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The association between "noise and noise induced hearing loss" can trace its origins back to the early 1600's to metal workers (Blacksmiths), pounding metals into various objects for everyday use. Miners often suffered "noise induced hearing loss" due to blasting over prolonged periods of time, or as a result of blast deafness instant permanent hearing loss due to extreme noise levels above 140dB. More recent times 1900's, servicemen in the first-second world wars through exposure to artillery rounds and explosions, (Rabinowitz, 2000).
As the advent of new processes such as textiles; engineering; manufacturing and technological advances have revolutionised the workplace, noise levels within these environments has also increased. However our initial understanding of the impact of increased noise pollution remained relatively unknown and sometimes oblivious by employers as to the impact upon employees? More recent times, the effect of noise through our environment in areas such as road traffic levels, the construction of buildings in channelling sound by increasing the frequency (pitch), of the sound wave as well as the cycle (wavelength-amplitude). Further factors to consider can be related to social factors, more and more people are using portable music devices not only in social application, but also within there working environment exposing them to even further prolonged periods of noise interaction, (Stansfeld, Matheson, 2003).
The effects of noise in the workplace pose significant risks to various groups of employees; workers and stakeholders during their activities. (Lusk, et al,. 2002) highlights the need to create a "health risk profile" in order to establish positive identification as to who is directly-indirectly at risk. "Noise induced hearing loss" can be attributed to workplace occupational-environmental situations, which are normally caused by prolonged exposure to high noise levels. Damage to the cilia (hair cells) within the cochlea, leading to temporary-permanent "threshold shift" caused at certain frequencies (3,000 - 6,000 Hz) which worsens with continued unchecked exposure.
The use of "epidemiological studies" are often not very effective when dealing with noise induced hearing loss studies, the lack of available "longitudinal dose-response data" combined with audiometric testing (over prolonged periods of time) makes it difficult to determine whether practical methods of hearing protection are indeed effective in the long term. Recent data suggests that over one million people are at risk as a result of exposure to noise in the workplace, which may cause serious risk to their hearing. Further evidence shows that seventeen thousand people suffer some form of auditory related condition(s) due to excessive noise levels at work, (The Health and Safety Executive, 2012).
Appendix 1â€¦ Managing Noise Risks Process Flow Chart.
Appendix 2â€¦ Noise Risk Assessment Process.
It is the primary aim of this paper to carry out a critical evaluation of an Occupational Illness-condition: - Noise induced hearing loss in the workplace, evaluating factors which influence current identification, control and prevention techniques. Using peer reviewed papers, incorporating their merits, limitations and the effectiveness of strategies employed in current noise control methodology.
(The Control of Noise at Work Regulations, 2005) requires employers to identify sources of noise in the workplace to which their employees are exposed to during their normal working hours. Employers are required to undertake measures to ensure that exposure limits do not exceed legal limits, employ robust managements systems for training, instruction, information where identified, provide hearing protection and health surveillance regimes when indicated. Initial first steps would be to undertake a risk assessment process (RA) by identifying the areas/individuals at risk, to take action to reduce-eliminate any possible adverse exposure levels where reasonable practicable.
Dose-response associated symptoms of noise exposure, Non-auditory Effects.
Long or even short term exposure to excessive noise levels can have a profound impact on employee's health and can manifest its self in physical disturbances outside the normal scope-association of traditional hearing problems. (Lusk, et al., 2002) highlights very high levels of noise have been found to cause muscular tension, tightening of blood vessels, raised heart rate and server effects on the digestive system, culminating in both physiological-psychological disorders. Conversely low level noise exposure over prolonged periods have shown increased levels of irritability in individuals, issues of sleep deprivation culminating in added symptoms of stress disorder. (Smith, 2003) also outlines a correlation between noise levels and accident causation. Individuals are at higher risk of distraction and lowered concentration when exposed to noise interferences, leading to lowered levels of perceived cognitive awareness within their working environment.
Temporary noise-induced threshold shift, Auditory-Acute Effects.
The human ear hears noise from 0-15 decibels (dB), when an individual is exposed to high levels of noise the threshold at which that individual hears that sound may temporarily shifts by up to 20 (dB). However the individual gradually recovers taking two-three days to recover completely. Further conditions associated with exposure to noise include temporary tinnitus, e.g. a ringing, buzzing, whining noise within the ear caused by over stimulation of the cilia (hair cells). However continual-constant exposure levels are a precursor to possible long-term hearing issues if not addressed and can lead to further progressive symptoms.
How this occurs, the human ear is made up of the outer ear; middle; inner ear, through which sound enters and resounds on a tympanic membrane, like a drum. Vibrations move three small bones; the malleus, incus and stapes, which cause fluid in the cochlea to move tiny cilia (hair cells). As the cilia move they send electrical signals to the brain, which are then interpreted as sound. (Kurmis, Apps, 2007).
Noise-induced threshold shift, Auditory-Chronic Effects.
(Konig, Schaette, 2006), highlight that the symptoms of permanent chronic-tinnitus are very much the same as temporary tinnitus, however indications would suggest that noise-induced hearing loss can be prevalent across a wider range of hearing thresholds.
Occupational hearing loss (chronic-tinnitus) usually occurs when individuals are exposed to noise levels up to and above 3-6 kHz range over prolonged periods of time.
Noise Control Measures.
Controlling the levels of noise exposure in the workplace concerns the total dose of noise that affects individuals or groups of individuals within sections of areas, or as a total within the workplace. In most work situations the noise exposure levels will fluctuate considerably throughout the day.
The total exposure dose is determined by averaging the level of noise over an 8 hour period for daily exposure and 40 hours for weekly exposure levels to give a single level for that period of time. Known as the daily (LEPd and the weekly LEPw), (Konig, Schaette, 2006)
Example: - Noise levels equivalent to 85 dB(A) for 8 hours.
88 decibels for 4 hrs, e.g. heavy traffic:
91 decibels for 2 hrs, e.g. a circular saw:
94 decibels for 1 hr, e.g. an air compressor:
97 decibels for 30 mins, e.g. a metal grinder:
100 decibels for 15 mins, e.g. a chain saw.
Exposure Limits and Action Values.
The aim is to prevent damage to hearing. At all levels employers have a duty to reduce noise so far as is reasonably practicable, (The Control of Noise at Work Regulations 2005) specifics lower and upper exposure action values.
Lower Exposure Action Value.
"This is a daily or weekly personal noise exposure of 80 dB(A)" and a peak sound pressure of 135 dB(C).
At this level employers should provide information, instruction and training on:
The nature of the risks from exposure to the noise levels.
What steps the organisation (technical measures) has taken to reduce the noise levels within their section or area(s).
Full disclosure of the limit values highlighted both upper and lower exposure action values.
The findings of any risk assessment process including any measurements taken, with a full explanation of how and where.
Training on why and how to detect, report signs of hearing problems.
Instruction on safe working practices to minimise exposure to noise
The provision of PPE, its use suitability, purpose for use, fault, damage inspection, replacement when worn.
Whether a risk assessment has indicated the need or entitlement to health surveillance regimes.
Who has carried out the exposure assessments, competency, and qualifications?
Upper Exposure Action Value.
"This is a daily or weekly personal noise exposure of 85 dB(A)" and peak sound pressure of 137 dB(C). At this level employers should so far as is reasonably practicable, reduce exposure other than providing hearing protection, e.g. by engineering control methods.
Exposure Limit Value.
"A daily or weekly personal noise exposure of 87 db(A)" and peak sound pressure of 140 dB(C). At this level instant hearing damage may occur. An employer should reduce the level, identify WHY the level was reached and ensure it is not reached again.
Noise Control & Prevention.
Like other forms of pollution, noise can be controlled by attention to the following factors: The Source, The Path and the Person.
Figure 1. Noise Source, Path and Persons Exposed
Direct noise Refelcted noise
Structure borne noise
An effective measure for controlling noise at source would include a technical review of the design of the unit. Changing selected parts of the item (e.g. nylon gears rather than metal) would help suppress the amount of structure borne noise. Additional added features could also include dampening methods, adding materials to reduce-suppress vibration. Further measures could include, heavy metal based paints used on machinery housings or general ventilations systems.
Using isolation techniques to further prevent noise transmission structurally borne through the building, (floor-walls), mounting machinery on anti-vibration feet). This is particularly important where the detected noise is in the low frequency ranges, which are most easily transmitted through structures.
Absorption sounds in an area; workroom can be absorbed by means of acoustic absorbent panels on walls or suspended from the ceiling. In large areas-workrooms, particularly where many noise sources are present, much of the noise will be reflected from the walls and ceiling. Absorbing this energy can significantly reduce the levels of noise to which employees are exposed. Silencer attachments are also an effective means of reducing noise. Fitted to the inlet or exhaust (or both) of a moving air or gas stream emitted from the machine. The increased volume of the silencer decreases the speed of the air at the exhaust.
Screens and barriers are other forms of noise suppression, placing an obstacle between the noise source, (machine, and employees) can reduce direct noise. However this method has limitations and may prove ineffectual at low level frequencies radiated noise transmission as well as reflected noise paths.
(The Health and Safety at Work etc Act 1974) Section 6, outlines that "manufactures, suppliers of machinery must provide equipment intended for use is safe for use at work". (The Supply of Machinery (Safety) Regulations 2008), outline.
The identification of all the hazards-including misuse to their machinery
Design-consult, taking into accounts the assessment process
That they meet the essential health and safety requirements (EHSRs) in the regulations.
The Provision and Use or Work Equipment Regulations 1998 (PUWER) maintain.
Equipment is suitable for the intended use.
Safe for its use.
It's maintained in a safe working condition.
Only used by people with adequate information, training, instruction.
That suitable safety measures; protective devices, markings, warning signs are available.
When identified by a risk assessment, an employer where possible must eliminate or reduce so far as is reasonable practicable, exposure to noise sources within the working environment. (E.g. changing the working method of the equipment, dampening, absorption, silencing, etc.), or by the purchase of quieter equipment. However, where safe place strategies are not possible, safe person strategies should be implemented, (The Control of Noise at Work Regulations 2005).
Distance, positioning the employee away from the noise source will reduce the noise dose received.
Time exposed, halving the time exposure will reduce the noise dose by 3dB.
Training and information about the noise exposure and the associated risks to hearing.
Where and how to obtain hearing protection.
How to report defects in hearing protection.
What the employee's duties are under (The Control of Noise at Work Regulations 2005).
What the employee should do to minimise the risk, such as the proper way to use hearing protection and other noise equipment, how to look after them, and where to use hearing protection.
Appendix 1 Managing Noise Risk Process Flow Chart
Assess the Area-Risks.
Identify noise exposure hazards.
Evaluate the likely exposure to the noise.
Identify measures required to eliminate or reduce risks, control exposures and protect employees. E.g. mechanical/physical means.
Make a detailed record of what you will do in the action plan. Involve employees at all stages of the process.
Employees/stakeholder information and training.
Consult workers/union and safety representatives, allow their participation in the process.
Give employee information, instruction and training about the risks, control measures, hearing protection and safe working practices.
Protect your Employees
Eliminate or control noise risks.
Eliminate or reduce risks using good practice and known controls combined with management solutions.
For the higher-risk cases, plan and put into place technical and organisational noise-control strategies.
Make sure the legal limits on noise exposure are not exceeded.
Provide adequate hearing protection
Protect your employees with hearing protection when identified, suitable and appropriate for the task.
Make its use mandatory for the high-risk causes (keep working on technical and organisational control measures)
Manage the use of hearing protection with zones, instructions and supervision mandatory when identified.
Health surveillance regimes.
Provide health surveillance (hearing checks) for those at risk, audiometry/audiometric testing.
Use the results to review controls and further protect individuals.
Employees co-operate and attend for hearing checks.
Maintain and use the equipment.
Maintain any noise-control equipment and hearing protection.
Ensure that anything supplied is fully and properly use.
Employees use the controls provided and report any defects.
Employees use hearing protection where its use is mandatory.
Review what you are doing periodically.
Review as things change:
Changes in work practices.
Changes in noise exposure Levels in zones or areas.
Improved/new technological advances to reduce noise exposure risks. Employer Actions
Appendix 2 Noise Risk Assessment Process
Is there any area/task or process which could be considered noisy?