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What Have You Heard About Noise?

Published: 01st Apr 2012


The European Union’s Green Paper on Future Noise Policy estimated that 80 million people throughout Europe suffer from unacceptable noise levels that cause sleep disturbance, annoyance and adverse health effects. The Green Paper further estimated that around 40% of the European population lives in areas where environmental noise causes serious annoyance during the daytime.

Various other estimates of the scale of the problem have been produced since 1996, but all generally agree that very large numbers of people are seriously affected by noise.

The European Environment Agency (EEA) has published many EIONET noise newsletters since May 1999 to raise public awareness of increasing noise problems throughout Europe, and the progress being made to combat this.

In addition to many national standards and regulations throughout Europe, there are a number of European directives designed to limit industrial noise, vehicle pass by and indoor and outdoor machinery noise emissions. The European Commission’s proposal for a directive on the assessment and management of environmental noise considers the control of noise emission at sensitive receivers, rather than just in terms of noise emission limits imposed at source.

Around the world, there are many hundreds of millions of people exposed to levels of industrial and environmental noise that would be considered as unacceptable in Europe. The World Health Organization (WHO) Guidelines for Community Noise document set out stringent guideline values for industrial and community noise in specific environments.

Most developed nations throughout the world have existing or planned regulations for the limitation and control of community noise, and many less developed nations are also taking an increasing interest in this area.

Because of this increasing emphasis on environmental and community noise as a problem affecting vast numbers of people, all commercial and industrial enterprises need to devote an increasing proportion of their overall environmental resources to noise assessment and noise control.

The current WHO guidelines define the goal of noise management as “to maintain low noise exposures such that human health and wellbeing are protected,” with “specific objectives to develop criteria for the maximum safe exposure levels and to promote noise assessment and control as part of environmental health programmes.”

The WHO guidelines also set out the following three main principles:

• The precautionary principle

• The polluter pays principle

• The prevention principle

The net effect of these three principles is that noise control action is considered to be justified wherever there is any reasonable possibility that human health and wellbeing will be damaged, irrespective of whether there is any scientific proof available at the present time (the precautionary principle); that all costs should be met by those responsible for the noise source (the polluter pays principle). There is a clear implication that the WHO considers that the existing balance between the costs and benefits of noise control needs to be shifted towards increased protection of the public, almost regardless of any costs to industry and commerce.

The effects of noise and vibration in general terms have been researched over some considerable time and issues such as tinnitus and ‘white finger’ recognised, and statutory regulations make the HSE enforcements a simple mechanism. The present ‘guidance’, however, is limited to The Control of Noise at Work Regulations, 2005. These state: “Exposure to harmful noise levels at work can cause irreversible hearing damage. This damage involves the loss of hearing ability over and above that which normally occurs as we grow older and may be compounded by Tinnitus (troublesome noises in the ear) and other effects such as disturbance, interference with communications and associated stress.

“Damage is usually gradual due to prolonged exposure; however, instantaneous damage may occur if peak sound wave pressures are too great.

“Noise exposure in the workplace is controlled through the Control of Noise at Work Regulations (2005) which supplements the general duties set out in the Health and Safety at Work Act (1974). They have been formulated to protect against risks arising from noise exposure and define specific obligations to prevent employees suffering hearing damage at work.”

The cornerstone of the Control of Noise at Work Regulations (2005) is the requirement to assess the noise exposure of employees, and identifies the following action values:

• Lower Exposure Action Value - Daily personal noise exposure of 80 dB(A) and a peak sound pressure level of 135 dB(C)

• Upper Exposure Action Value - Daily personal noise exposure of 85 dB(A) and a peak sound pressure level of 137 dB(C)

The daily personal noise exposure (L EP, d ) is the noise to which the employee is exposed during the working shift, normalised over an eight hour period. Where there are significant variations in noise exposures from day to day, it may be more appropriate to determine weekly exposure levels which can be compared to the Action values.

The Control of Noise at Work Regulations (2005) further states: “Use of weekly exposure might be appropriate in situations where noise exposure varies markedly from day to day, e.g. where people use noisy power tools on one day in the week but not on others. It is only likely to be appropriate where daily noise exposure on one or two working days in a week is at least 5 dB higher than the other days, or the working week comprises three or fewer days of exposure.”

Other aspects of the regulations relate to:

• The general duty to reduce risk

• The control of noise when employees are likely to be exposed above the Upper Exposure Action value, so far as is reasonably practicable

• Ear protection zones

• The provision of ear protection

• Use and maintenance of ear protection

• Provision of information, instruction and training

• Audiometric testing Noise emission standards have proven to be inadequate.

Much of the progress towards solving the noise pollution problem has come from advanced technology, which in turn has come about mainly as a result of governmental regulations (e.g. OECD-ECMT). So far, however, the introduction of noise emission standards for vehicles has had limited impact on exposure to transportation noise, especially from aircraft and road traffic noise.

In part, this is because changes in human behaviour (of polluters, planners and the general public) have tended to offset some of the gains made. For example, mitigation efforts such as developing quieter vehicles, moving people to less noise-exposed areas, improving traffic systems and direct noise abatement and control (e.g. sound insulation or barriers), have been counteracted by increases in the number of roads and highways built, by the number of traffic movements, and by higher driving speeds and the number of kilometres driven.

Traffic planning policies may diminish the number of people exposed to the very high community noise levels (>70 dB LAeq), but the number exposed to moderately high levels (55-65 dB LAeq) continues to increase in industrialised countries. In developing countries, exposure to excessive sound pressure levels (>85 dB LAeq), not only from occupational noise but also from urban, environmental noise, is the major avoidable cause of permanent hearing impairment. Such sound pressure levels can also be reached by leisure activities.

The hidden danger

The Noise at Work 2005 regulations fall well short of subjectively addressing low frequency noise exposure below or near the hearing threshold. The low frequency ‘infrasound’ (less than 20 Hz) level exposure analysis considers changes in heart rate, peripheral vascular blood flow, skin temperature, cortisol levels and vestibular functions - which through research, have indicated could have been triggered by the lower parts of the frequency spectrum.

Studies have further established that fatigue and tiredness during the progressive working day and after work increased with exposure and dominance of Low Frequency Noise (LFN). These assessments also described complaints following exposure to LFN: general fatigue, feeling of apathy, loss of concentration, somnolence and depression. Subjective data analysis found that workers complained about increased irritability, headaches, periodic vertigo attacks, increased non-temperature affected perspiration levels and tiredness, sleep disturbances, pains in the region of the heart and difficulty in breathing.

The hidden risk

This progressive risk to the working environment and personnel is far too important to simply ignore and brush aside. All the indications are there: workers in all professions and trades generally and specifically exposed to low frequency noise are both at risk to themselves and thereby affected or, are equally presenting a potential danger in creating an unsafe work activity and a multitude of associated safety issues.

These considerations, which presently appear unidentified in any risk assessments, as far as I am aware so far, are ones which I have personally researched. Employers and responsible bodies cannot hide away from this risk under the present noise at work regulations: should any litigation emerge, and subsequently be proved as being directly linked to the subjective low frequency noise issues raised in this document, it is quite likely the flood gates would open.

Are you at risk? Think about it!

To cite an example: Consider the environmental and vehicle generated low frequency emissions in the case of an HGV lorry driver. Firstly, the low frequency elements of noise and vibration exposure are generally not addressed under CE marking legislation for vehicles. Figures provided are only published as down to, say, 31.5 Hz (very rare, at best). Other manufacturers’ noise level statements are only ‘identified’ from the 125 Hz frequency ranges.

While these ranges are audible to the human ear and covered under vehicle design mitigation strategy, the manufacturer still fails to address these low frequency noise exposure elements. This lack of information by association exposes the end user to the hidden risks, symptoms as previously defined, and directly associated with these low frequency ‘hidden’ noise elements. They are therefore instrumental in creating an environment to add to the road/stress factors encountered in the driver’s daily tasks. Surely this situation is one of the more dynamic, ‘dangerous’ occupations to consider, again as drawn subjectively from the above described complaints resultant from low frequency exposure levels in the workplace.

To demonstrate the scenario, we have probably all been aware in some form of an HGV standing adjacent to or passing by us, either in traffic and perhaps also in the home, and felt the sound energy both aurally and mechanically, where also the noise and vibration causes windows and other items to rattle, or worse. The driver is exposed to this throughout his working day. Manufacturers are generally aware of these issues and will ‘mitigate’ for human audibility in their designs. I am presently unaware of the issues of noise control of low frequency from manufacturers publishing the results of any testing for the ‘inaudible’ noise considerations, which are obviously proven to be there.

Tinnitus is not a disease, but an aural condition characterised by noises in your head that can be heard in the absence of ambient sounds. The noises seem to occur in one or both ears and can sound like ringing, buzzing, whistling, hissing and often seem louder when the environmental noise is low, typically heard at night or when in very quiet places. In some cases tinnitus will be modulated by your pulse; this is called pulsatile tinnitus and is likely to be related to blood circulation disorders. Most of us will have experienced tinnitus at some time - usually a brief low-level tone burst that is not intrusive or anything to be concerned about. More severe and long term tinnitus is usually triggered by stress, but by far the most common cause is exposure to loud noise: typically, rock concerts, night clubs or industrial noise and it is very dangerous.

Again, we must address the full spectral frequency analysis of the offending noise to fully comprehend the individual or specific noise relationship to the receptor, not just as the cause of tinnitus, but as the beginning of other permanent long, term noise induced hearing loss. This is now being considered as only one facet of the holistic noise intrusion. The RNID has been running a campaign called Don’t Lose the Music to increase awareness of people attending entertainment venues with high volume levels. There is no ultimate cure for tinnitus, but with therapy, noise enhancements, masking and the use of personal custom designed earplugs it can be managed to a tolerable level, or below your hearing threshold, which will be like a cure - but obviously it can return, especially if noise or stress induced conditions are ongoing.

It is impossible to state which of the solutions is best. It depends on how severe your condition is, what triggers it and when it occurs - and the individual’s hearing thresholds and template. The fact is that tinnitus is now a universally recognised condition, so this factual status adds significant weight to the fact that low frequency noise must be considered as being directly injurious, could potentially cause long term illnesses and perhaps in a number of cases, be untreatable.

Previous research

Mohr et al carried out systematic investigations with different types of LFN exposures of very high level noise. The following subjective sensations were described:

• 124 dB / 10 Hz - 400 Hz broad band noise for two minutes, one of five persons without ear protection??

• 114 dB - 133 dB / 35 Hz - 140 Hz octave band noise for two minutes, one of five persons without ear protection??

• 144 dB / 4 Hz - 4 kHz broadband noise for one minute The resulting comments were?? awareness of restricted respiratory action; sensation of moderate chest wall vibration; hypo-pharyngeal fullness; perceptible visual field vibration; prolonged post-exposure fatigue caused by 143 dB - 145 dB / 10 Hz - 60 Hz narrow band noise; abdominal wall vibration due to 150 dB - 154 dB / 10 Hz - 20 Hz narrow band noise for two minutes; and nostril vibration during test 10 (5 Hz - 10 Hz)?.

The highest pure tone exposures were used to check tolerance thresholds (140 dB - 154 dB / 40 Hz - 100 Hz, three subjects). All three subjects wore ear protection. It was decided to stop the exposure, because the following alarming responses occurred:

• Transient headache (one subject only) at 50 Hz / 153 dB

• Coughing, sub-sternal pressure, choking respiration, salivation, pain on swallowing, hypo-pharyngeal discomfort, giddiness, testicular aching (one person only) at 153 dB / 60 Hz and 150 dB / 73 Hz

• Mild nausea, giddiness, subcostal discomfort, cutaneous flushing, tingling at 153 dB / 100 Hz

• All study participants suffered from evident post-exposure fatigue

The above facts are cited to provide an awareness of the seriousness of noise and vibration exposure to humans. Further research on the effects of noise and vibration will almost certainly prove there is more direct danger to the human internal organs and infrastructure. The figures are from worst case illustrations, but the underlying LFN issues are therefore proportionally applied and require acknowledgement.

Human physiology

In simple terms, human physiology is the study of the body and its functions in each of the different systems in any living body. Physiology focuses principally at the level of organs and systems. As already indicated above, these effects can be emergent due to exposure below the hearing threshold, because these facts presuppose a conscious perception of the LFN. The findings also seem to support changes in blood pressure, respiration rate, EEG patterns and heart rate caused by exposure to LFN, both perceptible and imperceptible.

The research and current information reviewed in this tract is mainly based on laboratory studies. Only a few field studies were found. A comprehensively critical view of methodological issues concerning these findings is needed. The following comprehensive but not exhaustive topics must be further explored as essential in the consideration of the effects of low frequency noise holistic exposure to the human body for later studies.

Investigation of effects frequency spectra measurement and statistical control of confounding factors

•Consideration of individual differences, taking into account various risk groups

•Investigation of LFN contribution, ‘through/whole body’ direct intrusion and effect to the human organs development of mitigation methods for LFN attenuation

•The measurement of the individual hearing threshold and the vibro-tactile threshold for airborne LFN

The level of the airborne noise and the body vibration caused by this airborne noise - or by other sources - ought to be considered simultaneously. Appropriate methods for laboratory and field studies were described by Takahshi et al (1999 and 2001) and Smith (2002). Combined effects of LFN and body vibration should be taken into account. There is some evidence of mutual effects of both factors at least concerning the thresholds of hearing and vibro-tactile sensation4 and the influence of vibration on the equal loudness level contours.

Guilty as charged

Noise has always been a poor relation in the industrial and commercial worlds - FACT. It is ignored in the hope that it will go away, stop being a nuisance, or is met with attitudes such as ‘Oh yes, we’ll get round to it in the next financial year’.

I have heard all of the excuses not to address the issue. ‘If it doesn’t add to the balance sheet, we won’t do anything’. Well, the regulatory focus is being aimed at putting that right. It may take some time, but eventually employers will have to conform, like it or not. It is a criminal offence to not ensure the safety and wellbeing of workers. In the roles and practices they carry out, their associated tasks and duties, they need protection from noise associated ills, whether that be tinnitus, white finger or low frequency whole body exposure.

The penalties for incidents and events are high, for both companies and for the individually responsible people and risk assessment teams. It is your duty to make it safe. The cost of mitigation is not the true penalty; it is the individual and their families that it affects - that is the real burden.

What can be done?

The present regulations and mandatory Noise at Work 2005 guidance simply does not achieve anywhere near a sufficient or satisfactory solution. For example, the earplug, the hearing defenders provided by the employer, correctly used and applied, give anywhere between 9% - 25% performance effectiveness. At best they offer a partial protection only. This in no way addresses any low frequency issues discussed within this article.

The best solution is, wherever practical, to reduce the noise emissions at source and thereby provide a safe working environment for all affected receptors. Is your company at risk? Are you guilty as charged?

Published: 01st Apr 2012 in Health and Safety International

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