So, you have predicted that the hearing protection worn by staff in your workplace provides the correct amount of attenuation, but what happens if these devices are removed even for a short period of time whilst in a high noise environment? How does it impact the hearing protector’s effective attenuation?

If a hearing protector is not worn for 100% of the time in a noisy environment, then its effectiveness decreases rapidly. The graph below shows the reduction in effectiveness of a hearing protector that is removed for a period of time expressed as a percentage of the total time that the user is exposed to the noise. Three different hearing protectors each of varying degrees of protection are represented in the graph.

When all 3 hearing protectors are worn for 100% of the exposure time the effective attenuation is as predicted (i.e. 30dB, 20dB, and 10dB respectively for all 3 of them). However, if the 30dB rated hearing protector is worn for 98% of the exposure time (or removed for 2% of the time), then the effective attenuation drops by approximately 12dB. As an example, for a noise exposure period of 8 hours, this would imply that removing a 30dB attenuation rated hearing protector for nearly 10 minutes would give only about 18dB of hearing protection!

By comparison, the drop in effective attenuation is only 1dB to 2dB when the lowest rated hearing protector (offering 10dB protection) is removed for 2% of the time that the wearer is exposed to noise.

When all the 3 types of hearing protectors are unworn for 50% of the noise exposure time, then the effective attenuation is 3dB only for all of them.

Another surprising observation as you can see in the graph below, is that the hearing protector offering 10dB of attenuation, if worn (correctly and consistently) for 100% of the time, will provide just as much protection as both the potentially more expensive 20dB and 30dB rated hearing protectors worn for 90% of the time (for an 8 hour noise exposure period, this is equivalent to not being worn for 48 minutes).

The important lesson is…

Employees must understand the importance of wearing hearing protection before entering an area of high noise, and that when hearing protection is removed even briefly whilst in noisy environments, the effectiveness of the hearing protector can be severely reduced. This attaches great significance to selecting comfortable hearing protection (appropriately rated, of course) as the temptation to remove it is substantially reduced. Giving employees a choice of protectors also helps with wearer compliance.

Download a free guide to see what a good noise risk assessment must consist of. This guide also explains why overprotective hearing protection can be hazardous in the workplace. Click here to receive the guide.

It may not be obvious to many, but employees who regularly use headsets and earphones in workplace environments like command and control rooms, call centres, trading floors, television broadcasting studios, and offices, may be at risk of developing hearing damage from these devices. This would also apply to employees working at home wearing headsets and earphones for online meeting purposes, which has drastically increased during the pandemic and may be more common practice going forward.

Employers are just as duty bound to offer such employees protection against hearing damage in accordance with the Control of Noise at Work Regulations (2005) as they are to other noise-exposed employees in industrial environments. So how should the noise exposure of these wearers be assessed against the legislative requirements?

We are probably familiar with measuring hazardous noise in industrial situations using a sound level meter in the vicinity of the worker’s ear. When trying to adopt best practice, the aim is to locate the sound level meter at a position where the effects of body reflections are minimised. The sound field at this location is described as the ‘undisturbed field equivalent’, and therefore the measured levels here are considered as representative of the noise that the worker is exposed to. Regulatory limits are based on measuring noise this way.

Manikin

In the case of a assessing a headset or earphone, you certainly shouldn’t bring the microphone of the sound level meter against the device and use the measured result for predicting the daily personal noise exposure. The result would be invalid. Instead, it is more appropriate to use a specialist piece of equipment called a manikin.

The manikin is comprised of a simulated head with either a full torso or shoulders only, and is known as a Head and Torso Simulator (HATS). The head part incorporates an artificial ear which is a realistic flexible structure (the pinna and concha) that is made from a soft rubber material, a cylindrical ear canal, and a microphone at the end. This microphone is situated where the ear drum normally lies. The HATS is an anatomically averaged representation of the human head, pinna, concha, and ear canal and specifically designed to international standards.

Head Related Transfer Function

The headset, or earphones, should be carefully mounted on the HATS and the acoustic output of the devices are measured by the manikin’s microphone. However, it is not appropriate to use this result directly for predicting the daily noise exposure as it needs processing first. To understand why, requires a knowledge of the Head Related Transfer Function (HRTF).

The ear canal acts as a resonant tube and when sound enters and travels through it, frequencies between 2kHz and 4kHz are amplified. As a consequence, at the eardrum, the sound may be boosted by up to 15dB (depending upon the frequency spectrum of the noise) compared to the ‘undisturbed field equivalent’, position (B in figure 1).

A correction is therefore required to convert measurements at the eardrum (A in figure 1), for noise exposure prediction purposes. The correction to be applied is the HRTF, which is frequency dependent, and usually stated in intervals of 1/3^rd octave bands (see figure 1) for computational purposes. Manikin manufacturers should be able to provide the HRTF data on request.

Figure 1 – The Head Related Transfer Function (HRTF)

To obtain the sound pressure level at the ‘undisturbed field equivalent’ position, the HRTF must be subtracted from the sound pressure level measured at the eardrum position in each of the 1/3^rd octave bands, i.e. B = A – HRTF.

Each of the spectral components at position B must then be ‘A’ weighted and summed to give the overall ‘A’ weighted ‘undisturbed field equivalent’ sound pressure level. It is this result that may be used to predict the daily noise exposure of the headset wearer, and therefore compared against the regulatory limits.

Note that without applying the HRTF correction, there’s a high risk of drastically overestimating noise exposure if the sound pressure level measured result at the eardrum position is used to predict the daily noise exposure.

ISO standards

ISO 11904 – 2 specifies a test method (using a manikin) that can be used to determine the noise exposure from sound sources like headsets and earphones. This standard specifies an HRTF which is often closely matched to the manufacturer’s specified HRTF.

It is also possible to measure the noise in a real ear as produced by a headset, where a miniature or a probe microphone is inserted at the entrance of the ear canal of the headset wearer. This is often known as the Microphone in Real Ear (MIRE) technique of measurement. ISO 11904 – 1 specifies a test procedure to use for determining the noise exposure.

Each ISO method, whether using a manikin or MIRE method has its practical limitations. For example if the exposed person is using earphones that sit in the concha, or in the ear canal, then using the MIRE technique may not be practical. However, if the exposed person has to operate equipment at a fixed position, then he/she cannot be replaced by a manikin. The MIRE method may be more practical under this circumstance.

Controlling noise exposure

You may well ask, how can the noise exposure be controlled so that harm to hearing is minimised? The obvious solution would be to turn down the volume (or electronically limit) the audio to the headset or earphone but if the background noise is too intrusive, doing so may degrade speech intelligibility.

Effective ways to reduce or suppress background noise could be as simple as applying acoustic treatment to reflective surfaces such as ceilings and walls, locating noisy equipment away from those wearers affected, and introducing screening around the headset users. This should increase the signal to noise ratio and boost the ability to communicate more effectively.

Contact us to see how we can help.

We explain a strategy to adopt when measuring loud event type noises, and how to use the results to predict the contribution to your employees’ daily personal noise exposure.  A convenient table to use as a tool for the prediction is included

There might be loud, potentially harmful noises that exist in your workplace which appear in the form of events such as bursts, impulses, explosions, and impacts (e.g. from sources such as air jets, riveters, firearms, forge hammers, and nail guns). When carrying out a risk assessment, It may be desirable to assess such events separately for predicting the contribution of these types of noises to your staff’s daily personal exposure, L_EP,d.

So what measurement strategy could you adopt for these types of noise events? How can you use the results to determine the contribution to the L_EP,d in your workplace? Employers are duty bound to reduce the L_EP,d to as low as reasonably practicable to comply with the Control of Noise at Work Regulations (2005).

Sound Exposure Level

One strategy that you could adopt would be to measure a quantity known as the sound exposure level (L_AE) of the noise.  By definition, the L_AE is a measure of the acoustic energy in an event, or a given number of discrete events which would have the same amount of acoustic energy as a constant noise level lasting for 1 second. Put simply, the L_AE is mathematically equal to an averaged sound level, L_Aeq, normalised to 1 second. Most ‘professional’ sound level meters used for carrying out measurements in the workplace should be capable of measuring the L_AE.

Once the L_AE is measured for an event or series of events, and knowing the likely number of these daily events, it is possible to predict their contribution towards the L_EP,d .This prediction may be conveniently expressed in the form of the HSE ready reckoner noise exposure points. A useful table to have at hand is provided below to make this prediction relatively easy, and a worked example further below demonstrates how to use this table.

As a reminder, the regulations state that the Lower Exposure Action Value (LEAV) is equivalent to 32 HSE exposure points (L_EP,d = 80dB), and the Upper Exposure Action Value (UEAV) is equivalent to 100 HSE exposure points (L_EP,d = 85dB).

Example

Below is a time history plot of a series of impact like events generated by a carpenter hammering nails into a wood panel. The objective is to measure the L_AE of the events and use this value to predict the noise exposure points contributing to his L_EP,d. , using the table above.

A noise measurement of the 10 hammer blow events was carried out and the L_AE measured 118dB.

The carpenter estimated making 100 blows daily in total.  From the ready reckoner table above, the ratio of the number of events during the day/the number of events during the measurement equates to 100/10 = 10.  This value ‘intersects’ with an L_AE of 118dB in the table giving 70 noise exposure points which contribute towards his L_EP,d. He would only need to be subjected to an additional 30 exposure points (perhaps originating from other noise sources) to reach 100 points, and hence be exposed to the UEAV.

So providing noise containing high noise events are assessed in this manner, it is possible to predict the contribution of these noise events towards a person’s L_EP,d.

Point of note:

If you choose to predict the contribution to the L_EP,d of events using this method, then do ensure the exclusion of these events when measuring the L_AEQ of other types of noise in proximity.  Failure to do so will inevitably run the risk of overestimating the L_EP,d as you will duplicate the contributions from the events.

What do you need to consider when carrying out a competent noise risk assessments in a workplace?  Find out by clicking here to download a free guide. This guide also includes how to identify hearing protection overprotection, which may be a hazard in the workplace.

Over the last few months, concerned workers have been contacting Essel about Hand Arm Vibration syndrome (HAVS) after downloading informative content posted on our website.

A common thread amongst these calls was a description of symptoms consistent with the early stages of HAVS injuries from the regular use of powered tools. However, a disturbing trend emerged regarding their employer’s attitudes to their concerns, which has prompted writing this article.

Head in the sand?

When the employees’ symptoms were reported to management, it seemed that the complaints fell on deaf ears (no pun intended) and very little effort was expended in taking matters further, i.e it was a “just get on with it” reaction. In one case the operative had to overcome his employer’s reluctance to his requests for health surveillance, but then only because of his persistent complaints!

Despite the outcome of tests showing the early stages of HAVS, the process of managing the employee also appeared to be poor, therefore increasing the risks of an irreversible injury. The businesses seemed unaware (or undeterred) that they were on the wrong side of the law, risking prosecution and heavy fines. Employers are duty bound to protect employees with respect to the Control of Vibrations at Work Regulations (2005), which means a risk assessment, awareness training, control actions and health surveillance where necessary.

In another case, it was reported that a business had indeed gone to the effort of getting reliable vibration information (from a reputable tool database) but stopped at that point; the employee could not explain the reason for this abrupt halt? They failed to carry out a risk assessment and so seemingly not met their statutory obligations. Without a knowledge of the risks, an action plan for control could therefore not be established and so the business was none the wiser. Their initial efforts in gathering data was a total waste of time and money!

In a third case, an organisation was looking to carry out their own vibration measurements on their inventory of tools. When quizzed further, this employee lacked confidence in the capability of his business to carry out a competent risk assessment. In an unrelated case, measurements were undertaken using inappropriate instrumentation, where this kit was actually intended for condition monitoring and therefore measuring the wrong thing!

A false economy?

Now let’s not tar all companies with the same brush, there are many examples of businesses that Essel has worked with, who put staff health and wellbeing as one of their highest priorities. These businesses fall well within the law when it comes to regulatory compliance.

But the main impression from our recent experience is that businesses are in denial about HAVS as a health risk in their workplace. With the regulations in place for nearly 15 years, surely any reputable business or health and safety manager should not be unaware of the risks of HAVS due to regular use of powered tools?

A further impression was that cost was regarded as a primary restricting factor when it came to carrying out a competent HAV risk assessment. With fines now in six figures and rising (the latest prosecution was a record £600k), plus the risks of compensation, think ‘no win no fee’, this is a false economy. Investing in competence training or alternatively getting external help has an obvious ROI.

But above all, is it not a MORAL responsibility for businesses to look after the health and wellbeing of their staff?

A free guide to conducting a hand arm vibration (HAV) risk assessment is available for download. It explains, amongst other things, when you should carry one out, and what constitutes a competent risk assessment. Click here to receive it.

It’s well known that hearing damage may be caused by exposure to loud noise, and that the degree of damage is more severe the longer the period of exposure is to noise. What may not be common knowledge is that there is strong evidence that some chemicals (known as ototoxicants) including medicinal drugs could cause hearing loss or imbalance when exposed to them. These effects are independent of noise and may be either temporary or permanent.

It therefore follows that exposure to both noise and ototoxic substances elevate the risk of hearing loss, and this needs to be recognised when carrying out a noise risk assessment.

How is the hearing mechanism affected by ototoxic substances?

Ototoxicants may enter the body by inhalation, ingress through the skin, or ingestion, and eventually find its way into the bloodstream. It may then damage the inner ear by either affecting the structures in the ear itself, or by affecting the nervous system. Some of these ototoxicants may damage the hair cells in the cochlea (i.e. the auditory receptor located in the inner ear) where the hair cells are responsible for transmitting signals to the brain along the auditory nerve. These type of ototoxicants may be classified as cochleotoxicants. There are 2 further types of ototoxicants, viz: neurotoxicants which can inflict auditory damage via the central and peripheral nervous system, and vestibulotoxicants which affect the balance sensors in the ear and result in imbalance. This may be accompanied by dizziness and vertigo.

The detrimental effect of some ototoxic substances upon hearing is that in addition to sounds needing to be louder for detection, it creates both the inability to localise auditory signals and poor frequency resolution which contribute to further hearing impairment. Consequently, in noisy environments, the chances of accidents are heightened for those affected.

Which substances are ototoxic?

Current investigative work into the interaction of ototoxic chemicals with noise is limited and is based on epidemiological studies from humans and also animal research. Where data has been taken from animals exclusively and research bodies have considered the test methods to be robust and reliable, there is a high degree of confidence that the tested substances may be regarded as ototoxic.

Ototoxicity may be present in the following groups of substances. Some of these substances may not be out of place in industrial type environments. The lists are by no means exhaustive:

Solvents

• Styrene and methylstyrene
• Trichloroethylene
• n-propylbenzene
• Toluene
• Xylene and p-Xylene
• Ethylbenzene
• Carbon disulphide

Asphyxiants

• Hydrogen Cyanide
• Carbon monoxide

Nitriles

• 3 Butenenitrile
• cis-2-pentenenitrile
• acrylonitrile
• cis-crotononitrile
• 3,3 iminodipropionitrile

Metals and compounds

• Lead
• Germanium Dioxide
• Mercury

Medication

• Aminoglysocidic antibiotics (e.g. streptomycin, gentamycin, amikacin)
• Analgesics and antipyretics (e.g. chloroquinine, quinine and salicylates)
• Loop diuretics (e.g. furosemide)
• Chemotherapy agents (e.g. cisplatin, bleomycin, and carboplatin)

Of the medication, ototoxicity may be temporary and mild in small doses but the effect may be more pronounced with consumption of some of the chemotherapy agents used in managing cancer. With an ageing working population, employees could be under such medication regimes.

Which are the high-risk industries?

These are some examples of industries where ototoxic substances are used, and where noise levels can be high, therefore increasing hearing loss risks.

• Fabricated metal manufacture
• Aircraft refuelling
• Textile manufacture
• Furniture building
• Printing
• Paint manufacture
• Construction
• Boat/Ship building
• Chemical production
• Firefighting
• Paint production
• Defence (weapon discharge)
• Leather production
• Solar cell manufacture
• Mining

How can ototoxicants be identified in the workplace?

Research bodies have concluded that current studies do not provide enough robust evidence to be able to publish a dose-effect combined relationship of noise with ototoxicants. Neither The Control of Substances Hazardous to Health Regulations (CoSHH) 2002 nor the Workplace Exposure Limits (EH40/2005) refer to ototoxicity. It’s therefore highly unlikely, for commercial reasons, that manufacturers will warn of ototoxicity on their products. This makes ototoxicants difficult to identify and therefore to apply methods of risk control. The best clue for ototoxicity would be to look out for the word neurotoxic on the product labelling or the safety data sheets.

How do you reduce the aggravation of hearing loss with ototoxicants present?

Some suggested risk mitigative actions employers should consider carrying out in a noisy workplace where staff are in contact with ototoxic substances are listed below.

• Replacing ototoxic chemicals by less ototoxic ones or ones that are not ototoxic.
• Isolating the process from the noisy environment if use of the ototoxicant cannot be avoided.
• Providing information in the risks, hazards, and effects of ototoxic chemicals with noise to employees.
• Increasing the frequency of health surveillance for staff exposed to noise and ototoxicants.
• Providing adequate ventilation and effective PPE in areas where ototoxicants are used.
• Raising staff awareness in the effect of ototoxicant medication upon hearing, and for them to inform their doctors/pharmacist of any concerns.
• Introducing any noise control measures against slightly reduced regulatory exposure limits.

What else should be considered when carrying out noise risk assessments in a workplace? Click here to find out more by receiving a guide on what other things you need to consider when carrying out a noise risk assessment. The guide also includes how to identify hearing protection overprotection, which may be a hazard in the workplace.

Essel Acoustics has the expertise to carry out full and competent noise risk assessments in your workplace and can recommend appropriate noise control so that you can fulfil your obligations in accordance with the Control of Noise at Work Regulations (2005) . Contact us for any assistance on this.

A previous blog explained how the SNR (Single Number Rating) figure of a CE approved hearing protector was used to predict the amount of hearing protection provided. It also suggested exercising caution using the SNR for the prediction if the offending noise was excessive in high or low frequencies. Only one value, the equivalent continuous ‘C’ weighted sound pressure level was required for the prediction exercise.

For noise content rich in high and low frequencies it may be preferable to use the HML method instead for predicting the hearing protector attenuation, but the sound level meter that is measuring the noise must be capable of at least capturing ‘A’ weighted and ‘C’ weighted sound pressure levels (if it has no facility for taking octave band measurements).

The HML of a hearing protector (CE approved) specifies 3 values, viz. High (H), Medium (M), and Low (L) which usually accompany the product packaging, and these values are derived from the octave band attenuation performance of the hearing protector using an ISO standard.

This HML method takes into account the spectral characteristics of the offending noise when measuring the equivalent continuous ‘C’ (L_Ceq) and ‘A’ (L_Aeq) weighted sound pressure levels. Computation of (L_Ceq – L_Aeq) shall be applied to the next stages of processing for predicting the attenuation. Prediction of the hearing protector attenuation is a two stage process, where firstly the Predicted Noise Reduction (PNR) is determined as follows:

The second stage of the process is:

L_Aeq’ = L_Aeq – PNR

where L_Aeq’ is the noise level predicted ‘underneath’ the hearing protector. The HSE recommend adding 4dB to this noise level to allow for ‘real world’ factors such as improper wearing of hearing protection and interference (particularly when wearing earmuffs) from other forms of headwear such as glasses and earrings.

As an example, for a hearing protector (where H = 25dB, M = 18dB, L = 13dB) in a noise field where L_Ceq = 103dB, and L_Aeq = 104dB, we have (L_Ceq – L_Aeq) = 103dB – 104dB = -1dB (which is numerically less than 2dB).

Therefore, from equation …(2) above, PNR = 18dB – [0.25(25 – 18)(-1 -2)]dB = 18dB – (-5.25)dB = 23.3dB

Hence L _Aeq’ = 104dB – 23.3dB = 80.7dB (or 81dB to the nearest whole dB).

Allowing for the ‘real world’ factor of 4dB, an 85dBA noise level is predicted ‘underneath’ the hearing protector. You may find it more convenient to use the HSE Hearing protection calculator spreadsheet on http://www.hse.gov.uk/noise/calculator.htm, under the “HML” tabbed worksheet.

Important! The L_Ceq measured quantity is different to an L_Cpeak one also seen on sound level meters and should not be confused with one another. The latter is a ‘C’ weighted absolute peak measurement where high peak levels may present a risk to hearing from a physical damage point of view. The selection of appropriate hearing protection against such damage uses a prediction method (which also uses the HML data) that is different to the one described in this posting.

It should be emphasised that the octave band method of predicting attenuation is regarded as the one that’s most accurate. To use this method your sound level meter must have the capability to measure noise in octave bands.

Essel Acoustics has the skills, experience and qualifications to carry out a noise risk assessment which will include recommending the appropriate hearing protection (if its use cannot be avoided) for staff working in your environment, to fulfil regulatory requirements.

The ill effects of hand arm vibration depend upon the vibration magnitude of the tool and the user’s duration of exposure, and both these factors contribute to the Daily Vibration Exposure, A(8).

From a control point of view the most effective method of reducing A(8) and the risk of contracting HAVS (Hand Arm Vibration Syndrome), is to reduce the vibration magnitude experienced by the employee. If all possible steps in vibration reduction have been tried, but a residual risk remains, then an organisational change such as ‘job rotation’ or task sharing may be an option to consider.

This blog demonstrates an example of how ‘job rotation’ can help reduce the A(8) experienced by employees using power tools. The example, which could be encountered in real life, makes use of the HSE ‘Ready Reckoner’ points system in the analysis which is a fairly simple computation procedure to follow.

Steps to take for reducing the Daily Vibration Exposure, A(8)

Some possible methods of achieving vibration reduction are by:

1) eliminating the high vibration emission process or substituting it by one that gives off lower vibration.

2) replacing the tool by one that emits less vibration (but which is at least as equally efficient in carrying out the assigned task).

3) maintaining tools and replacing worn consumables.

If the vibration magnitude cannot be further practicably reduced after trying the above steps, then the next step might be to consider the introduction of an organisational change by limiting the time individual members of staff are exposed to vibrations from tools or processes. This may be achieved by sharing the task between employees, through ‘job rotation’. An example of how this would apply is shown in the section below.

An example

In a typical landscape gardening business, there are four members of staff each carrying out a separate task using a hedge trimmer, a chain saw, a brush saw, and a mower. Vibration magnitudes of these various tools were either extracted off a database or measured (in accordance with BS EN ISO 5349) and the daily use duration (or equipment activation time) for each tool was measured either through observation or obtained from staff filled record sheets. A(8) values could then be established.

The HSE online exposure calculator in the form of an Excel spreadsheet is available on http://www.hse.gov.uk/vibration/hav/vibrationcalc.htm and is used to calculate A(8) in terms of exposure points for each member of staff carrying out their task using a particular tool.

A snapshot of the ‘Hand Arm Vibration Calculator’ spreadsheet is shown in Table 1 below, and for each tool vibration data and exposure durations (i.e. daily use) have been entered (white cells). The figures in the yellow cells are the automatically evaluated exposure points and the darkened cells are to be disregarded.

Table 1 – Daily exposure points for tool operation

In accordance with the Control of Vibration at Work Regulations (2005), the exposure points that correspond to the action and limit values are, respectively:

• 100 points [this corresponds to the Exposure Action Value, where the Daily Vibration Exposure, A(8) = 2.5m/s²]
• 400 points [this corresponds to the Exposure Limit Value, where the Daily Vibration Exposure, A(8) = 5.0m/s²]

It can be seen that the employee who uses the Chain Saw daily, exceeds the Exposure Limit Value (ELV) (with 613 exposure points), whilst those employees using the Hedge Trimmer and Brush Saw exceed the Exposure Action Value (EAV) (with 225 and 305 exposure points respectively). The operative using the Mower is subjected to less than the EAV. According to the Regulations, when the ELV is exceeded, steps shall be taken to reduce A(8) to below the ELV. Note that health surveillance and information, instruction and training in HAVS shall be provided to all those exceeding the EAV.

Re-organisation of tasks

To ensure that no operator is exposed to vibration exceeding the ELV,  a solution could be to share the four tool operations equally between the four operators (i.e. each operator shall use two tools) by way of a ‘job rotation’ process. Any operator shall use a tool for only half the daily use or exposure duration which arithmetically equates to halving the exposure points.

An amended calculation in Table 2 below shows how the exposure points have been reduced by half when halving the exposure duration per tool.

Table 2 – Daily exposure points for tool operation after reorganisation through ‘job rotation’

To decide which combination of tool usage is most suitable, the exposure points for each tool as a result of using the tool for half its daily use may be fed into Table 3 below. We have:

Table 3 – Tool combinations with Total Exposure points

Preference should be given to the Chainsaw/Mower and Hedge Trimmer/Brush Saw combinations since these are slightly lower than any other combinations. In other words, the Mower operator should swap roles with the Chainsaw operator when half the exposure durations have been reached for both tools. The same principle will apply regarding the Hedge Trimmer and Brush Saw combination. None of the operators will now be subjected to vibration above the ELV, however note the following:

a)  For the ‘job rotation’ process to be considered as an acceptable method of control, it must be established that the original mower operator is either not showing symptoms of HAVS, or is particularly vulnerable to this injury now that his A(8) has increased. Health surveillance should identify this.

b) After the introduction of ‘job rotation’, health surveillance together with suitable and sufficient information, instruction and training (including how to report signs of HAVS) should now be legally provided to the original mower operator as his A(8) will exceed the EAV.

A good risk assessment should take into consideration the possibility of recommending organisational changes such as ‘job rotation’ as part of the hierarchy of vibration control, if the vibration magnitude cannot be practicably reduced.

A free guide to conducting a hand arm vibration (HAV) risk assessment is available for download. It explains, amongst other things, when you should carry one out, and what constitutes a competent risk assessment. Click here to receive it.

In a couple of blogs posted not long ago, overprotection⁽¹⁾ and the need for situational awareness⁽²⁾ were given as possible reasons why staff consistently failed to wear their hearing protection in high noise environments. There may be other valid reasons for this and comfort, or rather the lack of it may be one of them.

Perhaps you’ve selected a particular hearing protector (appropriately rated, one would hope) for employee use. However, wearer dissatisfaction grows due to many factors and your chosen hearing protector ends up not being worn, or not being worn properly. Consequently, exposure to noise returns as a risk.

Offering choices

It may have been beneficial instead to have offered staff a choice of the correctly rated hearing protection as a trial exercise, requesting their feedback. This allows the opportunity for employees to select a hearing protector most suited to them. In this way they may feel that their chosen model is more personal to them, and this  encourages them to wear it at all times.

As it’s highly unlikely that earplugs or earmuffs alone can satisfy the needs of any particular working environment, samples of both should be supplied for the trials.

Advantages and disadvantages of using earplugs and earmuffs

There are advantages and disadvantages when using earplugs and earmuffs that both you and your employees should be aware of, and this may assist in the selection process. For example, fitting of earmuffs is not as critical to achieve the right amount of protection as is the case with earplugs, but on the other hand earplugs are less prone to interference from long hair, glasses, earrings, and other forms of headgear.

You should, however, be careful of offering too wide a choice of hearing protection as it may make inventory complicated, and spare parts control too.

What are the further advantages and disadvantages that may be associated with earplug or earmuff use? And in which working environment is one type likely to be the preferred choice over the other? Find out by clicking the link below to get your free Factsheet.

We have a FREE Factsheet available here on “Earmuffs or Earplugs – What are the advantages and disadvantages?”

1. https://esselacoustics.com/news/how-hearing-protector-overprotection-could-be-hazardous-in-your-workplace/
2. https://esselacoustics.com/news/staff-not-always-wearing-hearing-protectors-sound-restoration-hearing-protection-may-be-a-solution/

It is commonplace in noisy workplaces to see that earmuffs provided by employers are either being improperly worn or not worn at all.  The frequent complaint (from staff) is that the ear protectors are overprotective in areas that are not continuously noisy, and that this results in poor situational awareness.  Situational awareness is critical for avoiding accidents and possibility fatalities too.  The comment from employees “better deaf than dead” is one that is often heard by Health and Safety managers.

So how can you satisfy the requirements of a hearing protector with the right amount of protection, but not so excessive to make it inaudible to warning or danger signals (e.g. vehicular alarms, equipment malfunction noises), and also to quiet electrically powered vehicles in your workplace? Are you aware that the technology exists commercially in the world of hearing protection to fulfil these needs?  If not, read on.

Sound restoration hearing protection is now available, which, in its most usual form, comes as an earmuff incorporating electronic circuitry plus audio components. The basic operational principle is that it protects against high ambient noise but permits communication and situational awareness during quieter periods.

Miniature microphones mounted on the earmuff pick up low level non-hazardous ambient sounds (which could be warning signals or alarms that need to be heard) and after electronic processing, naturally reproduces these sounds internal to the earmuff via miniature ‘speakers.  This makes it unnecessary to remove the earmuff.  As the ambient sound gets dangerously louder (or even suddenly loud) a compression facility designed in the electronics ‘clamps’ or limits these noises to safe levels at the wearer’s ears.

The benefits of such a hearing protector are two fold i.e. situational awareness together with protection against harmful noise levels.  As the ambient noise gets even louder, the noise breaking into the earmuffs will eventually increase and be determined by the passive attenuation characteristics of the hearing protector.

So providing the earmuff is comfortable to wear, the chances are that this type of hearing protector is likely to stay worn by staff who require both situational awareness and safe hearing protection.  Many of the leading hearing protection manufacturers include such a product in their portfolio.

Essel Acoustics can carry out a noise risk assessment in your workplace and identify appropriately rated hearing protection, and the need for sound restoration types too.  What else should a noise risk assessment consist of?  Click the link below to find out by receiving a free downloadable guide (which also includes a section on hearing protector overprotection)

Download the FREE guide to Overprotection and Noise risk assessment here

Nowadays there is increased awareness of HAVS in industry, but despite this, some businesses still have lack of a meaningful strategy in place to deal with this potential health problem. The Control of Vibration at Work Regulations (2005) places legal duties on employers to protect staff at risk from HAVS.

HAVS is a debilitating and compensable injury caused by frequent exposure to vibration emissions through the use of power tools, for example, angle grinders, impact wrenches, air chisels, strimmers and hedge cutters. If left unchecked, excessive use of such equipment will eventually lead to irreversible damage of the blood vessels and tissue in the hand and arms.

If your business is one that hasn’t given HAVS much thought, or if it has but without a robust plan to deal with it, then take a few minutes to consider the impact of the lack of action should any HAVS related problems arise. The impact is not only a financial one, but it has other effects too.

The many points to consider are listed below.

Financial impacts

• Sickness payments
• Payment of compensation to the injured party
• Costs of medical treatment
• Early retirement and pension costs
• Fines/penalties imposed by enforcement agencies

• Costs to cover for redeployment of internal staff or use of agency supplied staff
• Overtime costs
• Legal costs
• Lost contracts or penalty clauses on delayed contracts
• Investigative and monitoring costs
• Increased liability insurance premiums

Other impacts

These might be difficult to quantify fiscally but would certainly be felt by the business.

• Decreased productivity due to staff being absent for prolonged periods
• Temporary or new staff (if inexperienced) requiring training or management
• Poor morale of workforce
• High turnover of staff
• Bad publicity in press
• Failure to attract new employees, or retain good ones
• Other businesses unwilling to outsource work/processes to yours as a result of your poor safety record

Also, do not underestimate the management and administration costs involved in many of the above items listed. But above all what about the HUMAN cost!

What can you do about it?

If you have had a risk assessment carried out (by someone competent), it should have recommended controls to implement for offering protection against HAVS. You should ensure that the recommendations are implemented.

A free guide to conducting a hand arm vibration (HAV) risk assessment is available for download. It explains, amongst other things, when you should carry one out, and what constitutes a competent risk assessment. Click here to receive it.