The recent increase in popularity of MUGAs across the country has led to a rise of noise-related issues associated with their use. There is little in the way of official guidance for the assessment of MUGA noise affecting nearby residents and so it is generally appropriate to employ a pragmatic, common sense approach to any assessment.

The following 5 noise mitigation strategies are commonly employed to control MUGA noise emissions and minimise the potential for complaints:

• 1. Distance

  The main and most obvious method of reducing the noise impact of MUGAs is to site them as far as possible from nearby residents. The closer MUGAs are to dwellings, the higher the likelihood of complaints. Fields in Trust’s document “Planning and Design for Outdoor Sport and Play” recommend that MUGAs are located a minimum of 30m from the nearest residential property wherever possible. Achieving this 30m is often difficult or not possible for many developments we work on in London and other built up areas where space is at a premium. In these cases, physical mitigation and careful management are key to ensuring acceptable noise levels are achieved.

• 2. Physical Mitigation

  There are a number of mitigation measures that can be built into the MUGA design in order to minimise noise generation or transmission to the nearby dwellings:

  • Where space allows, installing barriers and bunds between the MUGA and dwellings can significantly reduce noise emissions. It should be noted that in order for these barriers to be effective they need to cut the line of sight between the residents and people using the MUGA. This often requires the barriers to be at least 3m high. Barriers of this height can be quite imposing and in some cases it may be necessary to strike a balance between noise impact and visual amenity.
  • Noise from balls impacting the MUGA fencing can be a significant source of MUGA noise emissions. Wherever possible it is recommended that the panels are constructed of perforated sheet metal or weld mesh in place of a chain-link type fence in order to reduce rattle and ball impact noise. It is also important that anti-vibration (AV) bushings are used to fix the fence panels to the supports. These bushings acoustically dampen the panels and minimise structure-borne noise transmission, which has the effect of reducing the magnitude and duration of the impact noise.

• 3. Maintenance

  Poorly maintained MUGAs will generally generate significantly more noise than well maintained ones. This is due to a number of factors including damaged panels, loose brackets, worn AV bushings and squeaky gates.

• 4. Hours of Use

  Night-time use of MUGAs is significantly more likely to disturb nearby neighbours than use during the day. Where MUGAs are privately managed this is easily controlled however where MUGAs are intended for public use it can be difficult to ensure that they are only used during the intended hours. One method of naturally controlling hours is to limit artificial lighting, meaning that the MUGA is less likely to be used when it gets dark. However, this carries security risks and should be determined on a case-by-case basis.

• 5. Residents’ Engagement

  Where a new MUGA is proposed close to existing residential properties, a powerful method of reducing the potential noise impact on nearby residents is to ensure that the local community are engaged with the proposals as far as possible. This can be achieved by educating residents on the benefits of MUGAs, making them aware of plans at an early stage and, of course, ensuring that local residents have access to the MUGAs and a simple method of reporting misuse or damage.

We hope you find the above useful. Cass Allen has extensive experience in MUGA noise impact assessments and we have a detailed archive of MUGA noise data that can be used to help inform the design, placement and management of these important facilities. If you would like any further advice or help then please don’t hesitate to get in touch.

Councils in London and elsewhere are increasingly asking for detailed assessments of ground-borne noise where developments are located close to railways and other sources of vibration.

Ground or structure-borne noise is noise in the audible frequency range (approximately 20Hz – 16 KHz) than is transmitted as vibration and then reradiated into rooms as noise.

With railways, ground and structure-borne noise tends to be dominant at around 100Hz. This is perceived as a low frequency rumble as trains pass by. Most of us will have experienced this at one time or another when in a building near a railway.

For new residential developments, this rumble has the potential to disturb future occupants. Particularly during the night-time when residents will be most sensitive to noise.

Unfortunately, there are currently no UK or international standards for the assessment of ground-borne noise affecting new residential developments. The most relevant guidance is that given in the Association of Noise Consultants guideline – Measurement and assessment of ground-borne noise and vibration. The ANC guideline summarises current research and guidance from elsewhere.

One of the guidance documents referenced in the ANC guideline was published by the American Public Transit Association (APTA). This suggests criteria for acceptable maximum levels of ground-borne noise affecting various building types, including a criterion of 35 dB LAmax for ground-borne noise affecting residential properties. This criterion is increasingly being adopted (as 35 dB LASmax) by Councils when defining acceptable ground-borne noise levels for new developments.

In our view 35 dB LASmax represents a good standard but it may actually be acceptable for ground-borne noise levels to exceed this limit, depending on other factors such as the frequency of events (e.g. train passes) and the range of maximum noise levels that occur.

There are various treatments that can be adopted to reduce ground-borne noise affecting new developments. However, where significant ground-borne noise levels are present, full structural anti-vibration bearings are likely to be required. These are typically rubber or spring bearings that are used to isolate the building structure near ground level.

Spring bearing on a steel framed building

Elastomeric rubber bearing on steel framed building

Images provided by Mason UK (bearing manufacturer and supplier)

Such treatments carry significant cost, risk, design and program implications. It would not be unusual for the treatment of a medium sized block of apartments next to a railway in London to cost £100-150K in bearing costs alone. There is also the associated costs in design work, added costs to the structure and additional construction work onsite. Bearings also add complexity to the design that increases the risk of construction errors or timetabling issues. It is therefore important to ensure that bearing treatments are only used where strictly necessary.

Given the implications of such treatments, it is always advisable for developers to establish ground-borne noise levels and Council requirements early on where development sites are located near to railways or any other significant sources of vibration. In this way any required treatments can be assessed and properly costed and budgeted for.

Amendments made to The Town and County Planning (General Permitted Development) (England) Order 2015 will have a significant impact on how developers approach Class MA (office to residential) permitted developments.

In a move that was widely expected by many in the industry, The Permitted Development order has now made permanent the existing rights to convert existing offices buildings for residential use. However, an additional criterion has been added, stating that the Local Planning Authority (LPA) must consider the ‘Impacts of noise from commercial premises on the intended occupiers of the development’ when assessing applications. Previously this was not a consideration and there was no mechanism in place for LPAs to refuse applications on noise grounds.

The reason for this criterion is principally as a result of campaigns on behalf of licenced premises and two specific documents: the ‘London Grassroots Music Venues Rescue Plan’ and the ‘Bristol Live Music Census Report’. Both reports and the campaigns cite that the permitted conversion of offices into residential properties have resulted in noise sensitive receptors (i.e. residents) being introduced into areas where there are long established music venues or other sources of noise. This, in turn, has given rise to noise complaints from the new residents and the LPA imposing additional constraints on the music venue or noise source. This is seen as unfair and a potential threat to the night time economy of the UK.

Although the requirement to assess noise impact has been welcomed by campaigners, this move falls short of the ‘Agent of Change’ principle which had been campaigned for. The agent of change principle seeks to place the responsibility for noise mitigation measures on the incoming noise sensitive use, not the premises generating the noise.

It should be noted that although the wording of the amendment does not oblige the LPA to apply the Agent for Change principle, it does not preclude it either. The lack of clarity has been highlighted in a recent debate in the House of Lords in which ministers were called upon to provide further guidance. It will be interesting to see what further information is provided in the coming months.

The discussion surrounding noise and permitted developments touches on a wide range of legal and ethical questions, and the answers may not be as straightforward as they seem.

Given the lack of clarity in the guidance, it is advisable for developers to contact the Local Authority prior to submitting a Class MA permitted development application to fully understand their requirements with respect to noise.

If you have an upcoming Class MA permitted development application and you are concerned about these recent changes to legislation, please contact us.

In spite of the obvious benefits of keeping dwellings well away from industrial uses, increasing pressure on land and the drive for more housing has meant that residential development close to industrial uses is becoming ever more common.

Local planning authorities (LPAs) often resist such schemes on noise grounds. Their argument being that the legal onus (under the Environmental Protection Act 1990 (EPA)) would be on the industrial use to reduce noise should future residents complain about industrial noise once they have moved in. This can place unreasonable constraints and/or financial burdens on industry and in some cases has resulted in closure and the loss of employment.

However, more recently there have been signs from government that residents moving into developments near industrial uses may be expected to accept that some noise is inevitable. This is reflected in the softening of planning guidance regarding the definition of what constitutes a statutory nuisance, which in effect, reduces the requirement for local authorities to take legal action under the EPA (see http://planningguidance.communities.gov.uk/blog/guidance/noise/noise-guidance/ para 007).

Moving in the opposite direction, a recently revised British Standard (BS4142:2014) has, for the first time, required that an assessment be made on dwellings proposed near existing industrial uses. The problem with BS4142 is that it only assesses noise external to a proposed dwelling and therefore does not take into account any mitigation that can be incorporated into the façade (eg high performance glazing or mechanical ventilation etc). As a result, most proposed dwellings proposed near industrial uses will fail to achieve a satisfactory BS4142 rating, which provides support for any LPA wishing to refuse such an application.

Our experience is that a reasonable compromise can often be negotiated with LPAs based on a combination of layout/landscaping together with façade mitigation designed to ensure that internal noise levels achieve suitable standards (typically as set out in BS8233:2014). Typical mitigation strategies are briefly discussed below:

1) Site layout

Whilst it is good practice to keep dwellings as far as possible from the boundary with an industrial site, noise does not reduce quickly with increasing distance. It is therefore normally not practical to rely on distance alone to reduce the industrial noise. However, all else being equal, placing playgrounds or public amenity land on the boundary is beneficial acoustically, especially when incorporating an appropriately designed acoustic barrier/bund on the boundary line.

Of potentially more benefit, is locating terraced houses or flats on the boundary to act as an acoustic barrier for the rest of the site. This requires careful façade and amenity space design but can help to maximise land usage.

2) Landscaping

It is a common misconception that trees/bushes act as acoustic barriers. In fact, bands of trees/bushes up to around 25m deep have no significant acoustic properties. However, the visual screening they provide can often help residents to believe that the noise is less and so they do have a psychological value. An effective acoustic barrier needs to be imperforate and of sufficient surface mass so that the sound travelling through it is insignificant compared with the sound travelling over the top (typically a minimum surface mass of 10-12kg/m2 is required). Tall wooden barriers can be effective but can also be visually dominating. Earth bunds are very effective, but can take up too much space, and so a small bund combined with a smaller wooden barrier on top is often adopted.

3) Façade design

The weakest parts acoustically of a typical dwelling are the glazing and the ventilation. Both of these can generally be specified to achieve whatever is required to achieve satisfactory internal noise levels. Typically a noise survey will be carried out to quantify the industrial noise and then the glazing and ventilation will be specified accordingly. Matters can be complicated by solar gain and overheating issues, but our experience is that façade design is normally fairly straightforward.

4) Negotiation with the industrial user

Often it is tempting to try and reduce the noise at source through negotiation with the industrial user. Whilst this can be effective, especially if the noise is caused by a well-defined source that is readily mitigated or replaced (eg an old compressor or fan, where replacement would be much cheaper than noise control to the residential scheme and where the prospect of new machinery would be a tempting incentive for the industrial user to co-operate). However, for large industrial sites that contain many noise sources or where the noise source is not immediately apparent (eg noise breakout through large industrial sheds) our experience is that mitigating the industrial noise is often problematic both technically and in terms of logistics. Clients also are legitimately concerned than once they become dependent upon the industrial user their negotiating position becomes weaker.

As with many aspects of acoustics, early integration of an acoustician into the planning team is essential when considering a residential development near an existing industrial use. 

 

 

It’s a quirky English phenomenon that, during advert breaks for Coronation Street or Eastenders, a large proportion of the country decides to make a cup of tea.

It’s a race against time – you have around 3 minutes to boil the kettle, suitably stew the tea bag, add the milk (do you take sugar?) and get back to the settee in time to ensure you don’t miss the next plot twist.

Kettle manufacturers are conscious of this predicament, with kettles being designed to boil water as quickly as possible. Most UK kettles draw 3Kw, which is at the limit of what domestic plugs can handle and roughly the electricity generated by 21m² solar panels in full sunlight.

With approximately 1.5-1.75 million kettles being boiled during any single advert break – this needs a lot of power!

This puts a huge and sudden demand on the national power grid that the larger power stations can sometimes struggle to meet. In fact, national grid employees watch TV to help them prepare for the surges as best they can, as shown in this recent documentary.

To help solve this problem at a local level, a number of smaller and more reactive biodiesel and gas power generation sites are increasingly being installed around the country. These facilities can ramp up quickly as required to support the power supply in a given area; a flexible solution to a very British problem!

One potential drawback of these systems is the noise output from their generators – which can be significant. Careful acoustic design and planning is therefore crucial to ensure that nearby residents are not disturbed and applications for new sites run smoothly.

Based on our experience, we have put together a list of factors that are important in the successful implementation of these sites.

1. Location

   Urban and rural sites present different challenges. Background noise levels tend to be higher in urban areas than in rural areas, which means that the noise from the generators will be less audible in urban areas.  However, it is likely that people will be living closer to the generators. Conversely, rural generator sites tend to be situated farther from residents, but background noise levels can be extremely low meaning that generator noise can be heard over a larger distance.

   The generators should always be placed as far as possible from residents; however other noise mitigation strategies are often also helpful.

2. Barriers

   Acoustic fences or bunds can be effective in reducing noise from the site. In general terms, the closer and higher the barrier is to the equipment, the more effective it will be. Additionally the design of the barrier (e.g. surface mass, number of gaps etc.) will also play a large part in the overall effectiveness.

3. Selection of Units

   It is recognised by the industry that the generators can be noisy. As such it is common for manufacturers to provide ‘low noise’ models or acoustic enclosures. Our experience is that, wherever feasible, this should be allowed for at the outset of the project given the nature of the noise and typical locations of the sites.

   Additionally, the more detailed the noise data provided by the manufacturers, the more accurate acoustic calculations can be. With detailed noise data we are able to carry out a value engineering exercise and explore using fewer or smaller barriers for example, whereas this may not be possible with only basic noise data.

4. Local Planning Authority Consultation

   Typically, the generators run sporadically and for only short periods. As such, stringent mechanical plant noise limits, which would be appropriate for more constantly running plant, are often not applicable for these sites. This means that design targets may potentially be relaxed, which would reduce the amount of physical noise mitigation required. It is important that the LPA are consulted as early as possible by a competent acoustician to negotiate the possibility of a relaxation to the design targets.

   Through appropriate calculations and 3D noise modelling, Cass Allen are able to advise on the feasibility of new schemes, optimise site layouts and design the size and location of noise barriers and other mitigation measures where required. In this way, we can help keep the noise impact of your cup of tea to a minimum.

It is becoming increasingly common for ‘screening rooms’ to be incorporated into developments to maximise their appeal.  With the recent debacle at this year’s Oscars, we thought it would be an appropriate time to offer some pointers on how to avoid other cinema-based blunders.

We have recently assessed the design of screening rooms in a range of developments including:

• Residential led mixed-use
• Hotels
• Care homes

In all of the above there are a number of common issues that should be considered as early as possible in the design stages to minimise the noise impact of the screening room on surrounding residents:

Location

Clearly, the further the screening room can be placed from residential rooms (or other potentially noise sensitive areas) the better. Ideally, there should be a ‘buffer’ of at least one non-habitable room between the screening room and any nearby residential room.

Partition Design

Where it is not possible to have buffer rooms then the next consideration will be to ensure that the partitions separating the two uses provide an adequate level of sound insulation.

It is typical for screening rooms to have loud sound systems installed.  Whilst that is great for the people watching the film, controlling noise (particularly low-frequency music or dramatic rumbles) is challenging in areas with limited space.

In general, the following design features should be adopted for all partitions separating screening rooms from adjacent apartments:

• Independent internal linings – wherever practical, the ceilings, floors and walls of the screening room should be completely independent or ‘acoustically isolated’ from the surrounding structure in order to avoid direct sound paths into adjacent residences.
• Deeper cavities and fibrous insulation – where cavities are formed in walls, floors and ceilings these should be made as wide/deep as possible. The deeper the cavity the more effective that partition will be at controlling low-frequency noise. There should also be at least 50mm of fibrous insulation in any cavity to further improve the acoustic performance.
• High mass layers – the partitions should be constructed from the heaviest materials practicable (i.e. multiple layers of dense plasterboard or dense concrete blockwork).

Where screening rooms are located close to residential areas, very high-performance partitions will be required and these can have significant implications on layouts, the structure and cost.

Hours of Use

Even with careful physical design and placement of the screening room, it will generally be necessary to limit the hours that the room can be used. Unlimited use of the screening room can quickly lead to complaints from residents, particularly at night when general background noise is lowest and people are more sensitive to noise.

Noise Limiters

It is possible to install noise level limiting equipment into screening room sound systems. This will stop users from turning the volume up beyond a pre-determined level, which will depend on the design and location of the room. This level should be set once all partitions and sound systems have been installed, and permanently adhered to thereafter.

Given the multiple issues involved in installing a screening room in a residential development, we would recommend seeking advice at an early stage from an acoustician with relevant experience.

Please get in touch if you would like any further information or have an upcoming project that you require specific guidance for.

Curtain walling is used on many of the larger residential developments we are involved in due to the construction and cost benefits.

The main acoustic issue with curtain walling is the potential for flanking sound transmission via the junction with separating walls and floors.

The type and design of curtain walling can vary significantly, however there are a few key elements required to ensure that sufficient sound insulation levels are achieved.

Please see below our top 5 details to watch out for.

 

1) Single mullions or transoms

In order to achieve high levels of sound insulation (e.g. between two adjacent residential units), at least two transoms will be required across separating floors, and two mullions will be required across separating walls. Where only one mullion or transom is provided, this will significantly reduce the achievable performance.

Example of single and double transoms at separating floor

2) Continuous mullions or transoms

Mullions or transoms can transmit noise along a façade very effectively, significantly limiting the achievable sound insulation. It is, therefore important to break mullions and transoms across separating floors and walls using flexible gaskets and to ensure there are no rigid fixings between them (including connecting brackets etc). Mullion or transom inserts may also be required where higher sound insulation levels are targeted.

Example of mullion & transom detailing at slab edge (section view)

3) Inadequate fire stopping across separating floors

Fire stops can be very helpful in providing acoustic insulation and often perform this dual role. To achieve high sound insulation levels across separating floors, the fire stopping should make an airtight seal between the slab edge and the façade as shown below. Fire stopping is typically formed from dense mineral wool and it’s important that it does not come loose overtime or as the building settles. Some products are better than others in this regard.

Good fire stopping is essential to acoustic performance

4) Noise ingress via spandrel panels

Spandrel panels in curtain walling are often formed of thermal insulation, sandwiched between two thin layers of aluminium. These panels provide very little airborne sound insulation and therefore can be an acoustic weak point in the façade, resulting in unacceptably high internal noise levels in developments located in noisier areas. It is normally straightforward to specify the build-up of spandrel panels once a survey has revealed the external noise levels that they need to deal with.

Noise ingress via spandrel panels

5) No ceilings

In all the examples so far, the ceiling is important in achieving higher sound insulation levels. In many developments we work on, commercial units or ancillary areas are located below residential units and do not have ceilings. In these cases, it is prudent to box in the slab edge detail as below. This treatment can also be adopted in addition to a ceiling if higher levels of sound insulation are sought, or to reduce noise ingress via spandrel panels.

Boxing in where no ceilings are proposed

The above list is not exhaustive and every project is different, however we hope it helps give you a flavour of the types of details to look out for. Sound insulation issues can have significant ramifications if not identified quickly and therefore should be considered early on in the design, particularly with regards to the setting out of mullions and transoms.

If you are working on a development with curtain walling and you are concerned about noise ingress or noise transfer we would be happy to help.

Noise barriers, or acoustic screens, are commonly used to reduce the effect of noise from roads, rail and industrial sources on residential properties. In particular, they are often required by local authorities to achieve recommended noise levels in external areas, including gardens and communal amenity spaces.

In order for noise barriers to be effective, they should achieve the following criteria:

• Barriers must be generally imperforate. Hit and miss fencing, slatted fencing or foliage are not effective noise barriers as sound passes through the gaps.
• Barriers should have a minimum mass of 10 kg/m2. Noise may pass through lighter weight materials.

For masses above 10kg/m2, the sound reduction provided by a noise barrier is unlikely to improve. The performance will be limited by sound diffraction over the top of the barrier. Therefore, a 10kg/m2 close-boarded timber fence will normally provide the same noise reduction as a 100mm concrete wall. Be careful if suppliers are recommending heavier noise barrier options for acoustic reasons, as these reasons may be false. Call us for an impartial view.

Set out below are common architectural screening options with comments on their acoustic effectiveness. It should be noted that, although some options will provide limited reduction in actual sound levels, any sort of visual screening has been shown to provide a subjective acoustic benefit – people are less bothered by a noise source that they cannot see!

Combinations of different barrier types are often also used for aesthetic or practical reasons. For example, an acoustic fence could be used on top of an earth bund where there was a requirement for a very high barrier (this is a particularly cost-effective option for sites where there is a lot of earth spoil which would otherwise have to be transported off site), or a green screen could be used in front of a brick wall for a more attractive aesthetic.

Cass Allen are experienced in the design and specification of noise barriers. Please let us know if you would like more information.

This month we were kindly invited to Paragon Interiors Group’s annual golf day at The Nottinghamshire Golf and Country Club and we thought it would be a bit of fun to run a competition to find out who could hit their ball the loudest.

A sound level meter was set up on the course to measure the maximum noise level during competitors’ drives at a distance of approximately 1m.

It was a very wet day, but despite the rain, there was no shortage of competitors to take on the challenge. Some interesting tactics were employed, with golfers selecting specific clubs and balls to try and make the loudest sound possible.

The worthy winner of the competition was Sam Wynn from Pulse Associates with a drive measuring a whopping 108 dBA. For reference, 108 dBA is about the same noise level you would hear during a sonic boom. Sam won himself a nice pair of Sony Wireless Headphones.

The full results of the measurements are shown below. There was a large variation in the measured levels with an average of around 97 dBA.

We found that the type of club and the strength of the shot were big factors in the measured noise level. The highest measured levels tended to also be very clean, powerful shots, although a few mishits also recorded very high levels!

Think you can hit a louder shot? Let us know when your next corporate golf day is and we will happily come along to find out!

The guide is aimed at developers and architects and sets out common reverberation control treatment options for rooms.

These treatments are used to prevent excessive reverberation and are often required to achieve acoustic specifications or regulations. In particular, reverberation treatments are required for the following development types:

• corridors in residential developments to comply with Building Regulations Part E
• teaching rooms in schools to comply with BB93 (as required by Building Regulations Part E)
• rooms within medical or healthcare facilities to comply with HTM08-01
• office workspaces (particularly open-plan workspaces) to achieve good quality work environments

The amount and type of treatment will vary depending on the size and use of the room. In many cases, the location of the material is also very important.

The performance of acoustic treatments is graded based on the amount of sound they absorb. The best absorbers are Class A (almost total absorption), however, Class B & C absorbers are also very effective.

Set out below are a number of common treatments along with their pros and cons.

Other treatments

As shown above, there are various treatment types, many of which also come in different styles and configurations. The key is finding the right treatment (or combination of treatments) for every project. Cass Allen has extensive experience in the design and specification of reverberation treatments including numerous products and suppliers. Please let us know if you would like more information.