, therefore, as accurate as other methods as
the attenuation offered by HPE varies between different frequencies.
2. High (H) Medium (M) Low (L)
The HML values use A and C weighted sound pressure levels. The
HML method is more representative when choosing HPE as it gives
an indication as to whether the product will provide good attenuation
at the high, medium or low frequencies.
3. Octave Band
The octave band attenuation table is the most accurate form of
identifying the appropriate HPE for the type of noise within your
work place. This requires the A and C weighted sound pressure
levels measured across all frequencies of the octave band.
More information on how to calculate the SNR, HML and
octave band can be found in the HSE’s Control of Noise At Work
Regulations, the HSE website using the noise selector tools, or the
3M website using the hearing selector tool.
Over attenuation, under attenuation and real world attenuation
The European Standard EN458 (Recommendations for care, selection,
use and maintenance) advises that good attenuation for the wearer is
reached when the attenuation at the ear underneath HPE is between
75 – 80dB (A), as indicated in Figure 1 below.
Figure 1 – Good Attenuation
Under Attenuation
Harmful
Good Attenuation
Ideal
Over Attenuation
Isolation
85
Sound level
under hearing
protection (dB)
80
75
70
When HPE is over attenuating it filters out too much sound,
including sounds that need to be heard. This can make the wearer
feel uncomfortable and isolated and may cause difficulties with
communication and the interpretation of warning signals. The
opposite of over attenuation is under attenuation. This is when the
HPE does not offer a high enough level of protection and the wearer is
still exposed to harmful levels of noise.
Attenuation tables provide a good estimate of the attenuation that
could be achieved by HPE in the workplace but the performance likely
to be achieved in the ‘Real World’ may be lower than that obtained
from the standard tests. This may be attributed to poor fitting or
compatibility issues, for example, which can affect the performance of
the hearing protector. For this reason the HSE recommend that 4dB is
added to the calculated sound pressure level at the ear, this is known
as derating.
Training
It is important that employees receive information, instruction and
training on any Personal Protective Equipment (PPE) that is supplied
(as well as other control measures) and 3M can offer a range of
services to help employers fulfil this duty. Hands on training is
available on site from our Hearing Specialist or alternatively 3M
have available a Hearing Conservation Presentation CD or a Noise
Awareness DVD, which can be purchased via your normal 3M
Distributor.
How can protection be validated?
The size and shape of an individual’s ear canal can vary, as can their
ability to fit their HPE. For this reason the attenuation achieved by
one model of HPE can vary between wearers. A method by which
the level of attenuation achieved by an individual can be validated is to
use the 3M EARfit Validation System. The 3M Earfit validation system
uses proprietary algorithms to analyse sound pressure level in the
ear canal, allowing the system to measure a quantitative, objective,
Personal Attenuation Rating (PAR) in just 8 seconds. For more
information on the EARfit validation system please contact 3M on
0870 60 800 60 or visit our website, www.3m.co.uk/earfit_validation
3M Safety Services
3M is able to offer a range of services to help you meet your PPE needs.
These include:
✔ Care & Maintenance Packs
✔ Fit Testing Workshops
✔ Noise Level Check Service
✔ EarFit Validation System (Hearing Protective Equipment)
✔ Hearing Conservation Programme
✔ Air Quality Testing
✔ Respiratory Service Life Software
✔ Product Selection Tools
✔ Fit Testing (Quantitative and Qualitative)
More information from 3M
For more information on 3M products or services please visit the 3M Occupational Health & Environmental Safety website,
www.3m.co.uk/ohes or call our helpline on 0870 60 800 60.
Further reading
•The Control of Noise At Work Regulations 2005
3
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CHNOISETB
Occupational Health & Environmental Safety Group
3M Ireland Limited
3M United Kingdom plc