Industrial Noise & Vibration Centre

+44 1753 698 800

Technical Notes - Noise

These are detailed technical notes describing what constitutes "best practice" for each topic.

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  • chiller fan
  • compressor

Chiller noise control

Chiller unit noise control

Sound file: typical chiller low-frequency noise reduction,

The noise from chillers, air conditioning plant, condensing units, HVAC, heat exchangers, dry coolers etc provides a host of opportunities to waste resources on inappropriate noise control measures that either don't work or that reduce efficiency - or both. In our experience, a substantial proportion of the noise reduction measures used on these units (acoustic enclosures, silencers and barriers) are simply ineffective as they address the wrong problem.

There are only 3 types of noise generated by these systems: broadband air noise, compressor tones and low-frequency fan hum. The hum, for example, cannot be addressed using silencers and barriers, and yet these are often mistakenly fitted at great capital and running cost (reduced efficiency).

10 minutes with a smartphone is all it takes to avoid costly mistakes by determining which sources require treatment and what is the best noise control option for the particular problem. Anyone can do this.

This approach not only dramatically reduces typical noise reduction project costs, but it can even substantially improve system efficiency (by 23% on one data centre application). Find out how best to reduce the noise from chiller, condensing, cooler and related units here >

  • cooling tower

Cooling tower noise attenuation

Cooling tower noise reduction - gearbox

The key to effective cooling tower noise reduction is accurate diagnosis. Far too often, noise control measures are selected without a clear understanding of -

  • the type of noise problem: is it simply the overall dB(A) level or is there tonal character such as a low-frequency hum?
  • the source of the noise: fan (broadband or tonal); falling water; pumps (often tonal) and/or gearbox noise (tonal)

As a result, far too many noise control projects end in costly failure or go through a number of iterations before the problem is solved. Accurate diagnosis is not rocket science. Forward a few photographs and a smartphone video clip to us by email and we can provide a precise and accurate remote noise control diagnosis plus the optimum costed noise control options within an hour. At no cost.

There is also new low-cost aerodynamic technology that cuts the noise from cooling tower fans whilst often improving efficiency (unlike silencers and barriers that reduce efficiency).

Find out details of the best options to control the noise from cooling towers here >

Our fan technology is saving megawatts per day

environmental noise control

Across the world, organisations using our aerodynamic fan noise control technology are currently saving megawatts of power as a result of the efficiency gains they have realised, compared with both conventional noise reduction technologies and in some cases, compared with unmodified fans.

Coupled with our remote control of noise services that do not require site visits in order to diagnose and implement best practice in noise control (avoiding flight and other transport carbon costs), a key objective is to use our innovative technologies to help clients to reduce their carbon footprints and thereby to render INVC a carbon-negative consultancy.

  • noise control
  • noise analysis
  • environmental noise
  • EHO
  • environment agency
  • environmental vibration
  • remote control

EHO and EA - faster, simpler problem solving

noise in the environment

We provide extensive specialist technical support, information and training on noise and vibration to both regulators (Local Authorities and Environment Agencies) and to industry. As we regularly deal with the same noise and vibration problems encountered, we have probably solved your problem already.

Our acclaimed range of EHO / EA specific noise workshops can help transfer time saving best practice techniques and technology in-house. This approach typically reduces the time to resolve noise complaint and other problems from months or years down to weeks - or even as little as days in some cases... This dramatically reduces the resources spent (freeing them up for other work) and also the time that local residents spend suffering unnecessary stress from unacceptable environmental noise.

We provide a worldwide service via the internet and smartphone technology. Make use of our Remote Control of noise service for a free 2nd opinion and evaluation of best practice - or contact us for advice.

Best Practicable Means / Best Available Technology evaluation service

Complaints or noise nuisance: how do you determine what constitutes “best practicable means” to mitigate. Companies employ consultants to generate reports claiming the cost of mitigation is too high to be practicable. In most cases, the suggested noise reduction technology is not best practice. Our definitions of low-cost BPM are game changers for regulators as problems can usually be resolved within weeks, saving time, resources and money.

We are quite happy to provide definitive definitions of what constitutes BPM/BAT with complete technical justifications, in court if necessary.

Noise and vibration training workshops

We provide very effective training for EHOs and Environment Agencies, from workshops to full CIEH environmental noise competency (some councils have profited from hosting in-house versions by inviting other authorities). These include:-

  • BPM / BAT noise workshop
  • Fan noise control masterclass
  • Venue noise assessment workshop
  • Noise recording and analysis workshop

The Delegate View: “one of the most relevant and informative courses in a long time..” .. “I’d hate to come up against you in court! .. the best value seminar we’ve ever been on” – “standard of presentation was excellent .. humorous and entertaining .. highly recommended”

Digital Noise Assessment (DNA) – automate noise reporting

ppe sign ticked

The Digital Noise Assessment (DNA) provides benchmark report templates covering all the requirements of the noise regulations – including the plan of action. Used either in-house or by consultants as standard format for all updates, it makes noise data easily accessible so that you can find and use the information fast. It features:-

  • DNA report “best practice” template: cut-and-paste from the customisable template Word document
  • Action Plan summary: editable managers’ action plan summary to track implementation of risk management
  • Technical Notes: up-to-date technical notes on regulations, PPE, dose calculations, health surveillance, Buy Quiet, noise control, training
  • Example Report: completed pdf report example including factory plan noise levels
  • Noise Control Audit: if you don’t have the technical background for this mandatory regulatory requirement to make a cost / benefit analysis of the noise control options, we can provide this as an add-on service. Contact us to discuss.

HSE - PPE is an unreliable risk reduction option

PPE hearing protection performance

It has been known for decades that it is virtually impossible to guarantee adequate protection from hearing protectors at noise levels above c 95dB(A). Consequently, it should not have been news that research by the Health and Safety Laboratory (report RR720) proved that the common assumption that PPE is a reliable “solution” to hearing damage risk problems is simply untrue. This assumption has left many personnel at risk and companies are open to claims if their hearing conservation policy is based on PPE use. Some of the key findings of the research are:-

  • PPE in 25% of the companies visited was so ineffective that it provided negligible or no protection for most
  • even in companies with effective PPE use, 14% of workers did not wear protectors when and where required
  • 40% of the workers who should have been wearing protectors got no protection at all

hearing damage claim costs

The inadequacy of PPE performance in many real-world situations is also born out by the continuing tidal wave of hearing damage claims of £400 million in one year (2014 - IFA UK deafness working party), despite (or even because of) the over-reliance on PPE without understanding the performance limitations away from the lab. This also brings into sharp focus the need to reduce noise levels to reduce risk, even when the levels cannot be reduced to below 85dB(A).

As a rule of thumb, provided effective (and time-consuming) management systems are in place, most good quality PPE can be made to work up to noise levels of around 95dB(A). Above this level, it becomes increasingly difficult to guarantee sufficient protection and above c 100dB(A) it becomes virtually impossible.

The key (and very often missing) factors necessary to improve real world protection are:-

  • you must have a system in place to audit wear rate. It is unbelievable that most organisatons do not log wear rates and consequently have no idea of the effectiveness of their PPE. Where appropriate, use the latest generation of intelligent PPE that logs wear rate and attenuation automatically.
  • you must train staff in the correct fitting and use of PPE. This is particularly critical for ear plugs where the assumed protection of 30dB (manufacturer) often drops as low as 3dB in use.

In conjunction with the above, most organisations can cut risk by 50% - 90% at little or no cost (or even at a profit) by introducing very low-cost engineering noise control measures to reduce noise to levels at which PPE can be made to work. For example, reducing noise by 3dB from 97dB(A) down to 94dB(A) halves the risk (and PPE is more effective). Reduce the noise by 6dB and the risk falls by 75%.

Contact us if you'd like to discuss optimal hearing damage risk reduction strategies for your organisation.

There is more on the topic of self-financing noise control, including a White paper here.

Download a detailed article on inadequate real-world PPE performance >

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