Industrial Noise & Vibration Centre

+44 1753 698 800

Fan Noise Reduction

Fan noise reduction - no silencers, no maintenance, more efficient

Self-financing fan silencing makes use of innovative aerodynamic noise reduction techniques instead of silencers. Installed in a multitude of fans and blowers across the planet, from 6cm diameter to 4MW behemoths, this technology has and is saving £millions in capital and reduced running costs. Retro-fitted in hours, our muffler alternative is particularly effective at fan hum attenuation, providing stealth and efficiency to reduce energy consumption and carbon footprint compared with attenuators.

Take advantage of our free email evaluation service to determine if you can design-in or retro-fit our technology to your fans (see how Quiet Fan technology works). We provide instant diagnoses based on smartphone data (Remote Control of Fan Noise) followed by the solution anywhere in the world, so we can solve your problem wherever you are based.

Fan noise reduced by 99% and costs by 80% using new technology

We received the Rushlight Noise Abatement Award for innovation in environmental noise control by applying our noise reduction technology to three 4MW industrial fans at a Tata steel-works. As well as eliminating a long-running environmental noise problem, Tata also reduced its capital costs (>£800,000) and running costs (c £200k per annum) compared with silencers. It is equally applicable to chiller and data center cooling fans where efficiency gains of up to 23% have been achieved. Applied more widely, the technology has the potential to contribute to a significant reduction in worldwide CO2 emissions.

Contact us to see if our technology is applicable to your fan noise problem. If it is, in principle you could be running a quiet fan in less than a week from first email at a tiny fraction of the cost and at higher efficiency than traditional attenuators and enclosures.

Quiet Fan Technology – industrial fan noise reduction without silencers

Industrial fan silencing technology reduces tonal noise at source at a fraction of the cost of traditional techniques such as silencers and enclosures. It achieves this noise reduction without the increased power consumption associated with conventional attenuators, lasts the lifetime of the fan without maintenance and can be retro-fitted in a down-time of hours. Applications include extract fans, ID fans, data centres, chillers, air conditioning plant, process ventilation fans, cooling towers, HVAC, power stations, cement and steel works and most blowere where there are low-frequency noise issues.

Industrial fan noise attenuation: how does the technology work?

Originally developed for the Euro-fighter, we take a similar approach to Formula 1 teams who invest in aerodynamic aids to control airflow round cars. Fan noise is turbulence generated pressure fluctuations shed by the impeller. We reduce these at source by designing aerodynamic inserts that fit inside fan casings. This reduces the noise at source without the back-pressure often associated with silencers. As source control simultaneously reduces intake, exhaust and blower casing radiated noise, it may eliminate the need for both attenuators and acoustic enclosures or lagging.

Fan noise attenuation: remote control anywhere on the planet

Fan or blower noise reduction problems can be solved anywhere on the planet via the internet - saving the time and money of site visits. The whole world now has instant access to this noise and energy-reducing technology. Successful projects across the globe include 5 large fans at this USA oil refinery where we reduced the noise reduction project capital cost from $1.25 million down to <$0.25 million… Go to Remote Control of Fan Noise for case studies and details of the smartphone email information needed to diagnose if your project could benefit from this innovative technology.

Free Remote Diagnosis

Email us a video from your smartphone for an evaluation of best practice

Your problem may already be solved

Search our worldwide best practice options

Keep current with best practice innovation

Subscribe for the latest in techniques and best practice

Tata steel gas fan stack noise attenuation

3 off, very large, 4 megawatt steelworks fans had been the cause of environmental noise issues for years. The problem was solved within months at a tiny fraction of the cost of attenuators by implementing our aerodynamic fan noise reduction technology. Fan power consumption was also reduced, making this a self-financing project.

A second opinion saves a £million…

The fans generated a low-frequency hum (c162Hz) over a wide area. As the fan speeds varied, sophisticated resonator silencers were ruled-out and conventional attenuators would have imposed a heavy penalty in terms of cost and reduced fan efficiency. Tata approached us for a second opinion as to potential alternatives. Our solution was to develop novel fan casing modifications, avoiding the need to modify either the existing ductwork or the stacks to fit silencers - thereby minimising downtime. These modifications have eliminated the noise at source for the lifetime of the fans. Significantly, the new fan modifications require no maintenance and do not affect the efficiency of the fan. Moreover, the willingness of Tata to invest in new and innovative technology has reaped very substantial rewards compared with conventional silencing:-

  • 94% reduction in noise (12dB)
  • capital cost savings of over £800,000
  • substantial environmental benefits (carbon emissions)
  • c £200,000 saved each year on running costs (power and carbon)
Scrap extract fan noise reduction

Attenuators do not take kindly to the passage of scrap – which is a problem when installing noisy chopper fans. Our cutting edge aerodynamic modifications, however, are even robust enough to be able to cope with extreme scrap metal. In this example, both occupational and environmental noise problems were simultaneously solved at source. Three sets of chopper fans are used to pull-off scrap cans from the lines and to shred them for recycling. These generated high levels of tonal noise, causing both occupational and environmental noise problems. Instead of fitting conventional fan attenuators, acoustic enclosures and noise lagging at a potential cost of £30k or more, our Quiet Fan technology was fitted to the fans in a matter of hours to give an overall noise reduction of 22dB(A) at an installed cost of c £1000/line – a capital cost saving of 90% and with no effect on fan performance or efficiency.

Unlike fan silencers, the modifications are unaffected by the passage of scrap cans and will last the lifetime of the fans without maintenance – and at less than 1% of the previous noise level…

Red Bull extract fan noise attenuation

Fitting conventional silencers to this fan extract system seemed a long-winded and crude process to Red Bull who were used to the pace of change and the engineering innovation found in Formula One. Our approach was a perfect fit for their engineering ethos – 1000x less noise installed within a pit-stop of a few hours.

Red Bull found an alternative to traditional attenuators in our aerodynamic noise control technology. The aerodynamic inserts were designed, manufactured and installed inside the fan casing within a pit-stop window of just a few hours to dramatic effect. The problem 218Hz low-frequency tone was reduced by a factor of around 1000 (30dB – a new world record for the technique), completely eliminating the problem at the source for the lifetime of the fan, without maintenance and without affecting fan efficiency.

“We felt that there had to be a better way to reduce the fan noise other than by compromising the system efficiency and creating additional long term maintenance” said Terry Brice of Red Bull Technology. “The INVC technique not only produced a fantastic result, but it’s also very satisfying as an elegant engineering solution”.

Combustion fan noise attenuation

Despite considerable time and money being spent with the supplier and acoustic consultant installing silencers and reducing fan speed, a noise abatement notice was due because of numerous complaints about combustion fan noise. We resolved the problem overnight via Barry welding in 22dB of attenuation during a normal shutdown.

Combustion fan noise from a new waste heating system at a Palgrave Brown MDF site had caused numerous complaints from neighbours with a noise abatement notice in the offing. The supplier and their consultants had tried conventional measures (additional silencing, reduced fan speed) over an extended period to no avail. On the point of admitting defeat, they were referred to us. Our solution (controlling the noise at source) was fitted in hours. The next morning, it was hard to tell that the fan was running as the tonal ID fan noise was reduced by 22dB and the overall level by 9dB(A), quickly, permanently and without affecting fan efficiency. The results were so impressive that the director, Alan Fillingham, recommended that our approach should be used throughout the group.

Steelworks axial extract fan noise attenuation

Low frequency tonal noise from 8 architectural scale axial fans (several stories up and already fitted with 8m long silencers!) at a Tata steel-works had caused environmental noise problems over a number of years. We diagnosed, we tweaked – and the problem was solved…

All the possible conventional fan noise control solutions considered (largely additional silencers) would not only have cost a large fortune (and probably not been very effective), but would also have reduced efficiency and therefore increased the running costs. We diagnosed a system resonance which we addressed at source, reducing the tones by 20dB – and with no effect on fan efficiency.

Quarry fan noise reduction - no clogging

A serious problem with conventional silencing for fan applications like this where the air is very dirty is the need to shut-down to clean the silencers on a regular basis with the associated cost implications. Our noise attenuating technology is immune to clogging, so no cleaning needed - ever…

In this instance, the tonal noise from this quarry suction fan working under very dirty conditions was reduced by 23dB using our unique Quiet Fan technology - a new record for the technique. No silencers, no enclosure, no lagging, little down-time and no maintenance - ever (despite the operating conditions). Plus, this all comes at a tiny fraction of the capital cost of conventional silencing and without the associated running cost penalty. This approach to fan noise reduction is particularly effective where the air is dirty as it avoids the need to clean silencers.

Paint shop spray booth extract fan noise attenuation

Paint spray booth extract fan noise control poses a problem for conventional silencing in that, even with effective filtration, the silencer will clog and lose attenuation. Moreover, paint fans often generate a low-frequency hum that passes through mufflers with little attenuation. This case study illustrates a low-cost alternative approach to spray booth extract noise reduction that lasts the lifetime of the fan without loss of performance.

A pair of classic industrial paint spray booth extract fan filter systems used on an MDF paint plant generated a very irritating low-frequency drone that was the subject of complaints both from operators inside the workshops and from local residents. At these low frequencies, conventional silencers would not only have been ineffective, but would have quickly clogged.

Moreover, as the pair of fans were not quite synchronised, the sound also had a distinctive “beat” which made it even more annoying. As the spray booth extract fan noise was at a low frequency of 146Hz, conventional silencers would have been very large, very expensive, would have required relocation of the plant and supplementation with lagging and enclosures (and regular cleaning). We bypassed all these issues by reducing the fan noise at source (Quiet Fan technology), eliminating the tones (13dB reduction) and the “beat ” with no down-time outside normal maintenance requirements. This approach has a broad application for paint plant, spray booth fans and other dust extract filtration systems as a more effective alternative to silencers…

cement works fan and stack noise attenuation

Unfortunately, the plant update to improve the efficiency of the exhaust fans in a large cement works created a serious noise problem that generated complaints from miles around. A novel, low cost attenuation system was designed and fitted over a weekend to avoid the eye-watering down-time cost required to implement conventional solutions.

Conventional stack silencing would have resulted in an unacceptable delay in solving the problem plus massive capital and prolonged shut-down costs. Our alternative solution was based on the design of a set of bespoke stack silencer elements tuned to suit the noise signature. These were pre-fabricated off site and then inserted into the stack through a small access door over a weekend. The result was a 19dB noise reduction over the critical frequency range with no effect on the fan and stack efficiency – and at a small fraction of the cost of conventional silencing.

Thermal oxidiser fan and stack noise reduction at source

Severe noise problems were encountered from a new regenerative thermal oxidiser plant on an industrial site. The suppliers suggested an earth berm noise barrier, large fan silencers and acoustic enclosures that would not only have cost a 6 figure sum, but would have been a complete waste of money as they would not have worked.

We used accurate and precise diagnosis to isolate the key subjective sound features in addition to the broadband noise. We removed the tones; slowed one fan to remove the “beat” with the other unit; moved and changed the damper to improve flow and added small conventional attenuators to reduce broadband noise. These modifications eliminated all the noise character and reduced the overall noise by 15dB(A) at a few % of the costs associated with the traditional (and less effective) noise control package.

Rooftop chiller fan noise attenuation

The cost of reducing the noise from air conditioning system chillers on the roof of a large multi-storey data centre facility to meet the requirements of the Local Authority had been estimated at over £300,000. Fitting the proposed acoustic screens round the condensers would also have required considerable planning (closing streets and bringing-in cranes) and the proposed noise control measures and silencers would have reduced the cooling capacity of the HVAC system. We had a better idea…

The communications company involved approached us in the hope that we could provide a better alternative. A very careful analysis of the noise sources and layout of the air conditioning plant plus some lateral thinking resulted in an elegant solution involving a combination of engineering control at source, novel local acoustic treatments and the clever use of geometry. The result was a set of modifications that were easy to implement in convenient stages and provided a reduction in the condenser axial fan noise of c 15dB(A) at a cost of c £40,000 – and with no effect on the normal operation or the overall efficiency of the system unlike conventional noise barriers and silencers.

More details of the best approach to reducing the noise from data centres, chillers and air conditioning plant >

Axial chiller condenser fan noise reduction

Chiller noise control costs were cut by 80% using new technology. The company running a server farm had spent £100,000 on noise control measures (acoustic barriers and silencers) for their HVAC and AHU plant to no avail – the complaints continued as the noise levels were virtually unchanged. We were invited by the Local Authority to provide both parties with a definitive statement as to what constituted “best practicable means” and to sort the problem.

Careful diagnosis allowed us to generate a best practice noise control package that would eliminate the problem at a cost of c £30k.

These measures included purpose designed silencing, geometry changes, improved acoustic screening and internal modifications to the main Air Handling Units. On the air conditioning condenser units, we by-passed the conventional solution of noise barriers and silencers as these are not only high cost control measures, but they can also reduce the efficiency of the chillers themselves. Our alternative was a set of low cost engineering noise control modifications that not only reduced the overall noise from the HVAC plant at source by 8dB(A), but also eliminated the hum (worth an additional 5dB(A) noise reduction with respect to environmental noise limits) – and with no effect at all on the chiller condenser performance or access.

The result was an overall noise reduction of 12dB(A) and the elimination of the tonal content of the noise from the condensers. If best practice had been used at the start, the company would have reduced the cost of the chiller plant noise control project by 70% and avoided several months of management hassle and a sacking…

More information on the optimum way to reduce noise from server farm, chiller, AHU and data center fans >

Cooling tower fan noise attenuation at source

Cooling tower fan silencing by conventional means is often both very difficult and very costly as the problem is usually low frequency in nature so conventional silencers and noise barriers don’t work. Despite this fact, the cooling tower world is awash with placebo silencers and acoustic barriers that are just a waste of money. Alternatively…

… quite often there are low-cost source control alternatives. For example, the dominant environmental noise problem from a food processing plant in the middle of a village was caused by cooling tower noise from a pair of units – despite the large silencers already fitted to the axial fan exhausts. We devised engineering modifications that produced a substantial improvement in the efficiency of the cooling towers that, coupled with measures to reduce the noise from falling water, not only cut the overall noise level from the units by 15dB(A), but also substantially reduced running costs.

Details of how best to silence cooling towers >

Cooling tower fan and pump noise reduction

The noise from a pair of new cooling towers had ignited complaints from residents across the road from the site. A typical acoustic consultant was drafted-in who recommended the industry default silencers and a noise barrier without carrying out any diagnosis. Not good practice, let alone best practice.

The predicted effect on the plant noise of fitting the typical conventional acoustic package of silencers and a barrier along the edge of the site was to reduce the noise level down to around 56dB(A) at the neighbours - still far too high for the area. Despite a total cooling tower noise attenuation package costing well over £40k, not only would the problem not have been solved but in addition, as the acoustic barrier would have caused serious transport access problems, the company had to look for alternatives.

Our solution was based on a very accurate diagnosis and ranking of the cooling tower fan, drive and pump noise sources to develop an engineering source control package. The final noise reduction measures for both cooling towers comprised:-

  • intake and drive motor modifications
  • exhaust and pump silencers
  • local acoustic screening

This package achieved a noise level of <50dB(A) at a cost of only £6k and without affecting normal site operation or cooling tower efficiency. Around 15% of the cost and more than 4 times the attenuation of the conventional noise reduction measures.

How to select the optimum cooling tower noise control measures >

Axial extract fan silencing at source

4 large axial extract fans caused noise complaints over a wide area in Canada, despite multiple attempts at noise control based on conventional techniques. One email led to the noise being reduced by 99% with no site visits required - the whole project was completed over the internet.

Mitchell, the site engineer sent us an email with smartphone video clips and photos. Sound track analysis showed the problem to be high level tones at the 197Hz blade pass and harmonics. We used the photos to design retro-fit aerodynamic noise reducing components which the client made and installed to give 20dB attenuation at 100m.

"We are exceptionally happy with the overall results that were obtained, from a noise reduction, cost, and time stand point. INVC was very professional and prompt on all deliverables. Out of all solutions attempted this was by far the best and cost effective. The whole process was very smooth from first contact to installation … glad we went with INVC, thanks…"

In addition to the noise reduction, the performance of the fans was also improved which means that the project will pay for itself in reduced running costs.

Axial mine water spray fan noise attenuation

Proposed £100k conventional attenuators for 10 axial mine water evaporation fans in Australia would have had zero effect! A few emails and <£20k gave 23dB noise reduction and improved efficiency.

The mining company had a series of 10 large axial fans that are used to evaporate water pumped from underground. However, these had caused complaints over a very wide area. The quote for £100k of mufflers would have provided zero attenuation as they would be fitted only to outlets (half the noise is from the intakes) and they have virtually no attenuation at the dominant 200Hz tone. Our emailed details for aerodynamic modifications reduced the tonal content by 23dB at a cost of <£2k/fan. Fan efficiency was also improved…

Your problem may already be solved

Search our worldwide best practice options

Free Remote Diagnosis

Email us a video from your smartphone for an evaluation of best practice