Top 10 Noise Control Techniques

Vibration damping techniques

There are 2 basic techniques:-

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i) unconstrained layer damping where a layer of bitumastic (or rubber or similar) high damping material is stuck to the surface

ii) constrained layer damping where a laminate is constructed in situ – by far the better technique

Either re-manufacture steel (or aluminium) guards, panels or other components from commercially available sound damped steel or buy self-adhesive steel sheet from the supplier. The latter can simply be stuck on to existing flat components (inside or outside) covering c 80% of the flat surface area to give a 5 - 25dB(A) reduction in the noise radiated (use a thickness that is c 40% to 100% of the thickness of the panel to be treated).

Limitations

The efficiency falls off for thicker sheets. Above c 3mm sheet thickness it becomes increasingly difficult to achieve a substantial noise reduction.

Vibration damping examples

There are many successful applications in the food and pharmaceutical industries for noise control using high-performance damping (stainless sound deadened steel in particular as there are no hygiene implications for the treatment). Examples include weighing machine hoppers (10dB(A) noise reduction), vibratory feeders and conveyors (5 - 15dB(A) reductions) cowls and safety guards (3 - 9 dB(A) reductions) and complete close-fitting enclosures (e.g. homogenisers). In the case of vibratory separator noise reduction when grading confectionery, diagnosis showed that a major noise source was a large thin sheet distribution dome. Forming this component in stainless sound deadened steel contributed significantly to the overall noise reduction of 16dB(A) (from 105dB(A) down to 89dB(A)). Moreover, this modification could be incorporated into standard production machines at low cost.

Practical Design / Supplier

Constrained layer damping can be retro-fitted very easily for many applications. However, there are cases where some engineering development is required to get the most out of the technology e.g. building it into new or updated plant and machinery or combining with other noise control measures.

There are also design practices that should be used in forming, welding and in the choice of materials for more complex applications. Contact us for help in this area.

Supplier: SoundDampedSteel: www.sounddampedsteel.com +44 (0) 191 259

Manufacturer of a wide range of constrained layer damped galvanised steel, stainless steel, aluminium etc. Send drawings or templates for the damping areas and cut sheets can be supplied. Alternatively, you can buy complete sheets for local fabrication.

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Benefits

Low cost, large noise reductions, rugged.

Technique

Vibration isolation need not involve steel springs or rubber bushes. In many simple cases, mounting motors, pumps, gearboxes and other items of plant on rubber bonded cork (or similar) pads can be a very effective way to reduce the transmission of vibration and therefore noise radiated by the rest of the structure. This is particularly the case where vibrating units are bolted to steel supports or floors.

A high percentage of plant ostensibly “isolated” in this way is not actually isolated as the bolts short-circuit the flexibility provided by the pads. Any rigid connection across the pads will compromise the vibration isolation. In order for the vibration isolation pads to be effective, additional flexible elements (usually thinner layers of the same vibration isolation material) must be fitted under the bolt heads with load-spreading steel washers or plates as shown in the figure. Do not over-tighten the bolts, but make sure you use nyloc nuts or thread locking compound.

Limitations

Short-circuiting by bolts or other rigid connections is the most common issue. This approach does not generally reduce low frequency vibration significantly, but it is very effective at higher frequencies (above c 200Hz). If pumps, motors etc are bolted to steel plates, frames or tanks, then these behave as loudspeakers. The isolation prevents the transmission of the higher frequency vibration components, reducing the noise. However, if the source is bolted to the planet (e.g. concrete floor), then the isolation will not reduce the overall noise level – concrete floors only radiate low frequency sound.

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Whilst this approach relies on specialist knowledge for both the design of the modifications and the predictions of the attenuation, the knowledge that this award winning Quiet Fan Technology is available can not only dramatically reduce costs, but it can also reduce energy consumption.

Typical fan noise attenuation applications

Axial or centrifugal flow fans (from 10cm to 4m diameter).

Benefits

Low cost, rugged (no maintenance for the life of the fan), fast, hygienic. It often results in increased fan efficiency (10% - 25% improvement over conventional silencing) that can contribute towards net zero sustainability goals by reducing power consumption and therefore running costs.

Techniques

It is based on a similar approach to that used in Formula 1 where teams invest heavily in the design of aerodynamic aids to control the airflow round their cars. As fan noise is the sum of the turbulence generated pressure fluctuations in the air shed by the blades, we have developed a range of aerodynamic inserts that are installed inside the fan casing to smooth the flow. This reduces the pressure fluctuations – and hence the noise – at source without introducing the back-pressure often associated with silencers.

This not only reduces the tonal noise travelling down the intake and exhaust ductwork (typically by 10dB – 20dB), but also the noise passing through the fan casing. This may not only eliminate the need for silencers, but also the need for acoustic enclosures or lagging. In a significant proportion of cases, this approach can actually improve fan efficiency which means that it pays for itself in reduced running costs.

In addition, as the low frequency noise has been reduced at source, it is also often possible to insert low cost, purpose designed acoustic elements into existing ducts and stacks that provide a substantial reduction (10 – 30dB) in the broadband noise without affecting system efficiency.

Limitations

The amount of broadband attenuation that can be installed without fitting silencers depends on the local geometry of the system.

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Technique

Almost invariably it is possible to reduce pneumatic exhaust noise permanently by 10 - 30dB by fitting effective silencers. The following are the practical points that can make the difference between success and failure:-

back-pressure: for a well-designed silencer, the performance bottleneck is often the coupling – eliminated by fitting a larger coupling - and silencer

clogging: fit a straight-through absorptive silencer that cannot clog (and has no back pressure)

multiple exhausts: manifold the ports into a single, larger diameter pipe fitted with either a specialist straight-through silencer – or the rear silencer box from virtually any make of car (from your local “Quick-Fit”). Typically 25 – 35dB(A) reduction.

Limitations

None.

Download the Top 10 noise controls pdf with sound files here >

Suppliers: effective pneumatic exhaust silencers are available from:-

http://www.silvent.com/en-uk/products/?group=-safety-silencers

https://www.goodhanduk.co.uk/Catalogue/Exair-Air-Products/Air-Silencers/Straight-Through-Mufflers

http://www.servais.co.uk/products/silencers/sn112-medium-duty-absorptiv.pdf

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Technique

In most cases, it is possible to exchange existing nozzles (usually simple copper pipe tube outlets) for quiet, high efficiency entraining air nozzles. These will not only often reduce noise levels by 10dB(A) (or more), but they also use less compressed air (typically 20% less) for the same performance. Consequently, they pay for themselves quite quickly.

Also consider reducing the airline pressures wherever possible, running tests to determine the minimum pressure required for the job. This not only reduces the noise further, but it also reduces air consumption.

Limitations

Occasionally, space and performance requirements mean it is not practical to use an entraining nozzle.

Air lance nozzle change video example at https://youtu.be/9yzqaMHlvJ0

Download the Top 10 noise controls pdf with sound files here >

Suppliers: ranges of high efficiency nozzles are available from:-

If you want to learn more, please visit our website Noise Barrier Solution.

Featured content:
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Eco Benefits and Sustainability of FRP Grating

https://www.brauer.co.uk/airmiser-nozzles-s149.aspx

http://www.silvent.com/en-uk/products/

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Limitations

It is not always practical to implement the quieter options (space, power transmitted, temperature…).

Suppliers: low noise toothed belts are available from:-

http://www.cross-morse.co.uk/timing_belt2.asp

http://www.transdev.co.uk/pages/belts/eagle/eaglepd_advantages.htm

Most of the major suppliers have quieter versions of their drives, usually associated with higher quality and performance products.

Download the Top 10 noise controls pdf with sound files here >

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Limitations

This approach can take significant time (and some capital) to implement if the motors are replaced gradually – although more rapid implementation is possible where the new units reduce running costs.

However, we also have a standard modification design that can be retro-fitted to existing motors that typically reduces the noise by c 10dB(A). Contact us for more information.

Download the Top 10 noise controls pdf with sound files here >

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Technique

The existing guards on many machines can often be simply improved to provide a significant noise reduction. The two key principles involved are:-

i) Minimise gaps: halving the open area (“gaps”) in a set of guards will reduce the noise by c 3dB. If you can reduce the openings (flexible seals, additional close fitting panels etc) by 90%, then a 10 dB noise reduction is possible. The graph above shows the trade-off between open area and attenuation. If the guard is made from steel with a theoretical attenuation of 42dB (see example shown on graph), looking up the actual attenuation achieved in practice with a total gap or leak of 5% (for the guard) gives a figure of 13dB i.e. the maximum attenuation will be 13dB. If you reduce the total gap to 1%, then the attenuation increases to 20dB.

In practice, the modifications can range from covering the whole of a mesh guard with steel or polycarbonate sheet, fitting a “roof” over simple vertical guards or blocking relatively small leaks round the edges of quite close fitting guards with seals or rebates.

In cases where hygiene is an issue, there are high hygiene sealed absorbent materials available such as Hygiene Advance A from:-

Ecophon: +44 (0)

http://www.ecophon.com/uk/products/Modular-ceilings/Hygiene/Hygiene-Advance--A-C3/

Custom Audio Designs

http://www.customaudiodesigns.co.uk/

Limitations

The law of diminishing returns sets in once you have closed the largest gaps and leaks, so there is a limit to the attenuation that can be achieved. Visibility can also be an issue that limits the area of acoustic absorbent that can be included inside guards. However, we have developed and used a few innovations for this type of application – contact us to discuss particular issues.

Download the Top 10 noise controls pdf with sound files here >

Further Information and Resources

Technical support for all these techniques and further case studies are available from us. Feel free to contact us or call to discuss particular applications.

For more extensive noise problems across departments or whole sites – the next step is to...

Noise in industrial operations can be a challenging yet necessary issue that companies must address. The operations of a manufacturing plant, construction site, and similar environments tend to be very loud, and this noise pollution can extend to the surrounding companies and neighboring residential areas. Moreover, the ongoing loud noises can impact the health and productivity of the onsite workers.

To meet NIOSH and OSHA standards and regulations, businesses must use effective noise control solutions for industrial complexes and other production areas. These strategies have applications across manufacturing sites and industrial environments.

In this guide, we cover the nuances of noise control solutions adaptable to various industrial landscapes and manufacturing settings. We will also review the multiple challenges contractors, architects, engineers, and site managers face.  

Noise Control Challenges Across Industries

Every industry faces unique noise control challenges, from healthcare facilities to manufacturing plants. The key is to determine the specific challenges that you face and determine tailored solutions to mitigate against the industrial-level acoustic issues.

Here’s an overview of specific challenges faced by businesses in various industries and potential solutions that can help mitigate them:

Manufacturing Plants

Challenge: High decibel levels from machinery. Solution: Implement soundproofing measures, isolate noisy equipment, and consider investing in quieter technologies.

Data Centers

Challenge: Intense noise emanating from both backup power generation, and the large hvac equipment needed to cool the server rooms. Solution: Place sound-absorptive peripheral walls around the generators and hvac equipment.

Electrical Substations

Challenge: Transformers emanate low-mid range noises on a continual basis, affecting adjacent residences and businesses. Solution: Utilize attenuated transformer technology, and install sound-absorptive peripheral walls around the transformers.

Offices and Call Centers

Challenge: Open office layouts and constant communication. Solution: Integrate sound-absorbing panels in designated quiet zones and encourage additional ear protection.

Highways and Rail

Challenge: Increasing traffic volumes for both highway and transit rail is leading to elevated noise levels to adjacent communities. Solution: Build tailored sound barrier solutions, implement noise-reducing surfaces, and regulate vehicle speeds.

Battery Energy Storage Systems (BESS)

Challenge: Cooling equipment required to keep large battery banks from overheating. Solution: Utilize attenuated baffles around intake and exhaust outlets, and install sound-absorptive peripheral walls around the site.

Site managers across industries can tailor these solutions to address specific noise challenges, fostering a more tranquil and compliant working environment. Effective industrial noise control enhances employee well-being, increases productivity, and ensures regulatory compliance.

These solutions foster a safer and more comfortable working environment, reducing the risk of hearing damage and associated health issues. In addition, it improves community relations by reducing the impact of industrial activities on surrounding neighborhoods.

Selecting Appropriate Noise Control Solutions for Industrial Settings

Choosing the right noise control solutions for your industry requires carefully assessing the specific noise sources, environmental conditions, and regulatory requirements. Here’s a step-by-step guide to help you make informed decisions:

1. Conduct a Noise Assessment

The first step is to identify and quantify the noise sources in your facility. This includes machinery, equipment, processes, and other activities that generate noise. These assessments, or Noise Studies, are conducted by professional Acoustical Engineers who have the specialized skills and software programs required for this exercise.

Measure the noise levels using appropriate equipment to determine the frequency and intensity of the noise.  Determine the most effective mitigation treatments for the specific noise source and site conditions.

2. Understand Regulatory Requirements

Familiarize yourself with local, national, and industry-specific regulations regarding noise levels and exposure limits. Ensure compliance with these standards to avoid legal issues and potential fines.

3. Prioritize Noise Sources

Identify and prioritize the most significant noise sources based on their contribution to overall noise levels. Focus on addressing the most critical sources first.

4. Consider Engineering Controls

Explore engineering controls as a means of noise reduction. This may involve modifying machinery, processes, or equipment to reduce noise emissions. Examples include installing mufflers, isolating vibrating equipment, or using quieter technologies.

5. Evaluate Administrative Controls

Implement administrative controls, such as scheduling noisy activities during less sensitive times or rotating employees to limit their exposure to noisy environments.

6. Consider Acoustic Barriers and Enclosures

Install barriers or enclosures around noisy equipment to contain and redirect the noise away from sensitive areas. This can be particularly effective for outdoor machinery or industrial processes.

• Outdoor Noise Sources: Use reinforced noise barrier walls with aesthetics, strength, weatherproofing, and high-end noise reduction. Mobile noise barriers are compact, portable sound control option ideal for space-constrained sites. These barriers effectively reduce noise emissions, providing flexibility and ease of deployment in areas with limited space.
• Indoor Noise Sources: Use acoustical materials for walls, flooring and windows.
• High-Volume Applications: Certain solutions are best suited for high-volume situations where other solutions may not be applicable.

7. Evaluate Sound-absorptive Materials

Use sound-absorbing materials like panels, walls or baffles to reduce reverberation and control noise levels. These sound attenuation panels can be strategically placed where noise tends to bounce and amplify.

8. Consider Long-Term Maintenance

Evaluate the maintenance requirements of the chosen noise control solutions. Regular inspections and upkeep are essential to ensure continued effectiveness.

Periodically reassess the noise levels in your facility to ensure that the implemented solutions remain effective. Adjust as needed to address any changes in equipment, processes, or environmental conditions.

Are you interested in learning more about Noise Barrier? Contact us today to secure an expert consultation!

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