|
What is Noise?
Occupational Noise
Regulations and Standards
Hearing Protection
Noise Control
Noise Measurement
Environmental Noise
Ototoxins
Consultnet
Noise Consultancy Services
What is Noise?
Noise is typically defined as "unwanted sound", sound being the
human sensation of pressure fluctuations in the air. Sound levels are expressed
in decibels (dB) on a logarithmic scale, where 0dB is nominally the "threshold
of hearing" and 120dB is nominally the "threshold of pain".
Depending upon the
circumstances and characteristics of the sound in question, a change in level of
3dB is just perceptible, whereas an increase of 10dB is perceived as a
subjective doubling of loudness (as noise is measured on a logarithmic scale).
The
frequency of sound is the rate at which a sound wave oscillates, and is
expressed in Hertz (Hz). The frequency of a sound produces it's distinctive
tone. The rumble of distant thunder has a low frequency,
while a whistle has a high frequency. The normal
range of hearing for a healthy young person extends
from approximately 20 Hz up to 20 000 Hz (or
20 kHz) while the range from the lowest to highest note
of a piano is 27,5 Hz to 4186 Hz. The sensitivity of the human ear to different
frequencies in the audible range is not uniform. For example, hearing
sensitivity decreases markedly as frequency falls below 250Hz.
A mechanism known
as "A-weighting" has been adopted in order to account for this non-linearity of
the human ear. Sound levels expressed using "A-weighting" are typically denoted dB(A). An indication of the level of some common sounds
is shown below:
Noise levels are usually assessed in terms of
A-weighted decibels (dB(A)).
If you have to shout to get yourself heard
the background noise level is 75-80dBA. An average living room
would typically have a noise level of about 40dB(A) while busy road traffic
would generate about 70-80dB(A) measured on the pavement (approx 3m from the
vehicles).
For more examples listen to
the
NIOSH online noise meter
The study of sound is called
acoustics and covers all fields of sound
production, sound propagation and sound reception, whether created and
received by human beings or by machines and measuring instruments.
Noise
generally radiates in all directions, but can bend around and over walls and
buildings and can reflect back from solid surfaces.
Significantly careful positioning of noisy plant and equipment can be very
effective in reducing noise levels.
Occupational Noise
It
is well established that prolonged exposure to high noise levels can result in
permanent and irreversible damage to hearing. It is also recognized that the
only effective preventative measure is to control noise exposure before hearing
loss occurs.
Noise
induced or occupational deafness involves regular exposure to noise over a long
period with gradually acquired sensory-neural hearing loss – damage to the inner
ear and nerve pathways to the brain
Acoustic
trauma involves exposure to a very high noise level over a short period such as
an explosion perforating the eardrum
40
out of every 100 workers who have worked all their lives at high noise levels
(>90db9A) will at the age of 65 years find it difficult to hear other people
talking
This type of deafness is INCURABLE
This type of deafness can be PREVENTED
Links to
other sources of
information on occupational noise and health:
Regulations and Standards
The Safety, Health and
Welfare at Work (General Application) Regulations 2007 (S.I.
No 299 of 2007) revoke and replace the Safety, Health and Welfare at
Work (Control of Noise at Work) Regulations 2006 (S.I. No. 371 of 2006), save
that paragraph (3) of Regulation 11 of those Regulations, relating to the
entertainment sector, remains in effect until 14 February 2008. Part 5 Chapter 1
of the 2007 Regulations specifically addresses Control of Noise at Work. These
Regulations cover Directive 2003/10/EC of the European Parliament on the minimum
health and safety requirements regarding the exposure of employees to the risks
arising from physical agents (noise).
The regulations apply to all
workers and workplaces except crew members in sea or air transport. They are
aimed at protecting workers from the potential risk to their hearing caused by
exposure to high noise levels or to high noise levels over a long period of time
and therefore are aimed at preventing hearing loss and deafness.
The regulations require that the employer must
ensure that:
-
Noise experienced at work shall be assessed
and, when necessary, measured. Formal records of any assessments must be
kept in the format set down in the regulations
-
The records must be kept for at least 3 years
and made available to the employees (or their representatives) and
inspectors from the HSA.
-
Every employer shall reduce the risks
resulting from exposure to noise in the workplace to the lowest level
reasonably practicable, taking account of technical progress and the
availability of measures to control the noise in particular, at source.
-
Where the exposure to noise is likely to
exceed 80db(A), the employer shall supply sufficient numbers of suitable and
adequate personal ear protectors to the employees, following consultation
with the workers concerned regarding suitability and adequacy of the models
of hearing protection chosen.
-
Where it is not reasonably practicable to
reduce the daily personal noise exposure of a worker below 80dB (A), the
employer shall make hearing checks available to the worker.
-
Penalties be imposed for a breach of the
regulations
-
Health Surveillance must be provided to all
employees, if exposure to noise exceeds, 80dB (A)
As regards
standards, the Regulations require an employer to take
specific action at certain action values. These are the daily noise exposure
level or the peak sound pressure level which, if exceeded, for an employee,
action will need to be taken to reduce the risk. These relate to:
The values involved are:
lower exposure action values:
upper exposure action values:
The daily noise exposure or a peak sound pressure level must not
be exceeded for an employee in the workplace. When an employer is determining
the exposure limit value they must take account of the attenuation provided by
individual hearing protectors which are worn by the employees.
The peak sound pressure is the maximum value of the ‘C’ frequency
weighted instantaneous noise pressure. This can be short bursts of noise energy
at any given time.
Sound pressure (p) is the average variation in
atmospheric pressure caused by the sound. The pressure is
continuously varying between positive and negative values, so the average
variation is measured by its root mean square.
The weekly noise exposure level is the time
weighted average of the daily noise exposure levels for a normal week of a five
eight hour working days. This may be used by employer to determine the noise
exposure to employees if the daily noise exposure varies from one working day to
the next. An employer can use weekly noise exposure level, when there is a
constant variation in the daily noise exposure from one working day to the next
for the purposes of applying the exposure limit values and the exposure action
values, to assess the levels of noise to which his or her employees are exposed,
provided that;
-
The weekly noise exposure level as shown by
adequate monitoring does not exceed the exposure limit value of 87db (A),
and
-
Appropriate measures are taken in order to
reduce the risk associated with these activities to a minimum.
When the level is between 80dB (A) and 85dB (A);
the employer must (in addition to reducing noise levels by general action)
inform each potentially affected worker and their representatives of the
following:
-
the results of the measurements taken of the
noise and the possible risk to their hearing
-
Results of preventative audiometric testing
-
what measures are being introduced to reduce
the noise levels in the workplace
-
the advisability of wearing hearing
protection that’s individually fitted and where and how to obtain it
-
hearing checks that are available
-
provide any necessary information and where
relevant training
When the level is above 85dB (A) the employer
must:
-
Identify the reasons for the excess noise and
put in place a programme to reduce it. This could be either of a technical
nature or of organisation of work or both.
-
Provide the services of a registered medical
practitioner to carry out hearing checks and audiometric testing.
-
put up clearly visible and legible signs
indicating that the noise level in the area is likely to exceed 85dB (A), in
accordance with the Safety, Health and Welfare at Work (General Application)
Regulations 2007 -Part 7 Chapter 1 (S.I.
No 299 of 2007).
Workers and their representatives must be
informed:
-
that the noise level is likely to exceed 85
dBA and of the potential risk of damage to hearing
-
about the measurements taken of the noise
levels and an explanation of the significance of the results
-
about what is being done to reduce the noise
levels
An employer is required to reduce the level of
noise exposure, or any noise in the workplace to the lowest level reasonably
practicable. This may be done by:
-
reducing the noise at source, for example by
enclosing the noise source, relocating noisy machines, by screening affected
workers or by providing quiet work areas separated from the noisy area.
-
Other methods of reducing the exposure to
noise may include reducing the number of employees working in a noisy area,
or reducing the length of time they spend in the noisy area or using quieter
work methods or processes.
For more information on the specific requirements
of the Regulations visit the HSA -
FAQs on Noise at Work
For information on UK Noise Regulations -
HSE website
US Noise Regulations -
Noise Regulations
(OSHA Technical Manual)
Canadian
exposure levels
Australian noise standards
Hearing Protection
Ear
Muffs Do & Don’ts
-
The hearing
protection should be worn 100% of the time in noisy environments so as to
offer full protective effect
-
Clean the outside of the hearing protector regularly with soap and lukewarm
water (Do Not Immerse In Water)
-
Do not store the hearing protector in temperatures above +55oC.
-
The hearing protector and, in particular, the ear cushions, may be damaged
over a period of time and should be checked regularly to see if there are any
cracks or damage
-
Recommended replacement interval for foam pads/ear cushions: at least twice a
year in order to ensure constant attenuation, hygiene and comfort levels
Ear Plugs
Do & Don’ts
-
Roll the plug
between your fingers and insert while pulling the outer ear upwards and
backwards to straighten the ear canal
-
Let the plug
expand in the ear for approximately 30 seconds
-
Check the plug
attenuates noise well, without any leakage
-
Wear the plug,
preferable with the cord behind the neck
-
The earplug
should be worn at all times in noisy surrounds
-
The plug should
be stored before and between usage in a way that protects them from dirt,
grease, etc.
What is the best ear defender?
-
The one most
comfortable for the individual which offers the correct attenuation for the
level of risk
-
The best ear
defender is a cap with a very effective seal
-
All ear
defenders should be CE marked, type approved against EN352 and accompanied by
attenuation data
When
wearing hearing protectors:
-
100% Wear Time
- Provides predicted protective effect.
-
99% Wear Time -
5 minutes carelessness per day reduces the protective effect dramatically
-
90% Wear Time -
You can no longer be sure of effective protection
Links to information sources on hearing protection:
Noise Control
It is significantly less expensive (unit cost per decibel reduction) to make
noise-generating processes quieter than to make a barrier to screen the noise.
Noise levels can be lowered by eliminating or reducing
the noise at source with the use of noise-control
enclosures, absorbers, silencers and baffles and by the use
of personal protective equipment, such as earmuffs. Where
technical methods are insufficient, noise exposure may be
reduced by use of hearing protection and by administrative
controls -- such as limiting the time spent in noisy
environment and scheduling noisy operations outside normal
shifts or at distant locations.
Essential elements of environmental noise control
programmes are education and training of the workers to
minimise noise generation on a site.
When aiming to reduce the effects of environmental noise on people, it is
important to consider the:
Useful information links on noise control:
Noise Measurement
Measuring noise levels and workers' noise exposures is a critical part of any
workplace hearing conservation and noise control program. It enables
identification of work locations where there are noise problems, employees who
may be affected, and where additional noise measurements need to be made.
A noise assessment may be simple or quite complex, depending on the type of
workplace, the number of workers and the information already available
regarding noise exposure levels.
The general aim of a noise assessment is to:
- Identify all persons likely to be exposed to excessive noise;
- Obtain information on noise sources and associated work
practices to help decide what measures should be
taken to reduce noise levels;
- Check the effectiveness of measures taken to
reduce noise exposure or the risks from noise exposure;
- Assist in determining appropriate personal hearing protectors for persons
exposed to risks from excessive noise and define hearing protection areas at work.
Two different instruments are used to measure
noise exposures: the sound level meter and the dosimeter. A sound level meter is
a device that measures the intensity of sound at a given moment. To estimate
employee noise exposures with a sound level meter it is necessary to take
several measurements at different locations within the workplace.
estimates of individual exposure levels can be developed. This measurement
method is generally referred to as "area" noise monitoring.
The integrating
sound level meter (ISLM) is similar, the major difference is that an ISLM
does not provide personal exposures because it is hand-held like the SLM, and
not worn. The ISLM determines equivalent sound levels at a particular location.
It yields a single reading of a given noise, even if the actual sound level of
the noise changes continually. It uses a pre-programmed exchange rate, with a
time constant that is equivalent to the SLOW setting on the SLM.
A dosimeter is like a sound level meter except
that it stores sound level measurements and integrates these measurements over
time, providing an average noise exposure reading for a given period of time,
such as an 8-hour workday. With a dosimeter, a microphone is attached to the
employee's clothing and the exposure measurement is simply read at the end of
the desired time period. A reader may be used to read-out the dosimeter's
measurements. Since the dosimeter is worn by the employee, it measures noise
levels in those locations in which the employee travels.
A sound level meter can also be positioned
within the immediate vicinity of the exposed worker to obtain an individual
exposure estimate. Such procedures are generally referred to as "personal" noise
monitoring.
Area monitoring can be used to estimate noise
exposure when the noise levels are relatively constant and employees are not
mobile. In workplaces where employees move about in different areas or where the
noise intensity tends to fluctuate over time, noise exposure is generally more
accurately estimated by the personal monitoring approach.
Meters should be checked with an acoustic calibrator
immediately before and after measurements are taken. A full
calibration of acoustic measuring systems should be performed ideally annually.
In addition noise exposure calculators
can help you work out your daily noise exposure, weekly noise exposures, and
estimate the performance of hearing protection, the UK HSE provide some
useful calculators.
A typical Noise Survey Report could include the
following:
-
List of jobs where noise over exposures are
occurring
-
List of workers involved and training
required
-
Locations where noise control signs are
required
-
Details on measurement taken including
workplace conditions and any unusual prevailing conditions.
For more information on measuring noise:
Ototoxins
Exposure to certain chemical substances may result in hearing
loss. These substances are called ototoxins. They may damage the cochlea in
the inner ear and/or the auditory neurological pathways. Hearing damage is
more likely if exposure is to a combination of substances or to a
combination of the substance and noise. Ototoxins can be workplace chemicals
and/or medication. This is an area where much research is still ongoing,
however workplace chemicals which are usually considered for inclusion
include some solvents and heavy metals.
Links to further information at:
Consultnet Noise Consultancy
Services
At Consultnet we offer a range of occupational noise consultancy
services including:
-
Workplace noise assessments
-
Recommendations for noise conservation
programmes
-
Solutions for noise control
-
Provision of employee information and
training
Our consultants have over
twenty years experience in noise monitoring, interpret ting regulations and
developing noise control solutions. As a small company
we are flexible, can make decisions quickly and develop practical cost effective
solution for our clients.
Consultnet Environmental Noise Monitoring Services
Links to Information Sources on
Occupational Noise:
|
Noise at Work