Industrial Noise & Vibration Centre

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The Noise Control Audit (NCA) - cuts costs and NIHL risk

The cost-benefit analysis you need to optimise noise risk reduction

Sad fact: the general standard of hearing damage risk reduction advice is abysmal. Consequently, many people continue to suffer unnecessary hearing damage. Discuss...

The general standard of noise risk mitigation reporting is truly awful. The Environment Agency recently published the results of a survey of the quality of reports from noise consultants, 95% of which were deemed inadequate (60% were deemed extremely poor). A past HSE survey of occupational noise risk mitigation reporting produced similar results.

As the noise consultancy industry is predicated on measurement, virtually the only risk mitigation measure ever recommended is based on PPE. The Hierarchy of Control (HoC) requirement that noise control should be the priority requirement is almost invariably ignored.

Consequently, organisations currently waste resources on measures that are not cost-effective, are not best practice, and do not adequately protect against Noise Induced Hearing Loss ( NIHL).

Instead of expenditure on repeated placebo noise surveys that tell you what you already know (you still have a problem) and provide advice based solely on PPE (that is often ineffective), invest in a Noise Control Audit (NCA) to provide the information you need to reduce both costs and Noise Induced Hearing Loss (NIHL) risk at source.

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Noise Control Audits are a regulatory requirement

rip ppe

This is a regulatory requirement. PPE cannot be used as a long-term risk management measure unless you can prove that noise control is not practicable. Has any organisation ever had a noise risk management report that includes the results of a Noise Control Audit (NCA) cost/benefit analysis? Almost certainly not as they assume that the recommended PPE will provide adequate protection. HSE and other research has shown that the typical real-world attenuation is a only small fraction of that assumed. Consequently, users can still suffer Noise Induced Hearing Loss (NIHL).

The required Noise Control Audit involves the following process:-

occupational noise control industrial site

For a whole site

Initial contact

  1. Forward recent previous noise assessment or survey reports
  2. Discuss the objectives and operational factors with site engineers
  3. We then forward a costed proposal to carry out a Noise Control Audit on part, or all, of the site. This will often include initial comments re the potential for noise control based on extensive previous experience.

noise control audit cost benefit report

The Noise Control Audit

  1. Initial visit to carry out diagnostic noise and vibration measurements and to discuss operational constraints in detail. This allows all the potential noise sources in each priority item of plant to be ranked in order of their contributions to the overall level.
  2. Once the results have been analysed, then the conclusions are provided in a brief report that includes the following elements:-
  • an outline of all the noise control options for each item of plant
  • the estimated implementation costs for each of the options
  • the likely noise reduction that would be achieved by each option
  • the operational, hygiene and productivity advantages/disadvantages (where appropriate) for each of the options

Where noise control is not practical, we can provide "you are doomed" certification to justify the use of PPE.

Noise control programme implementation

Once the Noise Control Audit is complete and the preferred options selected:-

  1. Carry out additional measurements (as required), trial mock-ups (in some cases) and discuss the options in detail with company engineers re operational and other practical constraints.
  2. Provide detailed noise control recommendations for the selected options including outline drawings, materials specifications and potential suppliers (but not manufacturing drawings).
  3. Liaise during implementation to ensure optimum performance of the modifications on each type of machine. Once implemented on one machine or line, they can then be copied across to any other similar units at low cost.

Note: the noise control recommendations are provided as a working document with sufficient information so that the noise control modifications can be implemented by any competent engineer (in-house or local contractor) - often as an extension to normal maintenance.

For a single item of plant

Initial contact

smartphone analysis of hydraulic power pack noise
  1. Forward recent previous noise assessment or survey reports
  2. Email photos and a short smartphone video clip of the plant in operation
  3. Discuss the objectives and operational factors with site engineers
  4. We then forward a costed proposal to carry out a Noise Control Audit on the machine. This will often include comments re the potential for noise control based on previous experience - and may not even require a site visit, saving time and money.

Noise Control Audit and noise control implementation

This involves the same process as described above.

The Noise Control Audit benefits

The results of the NCA allow you to make an informed decision as to the optimum NIHL risk reduction programme - in advance of committing expenditure. There are 3 types of scenario post NCA:-

field protection provided by hearing protectors
  1. PPE can be eliminated across an entire site by reducing noise levels to below 80dB(A). Future NIHL risk eliminated with large cost savings and improved working conditions.
  2. PPE use can be eliminated in some areas and reduced across other parts of a site. NIHL risk reduced, typically by 70% - 90%, potential cost savings and improved working conditions.
  3. Noise levels can be reduced, but remain above 85dB(A) so PPE is still required. However, PPE is now capable of providing adequate real-world attenuation to minimise NIHL risk. Reduced noise levels provide the following risk reductions:-
  • -10dB - 90% risk reduction
  • -7dB - 80% risk reduction
  • -5dB - 70% risk reduction
  • -3dB - 50% risk reduction

Important note: typical real-world PPE attenuation is 3dB - 10dB. Consequently, they typically provided reliable protection (to below the regulatory 80dB(A) Lower Exposure Action Value (LEAV)) up to noise levels of around 83dB(A) - 90dB(A).

In many cases, noise control programmes implemented as a result of NCAs will pay for themselves quite quickly.

Noise Control Audit: the cost-benefit analysis method

The following are the steps involved to generate an accurate cost-benefit analysis of the noise control options. Each step generates the information required to evaluate and cost the options for comparison with the costs and efficacy of continuing with an existing PPE based programme. Organisations will often find that the recommended noise control programme will:-

  • provide a higher risk reduction than typical PPE based programmes
  • pay for itself within 1 - 5 years, making it the self-financing and profitable option

Step 1: evaluate your actual PPE attenuation and capital costs

Unless you can prove otherwise, you should assume your PPE is only providing 5dB - 10dB attenuation at most. The key "prove otherwise" element is based on your current (regularly) measured and documented real-world wear rate (not the assumed wear rate) plus the additional factors shown in the graphic. The other option is to use the latest intelligent PPE that provides this information automatically.

We use our real-world PPE performance calculator to assess the actual attenuation. In this illustration, £9k is being spent per annum to provide an attenuation of 4.9dB, not the 24dB assumed protection based on the supplier specification.

Step 2: engineering evaluation of the noise control options and costs

From the detailed noise and vibration measurements for each item of plant and discussions with site engineers, we estimate both the practical noise reduction that can be achieved and the likely implementation costs (materials and fitter man-hours). Due to the diagnostic process we use coupled with extensive past experience, these results are usually very accurate.

In this example, all noise levels would fall to well below 85dB(A) for a total implementation cost of c £28k with maintenance costs of £3k/pa and a compressed air saving of £1k/pa. Moreover, the operator noise doses would all be <80 LEP,d i.e. no PPE required.

Step 3: estimate your total PPE based hearing conservation costs

Very few organisations have an accurate idea of how much is spent on PPE, including both the direct and the indirect costs listed here. This is a very useful, not to mention eye-opening, process, particularly when compared with the actual attenuation provided by the PPE as calculated in Step 1.

In this case, the estimated true cost is around £15.5k/pa to achieve an average attenuation of only 4.9dB... Is that good value?

Step 4: calculate current cumulative hearing conservation v noise control costs

Combine the above data to calculate the cumulative costs for both the current hearing protection and for the potential noise control programmes over the next few years.

Step 5: use the Noise Control Audit data to generate your cost/benefit analysis

Finally, plot the cumulative costs for both PPE and noise control programmes to generate the cost-benefit analysis required to make a judgment as to the optimum cost-effective Noise Induced Hearing Loss risk reduction strategy. In this example:-

  • noise control cuts the risk substantially more than current PPE
  • noise control would pay for itself within c 2.5 years compared with the existing PPE policy, saving £53k over 6 years
  • non-financial benefits: no NIHL risk, no PPE, better working conditions and communication, no admin hassles etc