The building is made up of three spaces. The main event space is the 21-metre high warehouse, which can be split into two. It is complemented by the hall, a 1,603-seat auditorium with a flexible stage, while a seven-storey tower at the back of the warehouse provides green rooms, dressing rooms and office space.

The building’s façades, of concrete and corrugated metal, contrast with the refurbished brick warehouses and newly built flats, offices, and television studios that make up the new St John’s neighbourhood.

Building services and lighting design had the challenge of responding to the multiple uses of the building while maintaining an industrial aesthetic.

Gas boilers are used for heating currently, but the building is designed to connect into the future St John’s heat network. The hall and warehouse are air cooled and heated, while the tower and social rooms’ loads are met with local emitters. Chillers provide cooling.

Close collaboration between BDP’s electrical, mechanical, lighting and digital engineers was essential because of the complex nature of the internal building geometry, and a BIM model was created to coordinate services.

The BIM model showing the three building elements

The lighting team worked closely with architect OMA and interior designer Brinkworth to coordinate lighting concepts. The result is a combination of general, architectural, experiential, complex emergency, and technical theatrical lighting systems, threaded through the internal building geometry. Three bespoke luminaire types that worked with the contemporary façade design were developed with Stoane Lighting and Zumtobel. In total, 164 luminaire types were used throughout the building.

The energy model demanded >100lm ·W^-1, a significantly higher requirement than that in Part L, which was 60lm ·W^-1 at the time of design in 2018; in the 2021 revision it is 95lm·W^-1. Illumination criteria for general and emergency lighting was determined using the Technical standards for places of entertainment 2015 – The association of British theatre technicians in combination with the usual CIBSE and British Standards. 

The warehouse has capacity for up to 5,000 people standing, and can be divided by a movable, full-height acoustic wall. The hall has a flexible stage that can house an audience of up to 1,600 seated or 2,000 standing. The warehouse and the hall can work together, allowing the stage to extend to a depth of 45 metres. The lighting includes house lighting, management lighting, high output working light, technical space task lighting, and back-of-house blue lighting.

House lighting was provided by ETC ArcSystem luminaire types. These warm white digital multiplex (DMX) fittings mounted to the technical grid allow super low-end DMX dimming to achieve 0.2 lux management light levels. High-output working light illumination of >600 lux was provided by 58,000lm downlights from Glamox. 

In areas where people are working without windows, a 5,000K correlated colour temperature (CCT) has been selected to increase the perception of brightness. Technical spaces use a combination of >500 lux white-light illumination and a blue lighting system for access during a performance. 

Underneath the auditorium

The hall is a traditional raked theatre with removable seating. A range of luminaire types was integrated into the interior architecture to celebrate and delineate the internal geometry, and contribute to house lighting levels. Details include a balcony shadow gap, in-floor uplights, skirt detailing, and uplighting to the soffit from the technical grid edge. A bespoke luminaire was developed to illuminate stair treads. The restricted floor buildup of the auditorium did not allow for a more traditional step-tread lighting solution, so a free-standing, floor-mounted step light was developed that could be installed in the voids below seating.

The warehouse is designed to be a blank canvas. Vertical DMX colour-change linear luminaires around the perimeter can support events with a full-scale lit feature. The general and emergency lighting arrangement allows for cellularisation of the space for set building and isolated space uses.

The tower has multi-level mixed-use spaces connected to the warehouse and includes offices for Manchester International Festival, the green room, and dressing rooms. Most of these spaces have no ceilings and exposed services, so a trunking system was used to minimise ‘visual clutter’. The trunking houses pre-wired power and data, reducing the requirement for secondary containment, making it time- and cost-effective. A range of luminaire types can be inserted, including standalone emergency modules.

Danny Boyle’s version of The Matrix launched the venue last autumn

The main foyer has multiple uses, which is reflected by the lighting. The design responds to the brick arches of the 19th-century railway line that forms part of the foyer. A mixture of adjustable cool-white wide-beam and warm-white narrow-beam track spots are used to create day and evening scenes, combined with uplighting on brick facades.

Integral lighting was used for bar fronts and shelving, and lighting was integrated into the stair handrails, providing localised illumination to the steps, reducing shadowing, and adding a sense of drama. The handrails also provide high-risk emergency lighting. That the building contains very few windows has been used to its advantage by the team, which has harnessed the transformative quality of light to create a variety of scenes and evoke different atmospheres for day and night. 

Outside the building footprint, in the public realm, an undercroft is illuminated with levels suitable for pedestrians and cyclists, ranging from 15 lux to 250 lux, appropriate for daytime and night-time use. 

The design of the services prioritises flexibility, responding to each individual performance and accommodating shows with diverse sets. 

Electrical infrastructure

The electrical infrastructure divides into two systems: house services and a dedicated performance system. This segregation prevents any interference, and handles uneven load distribution. A network of busbars and tap-offs feeds into multi-outlet power panels, complemented by fixed outlets distributed throughout.

A room in the tower

The building boasts an extensive stage lighting and audio visual (SLAV) system, interconnecting outlet panels to form a robust network. A centralised control system oversees this network, employing various AV and data cabling types to match the different shows and setups. 

Strategically placed outlets and power panels in every part of the performance electrical system offer flexibility for main and breakout productions. This, combined with SLAV outlet panels, allows for dynamic show configurations. An advanced performance lighting control system, connected to a central hub, governs performance and house lighting, offering flexible control.

Ventilation and acoustics

A top-down supply ventilation strategy, using swirl jet diffusers, was adopted for the theatre and warehouse to maintain flexibility without introducing physical constraints. To address potential noise challenges, careful diffuser selection was crucial.

Rather than applying a uniform building service noise criterion, specific criteria were established for each event scenario, allowing for more relaxed standards where higher building service noise levels were acceptable. This flexibility matched the requirement for events that needed increased airflow rates, such as high-capacity concerts.

A section view showing the interconnection between the Hall and the Warehouse

Building physics modelling was employed to manage potential noise concerns during heating. This verified that when the hall and warehouse were pre-heated before a show (when higher service noise levels were acceptable) temperatures could be maintained during performances. 

Aviva Studios is an exciting new addition to Manchester’s vibrant cultural scene and the innovative building services engineering and bespoke design allow the operator to create a myriad of performance spaces that put visiting artists in the best possible light. 

• Steve Merridew is a building services engineering director and Nick Meddows is senior lighting designer at BDP

The post Setting the scene: Manchester’s new arts venue Aviva Studios appeared first on CIBSE Journal.

Most people have personal experience of annoying noise from mechanical ventilation systems, which causes them to turn it down or off. In older, less airtight houses, there is likely to be sufficient ventilation from infiltration to avoid really poor indoor air quality. In modern, airtight houses, however, occupants rely on the effective operation of their ventilation systems to enable good indoor air quality.

The research for our 2019 article, ‘How loud is too loud: noise from domestic mechanical ventilation systems’,² in the International Journal of Ventilation, was issued with the consultation,³ and reinforces the risks that excessive noise causes for occupants. So how does the consultation draft AD-F help prevent this unintended adverse consequence? (See panel ‘AD F consultation draft wording’). For one thing, it omits the line that indicates noise is not controlled under the Building Regulations – but how does it propose to control noise in the future?

Bizarre issues

The current proposal in the draft AD F (see panel) is entirely inadequate to address noise from mechanical systems. There are no objective standards to meet and, rather bizarrely, the issues highlighted in paragraph 1.5 don’t mention noise from the fan. Why use terms such as ‘minimise noise’ and ‘not unduly noisy’, rather than state objective noise levels that we can measure?

Also surprisingly, reference is made to taking account of outside noise when considering the suitability of opening windows for purge ventilation. Is this purge ventilation, as described in AD F, to rapidly dilute pollutants and/or water vapour? From an acoustic perspective, there would be few concerns about external noise ingress when using it in this way. The more common use of purge ventilation is to mitigate overheating, but that is a separate issue.

Why does this draft talk about ‘sizing and jointing ducts correctly’, rather than simply stating noise criteria to be achieved? If noise is controlled under the Building Regulations, contractors will quickly find out how to make sure their designs and installations work. The Building Control body can check or ask for third-party verification; measurements of noise levels can easily be made if there is any doubt about whether they comply with the criteria.

Need for regulation

The necessity to include noise from ventilation systems within the Building Regulations is evident to stop occupants suffering poor indoor environmental quality (IEQ) as a result of intolerable noise. There needs to be:

• Performance standards for sound from ventilation systems
• Demonstration of compliance at the design stage
• Demonstration of compliance on completion.

We suggest the minimum performance standard to prevent most people being annoyed is:

Whole dwelling ventilation: sound from any type of mechanical ventilation system – when measured according to BS EN ISO 16032 – should not exceed:

• 26 dB LAeq, T in bedrooms, and
• 30 dB LAeq, T living rooms.

Extract ventilation: sound from any type of mechanical ventilation system – when measured according to BS EN ISO 16032 – should not exceed:

• 26 dB LAeq, T in bedrooms, and
• 35 dB LAeq, T  in living rooms, and
• 45 dB LAeq, T in kitchens, sanitary accommodation and bathrooms.

The requirement relating to whole-dwelling ventilation should include sound from mechanical extract ventilation (MEV) and mechanical ventilation with heat recovery (MVHR) systems. The one relating to extract ventilation should include intermittent extract fans used with natural ventilation, as well as MEV and MVHR systems. The performance requirement should apply with all doors (and windows) closed, and be adopted for the measurements. Although recirculating kitchen canopies do not provide ventilation, they should meet the same noise standards.

Design-stage compliance

Manufacturers, generally, have sound data for their products, but quote the values in different and often confusing ways – for example, quoting levels at 3m in the freefield, which may be 18dB lower than the level the same product makes in a small room.

It would be useful to have a consistent approach to describing sound levels, so designers can compare products, and building control bodies can determine compliance. For extract fans that are ‘in the room’, for example, describe the standardised sound level in a room of 15m³, to represent the probable worst-case condition of a small room.

For MVHR systems, duct length and bends reduce the transmitted sound. A calculation can be given for a particular dwelling based on the ductwork layout and the source sound power level at the calculated operating point. Manufacturers or system designers can provide these calculations; manufacturers currently propose the operation point of their equipment, so this calculation could be added to that or determined from the proposed ductwork layout.

Demonstrating compliance at completion

Commissioning measurements of sound should be taken at the same time as those for ventilation airflow. All data should be lodged online, in a database linked to the SAP and Energy Performance Certificate, along with the airtightness test result and other evidence of compliance.

A less onerous regime could give building control bodies the power to demand commissioning sound measurements be carried out by a suitably qualified person if they have any concerns over the sound levels, based on an aural assessment.

Responses to the Approved Document F consultation must be received by 7 February 2020. The government needs our opinions. Let’s not waste this opportunity to help it make appropriate regulations that protect people.

References:

1. Building Regulations: Approved Documents L and F (consultation version).
2. How loud is too loud? Noise from domestic mechanical ventilation systems, International Journal of Ventilation.
3. Ventilation and indoor air quality in new homes, Ministry of Housing, Communities & Local Government.

Jack Harvie-Clark is founder of Apex Acoustics

The post Loud and clear on noise control appeared first on CIBSE Journal.

For those designing naturally ventilated buildings, noise mapping is an important resource. The external noise determines what level of acoustic performance is required in a vented façade to achieve an acceptable internal noise level for occupants. The higher the external noise level, the harder the façade has to work for the same (specified) internal noise level. So it is easier to naturally ventilate buildings on quieter sites. Likewise, if the performance of the façade is enhanced, the external noise levels can be higher for the same internal noise level.

It can be demonstrated, using the noise map, that 20% more land area would be available for naturally ventilated buildings with an increase of 5dB in the acoustic performance of vented façades. This figure comes from an estimation that all noise levels within an urban area are below 65dBA; 80% < 60dBA; 60% < 55 dBA; 40% < 50dBA and 20 < 45dBA.3

Figure 1:Relationship between heat gain and acoustic performance: openable window and alternating baffle

With most new developments built in densely populated, noisy areas, there is an increasing need for improved acoustic performance. Acoustic ventilation comes at a cost, however, and – if it’s too high – energy-consuming mechanical ventilation may be specified instead, to maintain comfortable internal temperatures and prevent overheating. So if windows are still to be used as the main source of ventilation control, buildings with high external noise will require more creative solutions.

Small openings have higher levels of sound reduction than larger ones, but also offer reduced levels of ventilation. To overcome this paradox, this article argues that the acoustics and ventilation requirements should be considered in tandem when designing buildings. It also looks at solutions to restrict noise while ensuring adequate ventilation.

Figure 2: Relationship between heat gain and acoustic performance: Fully baffled window and more glazing transmits

Ventilation and acoustic performance
As well as there being a link between the open area of a vent and its acoustic performance, the line of sight through a window affects sound reduction. A fully open sash window, for example, will give less acoustic resistance than a side-hung window. Further benefits can be gained by turning the window away from the noise source, or by using a window with a ‘dog leg’ arrangement.

Napier University carried out research on the acoustic performance of different window types.1 In 425 tests covering 14 open window types, it found that – depending on the window type and the angle of sound to it – the open windows achieved a sound reduction of 15dB to 24dB for an open area of 0.2m2. Smaller openings achieved a sound reduction measurement of between 18dB and 26dB.

Most consultants assume a window only gives 10-15dB of sound reduction. By focusing on open areas and the line of sight to the noise source, however, it is possible to optimise window selection and opening sizes to minimise solar gain and achieve sound reductions of between 15dB and 26dB. Using Napier and Defra’s data, this approach can be said to increase the chances of using natural ventilation on noisy sites by around 40%.

Various methods to improve acoustic performance while meeting ventilation requirements are discussed below, and there is an explanation of how the modelling of sound can accurately predict the effectiveness of sound-reduction methods.

No shading – high internal noise levels

Some shading – reduced internal noise levels

Increased solar shading – internal noise level compliant.

Figure 3: Solar shading reducing heat gains and subsequent open area of the window – and, thereby, noise levels in classrooms.

Ventilation efficiency as a form of noise control
The flow across a vent is fixed by ventilation rates needed to offset building heat gains. Openings can be decreased in size, however, if there is a higher air pressure, because additional airflow will be forced through. A smaller vent will, of course, have an inherently higher acoustic performance. In practice, cross and stack ventilation make better use of temperature differences across vents because of air buoyancy, which increases the pressure across vents and so draws higher flow rates. Along with fan-assisted ventilation, they can be seen as a type of noise control, therefore, as smaller openings in windows are needed compared with single-sided ventilation, which has lower pressure across vents.

Site and building orientation – heat and acoustic gains
It is common to do an orientation heat impact assessment during the early design stages of a building. Typically, south-facing windows have higher heat gains, so are harder to acoustically attenuate than north-facing ones – with lower heat gains – because larger vent sizes are required to offsite heat gains.

In the same way, noise levels (acoustic gains) to façades vary depending on whether they have direct line of sight to a noise source or whether they are in acoustic ‘shadows’.

Enhancing g-values and the acoustics of windows
A g-value of 1 represents full transmittance of solar radiation, while 0 represents a window with no solar energy transmittance. In practice, most g-values will range between 0.2 and 0.7, with solar-control glazing having a g-value of less than 0.5. Put another way, the g-value times the area of the glass, plus solar orientation, are key factors affecting the total heat gain upon a space.

So the g-value is critical when considering a building’s heat gain and its acoustic design; lower heat gains mean smaller openings, with inherently higher levels of acoustic resistance, can be used to ventilate spaces. It is worth considering the g-value as a form of noise control, therefore. Figure 1 and 2 shows how window designs that reduce heat gain have a better acoustic performance. Thermal mass and solar shading can also be used as an effective form of noise control, as shading/cooling reduces either the heat gains or the ventilation to offset these heat gains (see Figure 3). So these design options should be considered when buildings are on noisy sites.

Side hung with no acoustic barrier

Audio visualisation of window opening

Sound reduction with acoustic barrier positioned at window opening.

Stills from audio visualisation representing the passage of sound through a range of window types at Wadham College, Oxford

Acoustic shading
In the same way that light shadows can be used to reduce heat gains, acoustic ‘shadows’ can be used to control noise ingress. Acoustic shadows are more complex than light ones as the wavelength of sound is massive compared with that of light. This means sound tends to bend around objects, reducing the effectiveness of an acoustic shadow.

A second challenge with using acoustic shadows lies in modelling and estimating the performance of external fins, barriers, balconies, box windows, sound-absorbing bricks and other external acoustic devices.

The effects of acoustic shading from balconies are presented in ISO 12354-3:2017 Part 3, Airborne sound insulation against outdoor sound, which suggests that balconies can offer up to 7dB of additional attenuation to that of windows. IES software can then be used to assess the shading effects of these enhance the building’s acoustics.

The Hong Kong Housing Authority, in conjunction with researchers, is using mock-up roadside flats to design/incorporate acoustic windows and acoustic-shading fins, to mitigate the impact of traffic noise on affordable housing developments, while still allowing passive air circulation. A range of mitigation options are now being used at King Tai Court, close to Prince Edward Road East, a major east-west thoroughfare in San Po Kong.

Building shaping
Individually designed floorplans and acoustic buffers (circulation spaces, staircases, service facilities, lifts) are often used as a form of noise control. Taking this one step further, building shaping is now being developed to mitigate acoustics and thermal gains. At Tak Pui House, part of Tak Long Estate, in Hong Kong, steps, deep reveals and star-shaped building forms are being used to reduce noise ingress into large-scale housing developments.

Visualising the passage of sound
Research by Mach Acoustics, with the universities of Southampton and Bath, has led to a new idea being developed, whereby the visualisation of sound is used to show how it flows through openings placed within the façade of a building. This visualisation, along with acoustics and CFD modelling, can be used to design new window forms/shapes that offer significantly enhanced levels of acoustic performance, while still allowing the flow of air through passive buildings.

This process is undertaken on the principle that one can see, understand and so optimise the passage of air and sound through open windows. For example, acoustic screens have been modelled for Wadham College, Oxford, so that the design team can see how and why different arrangements achieve different levels of acoustic performance. (See this YouTube film for a noise simulation on different window types over time, and this article on the web for a visualisation that compares the passage of sound through different types of windows.)

Visualising building shaping

The use of sound visualisation has proved to be a useful tool in understanding how a building’s form can be used to optimise its acoustics and thermal performance. Here, an acoustic fin has been extended beyond the building’s fabric to protect a key façade containing open windows, thereby offering acoustic protection to this opening.

Summary
Pressure increases across vents – achieved by selecting cross- stack or assisted ventilation – will result in smaller opening vent sizes and, therefore, enhanced acoustic performance.

Reduced solar gains are also important because lower heat gains require lower airflow rates; this means that smaller openings with higher levels of acoustic resistance can be used. Heat gains can be reduced by means of building orientation, solar shading, balconies, acoustic fins and undulating façades. As in the case of solar gains, acoustic gains are important to consider. Solar gains increase when the building is pointed at the sun. Similarly, façades exposed to or facing noise sources will experience higher exposure to acoustic gains. So it is critical to consider both  elements/assessments in tandem.

Finally, the use of visualisation, modern types of modelling and early testing has demonstrated that it is possible to create options that will ensure windows will still be used to provide ventilation controls to today’s modern, low carbon buildings.

Visualising building shaping
The use of sound visualisation has proved to be a useful tool in understanding how a building’s form can be used to optimise its acoustics and thermal performance.
Here, an acoustic fin has been extended beyond the building’s fabric to protect a key façade containing open windows, thereby offering acoustic protection to this opening.

■ Ze Nunes is the founder of Mach Acoustics

References:
1 Open data: strategic noise mapping, Defra, 2012
2 England Noise Map Viewer, Extrium
3 The future of windows, pp36, Apple Books

The post How audio visualisation can drive the natural ventilation of buildings appeared first on CIBSE Journal.

The foundation even took the design team, assembled to build the new facility, to Denmark to visit two schools that had been designed around a similar ethos, with open-plan learning to encourage pupil and staff interaction.

Avanti Architects’ design for Trumpington Community College incorporates elements from the Danish schools, including a day-lit atrium; the school’s entrance leads pupils directly into this triple-height space, the centrepiece of which is what the architect terms an ‘over-sized’ stair. This doubles as informal raked seating, while leading pupils up to two L-shaped teaching floors that wrap around the central void.

The upper floors have classrooms at the outer perimeter while open-plan, informal teaching areas surround the atrium, to enable up to 250 students to be taught informally, at small tables, in clusters of two and three.

Sound absorption is integrated into the materials selected by the architect. Credit: Jack Hobhouse

The school wanted open-plan spaces to facilitate multiple, simultaneous activities – but open-plan teaching has a bad reputation for noise issues. Max Fordham, the acoustic consultant for the project, was so concerned that background noise levels would significantly affect speech intelligibility that it used its SoundSpace laboratory to replicate – for the design team and teaching staff – the precise acoustic conditions that pupils would experience. It then used the laboratory to develop an appropriate solution.

‘Our brief was to create comfortable study conditions in which students and teachers could communicate over short distances of up to approximately two metres,’ explains Pedro Novo, acoustic engineer at Max Fordham. He says there are two main acoustic issues with open-plan space: control of direct sound coming from adjacent spaces and control of the reverberant sound, which arrives from all directions. ‘Because the open-plan spaces are high, long and wide, these conditions occur in pretty much every space where teaching will take place,’ he adds.

The performance standard for speech intelligibility in open-plan spaces is described by the Speech Transmission Index (STI), which Max Fordham used as the main acoustic design parameter for the open-plan spaces. It applies to speech transmitted from teacher to student, student to teacher, and student to student.

The design aim was to achieve a high STI up to 2 metres from the source (for example, a teacher’s voice) and a low STI at higher distances – 4 metres and above – to minimise disruption to neighbouring spaces. ‘An important aspect of the Index is the background noise – which will change with the number of students and activities in the space – because the higher the background noise, the lower the speech intelligibility,’ says Novo.

Trumpington College Credit: Jack Hobhouse

An activity plan, developed with the school, was used to establish the likely overall noise level resulting from teaching and pupils’ activities in the open-plan space. Max Fordham used its computer prediction model (see panel, ‘Sound advice’) to calculate the STI, using the overall level of noise as the background noise level. It then used the SoundSpace to convey to the staff and project team the noise and speech intelligibility that would be experienced by the pupils.

After experiencing the noise environment virtually, in the auralisation demonstrations, it was clear that some form of acoustic treatment was required if the open-plan spaces were to be used effectively. To reduce the reverberation time, Max Fordham worked with Avanti Architects to add sound-absorbing materials to them.

‘Having acoustic absorption installed near to noise sources is more effective than having the absorption installed far away, so that the noise is readily absorbed, rather than being allowed to bounce back and forth between surfaces,’ says Novo.

Max Fordham calculated that a minimum 2,000m² of acoustic absorption was required to absorb as much sound as possible and prevent noise buildup, while physical barriers were needed between adjacent working areas. ‘Avanti Architects were extremely accommodating and creative in integrating this vast amount of acoustic absorption, and in designing 1.6m-high storage spaces between working areas,’ says Novo.

A variety of acoustic-absorption measures were adopted. On the walls, some spaces are fitted with timber battens, behind which is 50mm of mineral wool. On other walls, metal mesh retains the mineral wool. Perforated plasterboard is employed in the corridors and on the ceilings, behind which is also mineral wool. ‘Acoustic absorption results in reduced general noise levels, which, in turn, results in people speaking at lower sound levels – so there is a positive feedback loop when acoustic absorption is applied,’ says Novo.

Max Fordham's SoundSpace converts into a meeting room when not being used for acoustic demonstrations

Max Fordham also looked to the two Danish schools that had so impressed the foundation for acoustic-treatment design precedents. It found that their interiors incorporated acoustic wall and ceiling panels, and sound-absorbing treatment on the floor; however; it also recognised that the occupancy density is much lower in the two Danish schools, with each pupil having an average 9m² of floor space. In UK schools, the figure is closer to one pupil every 3m², so the acoustic treatments at Trumpington would need to work much harder than those in the schools in Denmark.

Using SoundSpace, various demonstrations were undertaken at different points of the design to show the effectiveness of the diverse acoustic solutions as they were developed. For example, Max Fordham used a demonstration to illustrate intelligibility at different distances. ‘The review made clear that effective communication would be possible up to a maximum of 2 metres,’ says Novo.

SoundSpace was also employed to show staff the effect of different occupancy levels, and their acoustic impact on pupils in the open-plan space if only 50% – or only 25% – of the recommended sound absorption was installed. ‘The auralisation enabled the school to understood the importance of the acoustic treatment in enabling the effective use of the open-plan spaces,’ says Novo.

In fact, the SoundSpace demonstrations were integral to convincing the client of the importance of acoustic absorption, which spared it from being reduced as part of a value-engineering exercise. Novo adds: ‘The school is extremely pleased with the result, which allows them to undertake the activities that they have envisaged for the open-plan space, while creating an overall comfortable acoustic environment.’ 

Trumpington College SketchUp drawing

The post Silent treatment: acoustic design in an open plan school appeared first on CIBSE Journal.

The design process is not helped by the fact that indoor air quality, thermal comfort and acoustic comfort are often considered independently, sometimes by different design consultants.

To address this issue, the Association of Noise Consultants (ANC) has produced a guidance document entitled Acoustics, Ventilation and Overheating – Residential Design Guidance or the AVO Guide.  A draft version was released in February for consultation. The consultation is open until 11 May and views on the draft can be submitted via the online questionnaire.

The AVO Guide seeks to encourage a design and assessment process that recognises the interdependence of acoustics, ventilation and overheating. It includes the following elements:

■ An explanation of ventilation requirements described in Approved Document Part F (ADF)

■ An explanation of the overheating assessment methodology described in CIBSE TM59

■ Acoustic guidance relating to the different ventilation and overheating conditions

■ A worked example, including indicative design solutions.

The key issue for the acoustic guidance is that it suggests different (elevated) noise levels for the overheating condition relative to those for the ADF ventilation condition. The reason for this is that the overheating condition occurs for only part of the time and occupants may accept a trade-off between acoustic and thermal conditions. 

The contribution to internal noise levels from external transport sources and mechanical services are considered separately and independently because there is evidence that occupants have a different tolerance for each.

For external transport sources, the AVO guidance for the overheating condition suggests risk categories based on the resultant internal noise level. The risk categories are summarised in Table 1.

Suggested risk categories based on the resultant internal noise level

In the daytime, the ‘high risk’ category results if internal levels exceed 50dBA, on the basis that speech communication will be significantly affected. At night, the ‘high risk’ category relates to the World Health Organization Night Noise Guidelines level for which ‘adverse health effects occur frequently and a sizeable proportion of the population is highly annoyed and sleep-disturbed’. 

However, it is important to note that the values presented in the table should not be regarded as fixed thresholds and the risk of an adverse effect occurring will also depend on how frequently, and for what duration, the mitigation of overheating is likely to result in increased internal noise levels.

For mechanical services, it is suggested that the internal ambient noise levels given in Table 1.5 of CIBSE Guide A should be achieved for ADF extract ventilation conditions. For the overheating condition, reference is made to the additional guidance in Section 1.10.10 of CIBSE Guide A, which states that a range of +/-5dB on the Table 1.5 values may be acceptable, depending on the particular situation. 

The mechanical services noise targets for the overheating condition are based on systems operated to meet the overheating criterion (such as TM59).  It may be acceptable for systems to have a boost mode (included for occasional use with louder fan noise) provided that this does not form part of the strategy for meeting the overheating criterion and is under
occupant control.   

The AVO Guide suggests that testing should be undertaken to confirm that the installed mechanical services meet the target noise levels. The intention is to avoid the situation where installed services are considered too noisy by occupants and therefore not used appropriately.

The worked example sets out the typical design process in terms of:

• The activities that would be undertaken by the acoustic consultant
• The information that the acoustic consultant should be supplying to the other members of the design team (for example, locations where simple opening windows are not likely to be a viable means for controlling overheating)
• The information that the acoustic consultant may need from other members of the design team in order to make their assessment (for example, the area of façade openings and the number of hours that they are required to be open to meet the overheating criterion).

The guide aims to promote a collaborative design process with good communication and timely coordination between the different disciplines. This is hopefully consistent with the integrated design approach advocated by the recently released CIBSE TM60 Good practice in the design of homes. It is acknowledged that on challenging sites, it may be necessary to develop the design iteratively to arrive at a scheme that best addresses acoustics, ventilation and overheating.

To assist designers and environmental health officers, the worked example gives guidance about approximate external noise limits for which each of the Part F template ventilation systems would be appropriate. Similarly, the guide gives examples of passive ventilation solutions that offer a higher level of sound insulation than simple opening windows. These include the use of balconies/winter gardens, attenuated windows and acoustic louvres.

Given that environmental design and building services are so integral to the AVO guidance, the authors would appreciate any feedback from CIBSE members through the online questionnaire.

■ Dr Anthony Chilton  is a senior partner at buildling services engineers Max Fordham. He says his goal is to find acoustic solutions that help make buildings more comfortable.

The post Sound advice – taking external noise into account when ventilating buildings appeared first on CIBSE Journal.

Since launching its SoundLab almost 20 years ago, Arup has used the technology to simulate room acoustics, allowing clients to hear and compare sound at different points of a hall or theatre. Cundall, meanwhile, has added another dimension to sound modelling – 3D graphics – after the introduction of its Virtual Acoustic Reality (VAR) last year.

By combining a virtual reality (VR) headset with a gaming engine and audio files, Cundall takes clients on an immersive audio and visual tour of a building before it is built. Being able to hear how sound changes as they move through different spaces ensures decisions – for example, on internal finishes – are based on experiential factors, rather than numbers on a page.

SoundLab

Arup created its SoundLab in the early 2000s and now has 11 worldwide. The tool allows consultants to ‘listen’ to buildings before they are built, and dispense with technical jargon and complex reports. The process, called auralisation, is the acoustic equivalent of a visual rendering in architecture.

As well as performing-arts spaces, SoundLab is used to demonstrate acoustic conditions in schools, offices and residential buildings; for determining glazing configurations; in railway stations – for example, to test announcement systems’ clarity; and for demonstrating environmental noise from infrastructure systems, such as high-speed rail, aviation and highways.

For room acoustics in an existing space, consultants visit the space and measure the impulse response. This is the reaction of the room to an impulse, such as a balloon bursting, a handclap or – more commonly – electronic signals generated by loudspeakers. The recording of the response creates a unique fingerprint for a specific space that is driven by: the geometry of the room; the relationship between the source and the receiver; and the room materials.

Ned Crowe, senior engineer at Arup, says: ‘The first sound that travels from the source to the receiver is the direct sound and – shortly after – you’ll have a reflection of the sound from the floor, walls and ceiling all arriving at different times, different intensities and from different directions.’

Next comes a process of convolution, which combines the impulse response with an anechoic recording – a ‘dry’ sound recorded in the absence of any reflections. The resulting sound can be played back in the SoundLab – an array of loudspeakers, set out in a sphere around the listening position, that reproduces the exact timing, strength and direction of the reflections as you would experience them in the room. ‘You get to listen to what that anechoic recording would sound like inside that particular room,’ says Crowe.

Any aspect of the performance-space design – its shape, form, geometry or materials – can be modified, while the receiver can be moved to the stalls, balcony or box, allowing the client to listen to the acoustic differences at any musician or audience location.

‘The real value in the SoundLab is that it allows the client to listen to the differences,’ says Crowe. ‘We tend to develop a number of options so that if, for example, there is a discussion about cost associated with the height of the ceiling, we could model both options and allow the client to make an informed decision about what the differences would be.’

Virtual acoustic reality

Cundall has taken its acoustic modelling a step further by adding 3D graphics. Its VAR technology links graphics program Unity with an Oculus Rift VR headset and CATT Acoustic software, allowing clients to immerse themselves fully within a virtual model. Here, they can walk around the building and listen to the audio signal change.

Synchronicity is the key to its success, says Andy Parkin, head of global acoustics at Cundall. ‘If any aspect is out of sync, the whole experience is ruined, because any lag between the user moving their head and the image moving can create motion sickness.’

Cundall’s Andy Parkin using the firm’s VAR

Cundall VAR maps out the virtual space with a grid of auralisations – so, as the user passes through the space, they go through different auralisation zones. Using an Xbox controller to navigate around a 3D representation of the building, the operator can listen to how the space sounds relative to their location, and assess sound clarity and the reverberation effects.

Although current computing power does not allow instant calculation of new scenarios, the virtual environments and acoustic models are pre-programmed, so comparative scenarios can be run.

Parkin says the technology has been most useful in the design of lecture theatres, because it lets consultants manipulate internal finishes and ‘value engineer’: ‘While a teacher is talking at the front, you can walk around and ensure the expensive acoustic finishes are applied only in the learning spaces, rather than in the periphery and non-learning areas, where clarity is not an issue,’ he says.

It also works the other way round. ‘If the finishes in the architect’s model do not work, we would be able to justify to the client why they need to spend more money on acoustic treatments,’ says Parkin.

Future trends

Oculus Rift now allows multiple sound sources to be projected into the model. ‘That’s taken it beyond a lecture-theatre scenario and into a retail mall or open-plan office, where you can model speech privacy and the distraction efficiency of surrounding speech,’ says Parkin.

Cundall’s latest project, for the Retail Expo in Olympia in May, involves modelling sound in two shopping mall atria – one with hard finishes and the other with acoustic treatment – allowing users to walk between them and assess sound-quality changes and acoustic comfort.

Cundall used VAR to value engineer acoustic finishes at a University of Birmingham lecture theatre

Parkin says: ‘Retail developers are taking sound a lot more seriously because, in a retail environment, it’s all about the time people spend in the space. There is the realisation that if we can make retail environments more pleasant, people will stay longer and are likely to spend more money.’

He adds: ‘People are getting the fact that, by spending money on the initial design, the return on investment can stack manyfold.’

Cundall is looking at VR in several contexts, including ways the auditory experience can be combined with more information from other design disciplines. ‘There are many different types of modelling software – Revit for building services and Dialux for lighting; what we’re trying to find is a common platform that can link all of these models together, until we have realised a fully immersive space.’

Parkin says VR companies, games designers and manufacturers are all working on the missing link and trying to reach a solution from different angles. ‘At some point we will have that ‘eureka’ moment.’

The post Hearing is believing – acoustic modelling technology appeared first on CIBSE Journal.

The guide summarises some of the main problems that can arise from heating, ventilation and air conditioning (HVAC) systems, and gives an overview of the frequency characteristics of the main noise sources, before describing the various sound transmission paths to receivers and how they may be controlled. This is followed by a detailed description of the various noise sources arising from building services provision: fans; variable air volume (VAV) systems; grilles and diffusers; roof-top units; fan coil units; chillers, compressors and condensers; pumps, motors and standby generators; boilers; chilled ceilings (active and passive); cooling towers; and lifts and escalators.

Detailed information about noise-emission data – enabling typical values of sound pressure and sound power levels to be estimated – is given in this section. This information will be of use to the designer in the early stages of design, before manufacturers’ test-based data is used in the final design stage.

There are further sections on:

• Noise control in plantrooms
• Mechanisms of airflow-generated – or regenerated – noise in ducts
• Prediction and control of noise transmission in ducts and fittings
• Predicting and controlling sound levels in rooms, and the effects on speech interference and privacy
• Noise transmission to/from outside in naturally ventilated buildings
• Criteria for the assessment of noise in building services systems
• Worked examples of the prediction of noise levels within rooms and at external receptors
• Fundamentals of vibration, vibration control and practical aspects of vibration isolation.

Noise from waterflow systems

Although much of the CIBSE guide deals with noise from HVAC systems, section 4.3.19 addresses noise from waterflow systems, including all water-supply and wastewater systems.

Pipework and components in waterflow systems radiate airborne noise, which must be considered. However, noise can also be radiated by building elements – for example walls and floors – because these services are structurally attached to them.

This applies not only to appliances, such as pumps and cisterns, but also to pipework. So the type of pipework can be important, as can considering whether equipment appliances and pipework should be isolated from the building structure. Noise in waterflow systems may be minimised by: good choice of equipment and pipework; careful installation to ensure smooth water flow; avoidance of excessive flow velocities; isolation to prevent excitation of the building structure; and good equipment maintenance (see panel, ‘Minimising noise in waterflow systems’). 

Noise from chillers

Chillers produce tonal and broadband noise. The evaporator and condenser elements of chillers usually display different acoustic characteristics. Noise from the evaporator is often composed of tonal noise, typical of that from rotating or reciprocating machinery, linked to the rotational frequency. Broadband noise is also present, generated by either liquid or gas-fluid flow. The tonal noise tends to be dominant – perceived as a whine or whirr – but the frequency range depends on the mode of operation.

Noise from the condenser is usually broadband and dominated by fan noise, although variable-speed fans do much to control the impact of this when the equipment is not operating at full load.

Air-cooled chillers combine these sources in a single unit, enabling bespoke noise-control packages of different sizes to be considered, depending on the acoustic attenuation required. Locating the evaporator in a plantroom will remove this external noise source and, usually, reduce the noise emission from the chiller’s external elements.

Ultra low-sound chillers

Acoustic attenuation towers being installed for Berkeley Homes

Cool-Therm has supplied an ultra low-sound, 1.8MW air conditioning package for a Westminster Berkeley Homes residential apartment development. It worked with M&E contractor Briggs and Forrester on a new design for the Turbomiser chillers to achieve the space and sound goals for Cleland House and Abell House.

Aecom’s sound specification required a limit of 51dBA at 10m. In standard format, the chillers were rated at 63dBA at 10m. To achieve the 12dBA reduction, the design had to be re-engineered, and acoustic attenuation towers were added to both sides of each condenser fan, making an upper array of 16 towers per chiller. Measuring 1.6m high and 1m in diameter, each tower is lined with lead-damping material and a perforated liner to absorb sound. The condenser fan is positioned at the midpoint, providing attenuation at both the air inlet and discharge sides.

A bull-nosed column in the tower further reduces turbulence, while sickle-bladed, low-noise fans help streamline airflow. The compressors are housed in acoustic enclosures, reducing sound from this source by 6-7dBA. Finally, refrigerant discharge lines from compressors to condenser are lined with lead insulation, further reducing vibration.

Guide B4 gives example noise levels from different types of chillers, although use of manufacturers’ noise-level data – based on standard test procedures – is always preferred.

The document concludes with a summary of the guidance on noise and vibration, eight appendices, a glossary of terms, and a list of reference material.

Minimising noise in waterflow systems

Acoustic measurements are taken using acceleration sensors at Geberit’s laboratory

The best way to reduce structure-borne noise is to stop vibrations from occurring in the first place, through holistic design and using ‘quiet’ appliances and pipework.

Jonathan Briafield, Geberit’s product manager for piping systems, says building acoustics has to be considered at the design stage to ensure bathrooms are located above other bathrooms or kitchens, rather than bedrooms and other noise-sensitive areas.

It is also critical to consider the location of appliances within the installation room. Wall-mounted toilets and washbasins are more acoustically beneficial than floor-standing equivalents because their frames are fixed to the structure of the building, while noise-reducing studs can further minimise noise transmission into the frame.

A rubber or foam seal between the toilet and wall can also reduce the transmission of vibrations from a flush or a dropped toilet seat.

Pipe materials should be considered too. Cast iron is best at reducing airborne noise, and many ‘silent’ pipes have made their way onto the market, says Briafield.

‘But cast iron pipes are very expensive, have a big environmental impact in production, and the rigid bracketing that fixes them to buildings can also transmit vibration into the structure,’ he adds.

Where vertical stacks are impossible, designers should minimise pipe offset angles – where noise is amplified – as well as use rubber-buffering and rubber-lined bracketry on pipes to alleviate vibration transmission.

‘To reduce noise throughout sanitary systems, the important thing is to study every aspect of the “noise chain” and reduce sound all the way through,’ says Briafield.

He adds that if designers use all of the above mechanisms, they can get noise levels down to 25dB in bedrooms – which is much lower than the UK benchmark level of 45dB in living rooms.

• Bob Peters is principal consultant at Applied Acoustic Design and chair of the Guide B4 steering committee
• Guide B is available to download at the Knowledge Portal

The post Peace of mind – CIBSE Guide B4 appeared first on CIBSE Journal.

The building, located on the historic Queens Terrace, will offer a range of practice, rehearsal and teaching spaces, a dedicated rehearsal and performance studio, plus a recording suite and library. It is hoped the project will be completed in 2018.

With experience of working on the Stowe Music School, in Buckinghamshire – among other music venues – a team of acousticians and building services engineers from WSP Parsons Brinckerhoff has been selected to design St Andrews’ music centre.

The auditorium

Stowe Music School, completed in 2013, is a purpose-built, two-storey facility comprising a 250-seater recital hall, a recording studio, 24 practice rooms, two classrooms and a soundproofed percussion room.

James Healey, acoustics associate director at WSP Parsons Brinckerhoff, says it is important in recital halls that the audience receives the direct sound produced on stage. To deliver this, large, high-level reflectors were placed above the stage at Stowe to angle the sound towards the audience.

Fixed seats in Stowe hall are acoustically absorptive

‘We also wanted to deliver the very early reflections from the sidewalls and ceiling,’ he says. ‘Acoustic diffusers were installed on the walls, close to the stage, to scatter the sound and avoid undesirable reflections.’ In addition, acoustic absorption was used either side and behind the seating area to ensure the audience does not hear any reflected ‘late sound’. This can come slightly after direct sound, affecting the audience’s perception of the performance.

ISO 3382–1:2009 Acoustics – Measurement of room acoustic parameters provides some guidance on performance spaces but, generally, the acoustic criteria is based on the team’s experiences. ‘It’s also dependent on the client’s aspirations – how they are going to use the space and what will be performed in there,’ says Healey. At Stowe, the hall was to be used mostly as a piano-recital space, which needed a controlled environment. This was achieved by providing carefully-modelled fixed acoustic conditions. ‘It’s important to ensure the sound stays the same, regardless of occupancy,’ adds Healey. ‘In recital halls with fixed seating, the seats have to have the same absorption qualities as people, so you get a standard uniform sound even if it’s unoccupied. At Stowe recital hall, the seats were of equal acoustic absorbance to that of a person so the conditions were balanced regardless of whether the hall was occupied or not.’

In contrast, the recital hall at St Andrews – which must offer a rehearsal space for orchestras and choirs – will require variable acoustic conditions,’ says Healey.

Different surface treatments and building materials have a bearing on sound quality. One of the challenges when designing the Stowe recital hall was that the ceiling had to be lowered to free up space in the ceiling void for the services systems. This meant changing the acoustic treatment within the space. ‘We made the ceiling heavier and changed the wall profiling, to stop the sound escaping through the fabric,’ says Healey. ‘We wanted to keep the low-frequency (bass) sound within the space because it offers warmth to the listeners by giving them a sense of being enveloped by it. If the materials are light, and there’s a lot of absorption or leakage of bass sounds, you get a cold sound that isn’t in keeping with the musical production.’

Services strategy

Graeme Bruce, WSP Parsons Brinckerhoff’s head of building services in Scotland, says acoustics criteria must be at the forefront of the HVAC services design at St Andrews: ‘The air distribution system must be carefully designed so it does not ruin the acoustic performance of the space.’

The ventilation strategy is particularly crucial to the success of the building, adds Bruce. ‘In rehearsal spaces, for example, we have to ensure outside noise doesn’t encroach into the space, and we don’t want noise escaping and becoming a nuisance to neighbours.’

The clean lines of Stowe Music School's exterior

External environmental factors in St Andrews will also be taken into account during design. Humidity control will be crucial for this coastal town, which frequently experiences fog and mist. ‘Imagine a November evening,’ says Bruce. ‘It’s pouring with rain outside and 200 people are coming into the auditorium. Because air humidity affects how sound travels, the system we design will maintain a constant condition, regardless of the external environment. Our design must deal with a variety of changing conditions.’

Also high on the list of considerations is the vibration through the building structure. Plant items – such as fans or air handling units (AHUs) – can send vibrations through a steel frame creating unwanted noise.

From a building services perspective, the most crucial element of the St Andrews project will be identifying the noise criteria to which the services strategy will have to be designed.

‘At the same time, we have to comply with Section 6 of the Scottish Building Standards, and achieve Breeam Excellent and EPC A ratings. All these are factored into the design process,’ says Bruce. ‘We have to ensure the acoustics team is aware of our thought processes at every stage, including plant selection and plant location.’

Sound modelling

The acoustics team at WSP Parsons Brinckerhoff uses modelling software to create a 3D representation of the space, within which any sound can be modelled in any location. ‘We can take Mozart’s recital and predict how it would sound in different points in the hall, and play it back to the client,’ says Healey. ‘That level of feedback is very important for something like acoustics, where what we’re creating is not visible.’

Angled walls stop 'flutter echoes' when recording

During objective analysis, the client is able not only to visualise the space using the architect’s 3D model, but also to hear how it’s going to sound. The acousticians work with a combination of models; they use the architect’s 3D design for visual cues, and develop their own acoustic model for importing and modelling the sound.

Recording spaces

The architectural detailing and building services design in the recording rooms at Stowe Music School will inform the design at St Andrews. At Stowe, each room has a dedicated AHU that enables a high level of sound insulation between rooms and avoids ‘crosstalk’ issues – when sound travels through common ductwork between different rooms.

In smaller rooms, such as recording studios, standing waves – or ‘flutter echoes’, when sound bounces backwards and forwards within a room – can occur if walls are positioned directly opposite one another.  ‘These unwanted effects have to be removed because you want as clean and pure a sound as possible in a recording studio,’ says Healey.

To overcome this at Stowe, the team angled the walls. ‘Having a slight angle on opposing surfaces eliminates those echoes. We apply this to all music-related buildings,’ says Healey.

Bruce adds: ‘One of the benefits of a multidisciplinary approach is that we work in a collaborative manner. This enables us to share information – and make decisions – quickly, which is important because projects usually run quite tight. It also ensures we can deliver – and exceed – the client’s brief.’

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