Acoustic input at design stage benefits site waste management plan

Eco Buildings
Contributing to a site waste management plan at the design stage results in quantified reductions in waste arising. This is achieved by evaluating recycled content and specifying building materials containing higher recycled content as well as reused materials.

MACH sees waste as careless, unsustainable and economically costly.  If we did not have ears, partition thickness, slab depth, glass thickness, doors, etc. could be made considerably lighter, meaning that less material would be required to build a building.  As such, within building design there is a balance between the materials needed for a high acoustic performance, and the reduced mass for a low energy, cost effective design. It is therefore critical to ensure that the correct performance standards and design strategies are used to make sure that the right acoustic performance standard is achieved without over specifying in order to minimise waste and embodied energy.

Often, acoustic treatment forms an integral part of the important architectural appearance of a building. It is often the case that over design occurs. However, MACH always looks to minimize waste by investigating a wide range of products and materials and carrying early reverberation time testing which allows us provide very accurate area of treatment and eliminate over specification. 
The roof to Eden’s Educational Building is formed from a timber structure. Thermal insulation made from recycled newspaper was used to provide the thermal insulation. To achieve the acoustic requirements of the exhibition space the plywood sheet used for lateral bracing was perforated to 20% open area. This principle has been used across a range of schools, higher education buildings and other MACH projects.
Acoustic input at design stage benefits site waste management plan

Pulling the wool over BREEAM

Acoustic Design, BREEAM
We believe in low carbon buildings and the typical 3 and 4 credits allocated purely to acoustics by BREEAM can be more or less guaranteed to help achieve the highest possible rating.

MACH differs from other consultants in our approach to achieving the energy usage credits, and credits relating to sustainable recycled materials. We aim to lead in the acoustics design of green buildings, investing over 7% of our turnover into research and by collaborating with leading universities. Our research focuses on reducing the energy usage of buildings as well as material selection. Acoustics is not often linked with these subjects, however naturally ventilated and hybrid buildings often suffer from noise break-in and high levels of sound transfer and occupancy noise issues. Focussing on these subjects means that MACH has and can develop a wide range of solutions to overcome the exceptional challenges in low carbon buildings.


Material selection and reducing the level of embodied energy – sheeps wool used in thermafleece is often a preferred option 

Pulling the wool over BREEAM

Open Plan – front loading for optimized results

Open Plan, Open Plan Spaces, Open Plan Teaching

MACH Acoustics is distinctive in our constructive design approach to open plan learning and educational building design. We work closely with the client from an early stage to ensure we are optimising the space with an accurate understanding of the end user needs. 
MACH Acoustics rely on extensive acoustic modelling to analyse and optimise open plan spaces. These models analyse:
·         Expected reverberation times
·         Speech intelligibility levels
·         Noise propagation throughout the space and the effectiveness of screens

Open Plan - front loading for optimized results
 
Furniture layouts can then be altered and the areas of treatment moved to optimise the space acoustically to ensure every aspect of the design of the space is working in unison to optimise the acoustic conditions. 
Auralisations are also often produced. This is a powerful tool that enables MACH to fully communicate to the client what the space will sound like and to compare the effects of different proposals. This ensures that MACH Acoustics proposed targets meet the client’s expectations.

MACH Acoustics have visited several completed projects to gain a deeper understanding of what the end users feel works well and what needs more work to ensure we are constantly improving our approach with open plan design in educational buildings.
This results in truly flexible, amazing, learning spaces that meet the client’s expectations.
Open Plan - front loading for optimized results

 

A Sound Education – Denbigh visit

Acoustic Design

A Sound Education - Denbigh visit

 A Sound Education 

The government’s new BB93 – Acoustic Design Standards for Schools, was launched just prior to Christmas! Shane Cryer of Saint-Gobain Ecophon, in conjunction with SCALA (Society for Construction and Architecture in Local Authorities) has arranged a series of roadshows atinteresting education projects around the UK, to explain the changes.

The first visit took place in Denbigh, at the striking Denbigh Welsh speaking primary school, YsgolTwm O’ R Nant. It was designed in-house at Denbighshire County Council, built by Wynne Construction (Richard Partington, 3rd from left) with the acoustic installation by M G Ceilings (Craig Russel, 3rd from right). David Whieldon, the project architect at Denbighshire County Council provided the concept:“YsgolTwmo’r Nant is a Welsh medium primary school in Denbigh, North Wales. ‘Ysgol’ means school and Twmo’r Nant was the pen name of Welsh dramatist and poet Thomas Edwards who plied his trade locally in the 18th Century.

Demand for Welsh medium education is still strong in Denbighshire and it was determined that YsgolTwmo’r Nant need to be refurbished and extended to meet the demands of BB99 for a school with 280 full time pupils. “There was a very effective collaboration of ideas and solutions, involving all parties, including Denbighshire CC, ourselves, M G Ceilings (our subcontractor) and Ecophon, to ensure that the high quality of finish and specification was achieved”.

 MACH Acoustics’ Ze Nunes will feature in “Local Authority Building & Maintenance” as they intend to lead with it in their annual “schools transition” edition in March! With shrinking budgets, primary school halls are almost always multi-use. It is therefore no longer acceptable to design them with long reverberation times.The standards for sports halls have changed; guidance notes to follow (from the Association of Noise Consultants) will give further instruction regarding the positioning of acoustic absorbers to eliminate flutter echo.

Areas of concern

In MACH Acoustics view, BB93 2014 is a significant improvement over the old BB93, providing clearer and possibly more appropriate performance standards.

 However at this stage, we do not see the need to relax the reverberation (RT) times in refurbished buildings, since the Essex Study has shown clear evidence of the benefits of reducing RT. Sports Halls are challenging spaces to design and therefore a clear and detailed calculation process must be provided, to ensure the on-site performance of these spaces.

 Finally, with regards to noise ingress, we see that the proposed maximum 55 dBA noise ingress level for the 200 hottest hours of the year, could be considered as too lenient, and could result in complaints as a result of communication challenges. We also feel the statement relating to the acoustic performance of single sided vented facades and façades to cross vented spaces at 16 and 20 dB could be a little too simplistic.

BB93 Updates – Lean, Green and much much Clearer

BB93

MACH Acoustics aims to lead in the acoustics design of low carbon buildings and open plan teaching spaces, and hence has considerable experience in the design of educational buildings, please see our book ‘Sustainable Acoustics’ found at http://www.machacoustics.com/sustainableacoustics/acoustics-vented-facades.

To achieve the above goal, MACH Acoustics works closely with the Architectural Department at the University of Bath and the Institute of Sound and Vibration, University of Southampton. Currently we are sponsoring a KTP, PhD and two MSc Projects, all linked to the design of low carbon building design.

In MACH Acoustics view, BB93 has been intelligently updated with increased clarity and flexibility towards low carbon and refurbished buildings, whilst providing a more inclusive design approach to pupils within our schools.

Clarity

Clear objective performance requirements are provided in BB93 2014, with many areas being clarified.

For example, the requirements for SEN are significantly clearer, noise levels under natural ventilation and the use of Alternative Performance Standards, have been enhanced and strengthened, with new minimum performance standards being provided.

The challenges in refurbishing buildings have been recognized, with internal noise levels for refurbished projects being relaxed by 5 dB, and sound insulation levels reduced by 5 to 10 dB between spaces, depending upon adjacencies.

An increase of 0.2 seconds in reverberation time has also been provided for non-sensitive teaching spaces. These practical changes will make things considerably easier and encourage the refurbishment of buildings.

Low carbon building design is fundamental to our future buildings, BB93 2014 therefore allows internal noise levels to be increased by 5 dB if natural ventilation is being used, irrespective of ventilation rates. MACH Acoustics research indicates that this could result in 50% more schools being naturally ventilated. To promote cross ventilation, the target across cross ventilators has also been cut back to 32 dB Dnew. This dramatic change will significantly increase the feasibility of using cross ventilation, improving ventilation to teachings spaces and allowing for natural ventilation on noisier sites.

Sound Insulation

Sound insulation has in the main remained unchanged for new builds. The maximum level of sound between exceptionally sensitive spaces has been reduced from 60 to 55 dB DnTw, where this is seen to be a more practical performance standard. Additionally, essential doors between teaching spaces are now allowed, providing a 35 dB door is used.

Reverberation Times

As per sound insulation, reverberation times in the main remain unchanged, with the exception of Sports Halls. The target reverberation time is now a function of its size. Open plan spaces typically gain bad press for their poor acoustics. The tightening and additional new performance requirements relating to speech privacy between work spaces and the reduction in reverberation time, is pleasing to see. These important more stringent changes will result in enhancing the separation between workspaces, reduce occupancy noise levels and enhance communication between teachers and pupils.

Areas of concern

In MACH Acoustics view, BB93 2014 is a significant improvement over the old BB93, providing clearer and possibly more appropriate performance standards. However at this stage, we do not see the need to relax the reverberation times in refurbished buildings, since the Essex Study has shown a clear detriment of increasing reverberation times.

Sports Halls are challenging spaces to design and therefore a clear and detailed calculation process must be provided, such to ensure the on site performance of these spaces.


Finally, with regards to noise ingress, we see that the proposed maximum 55 dBA noise ingress level for the 200 hottest hours of the year, is too lenient, and could result in complaints as a result of communication challenges. The statement relating to the acoustics performance of single sided vented facades and façades to cross vented spaces at 16 and 20 dB, is seen by MACH Acoustics to be simplistic, optimistic and lacking in evidence.

Easy Sound Test – MACH Testing

Acoustic Testing
Easy Sound Test - MACH Testing

Easy Sound Test is an innovative new service from MACH Testing. If one of our engineers is in your area, you get a cheaper sound test. It’s as simple as that. Choose from our calendar of available dates to take advantage of our best prices. Our engineers are on call across the country and offer a fast and professional service. We are an ANC accredited acoustic consultancy, and have been in the business for over 10 years. This means that we not only offer our customers the cheapest sound tests, but also the highest level of service and advice.

MACH Testing also offer Air Testing, for full pre-completion testing.

Lecture Theatre Design with Acoustic Modelling

BB93, Lecture theatre, Resources, Reverberation time
Lecture Theatre Design with Acoustic Modelling

MACH Acoustics were appointed to carry out acoustic design for the refurbished Clattern Lecture Theatre. MACH created an acoustic model of the lecture space, calibrated by acoustic testing of the existing site. The design report concentrated on the two main factors effecting lecture theatre acoustics:

Speech Ineligibility

A standard requirement for a lecture theatre is to achieve good speech intelligibility of the speaker throughout the whole audience within the space. Speech intelligibility is maximised by increasing the signal to noise ratio, that is by maximising the loudness of speech and minimising the ambient noise level. Thus, the acoustical design of rooms for speech reduces to the consideration of four factors:

  • Providing optimum reverberation time.
  • Eliminating acoustic defects such as echoes and flutter echoes. 
  • Maximising the loudness in the audience. 
  • Minimising the background noise level in the room.

Speech intelligibility can be measured by the ‘Speech Transmission Index’, a percentage between 0% and 100%. BB93 requires that areas designed for speech should achieve ‘good’ speech intelligibility, corresponding to an STI of at least 60% across all areas of the audience.

Reverberation Time

Reverberation time is not only important for speech, but also important for audio visual presentations, as well as for amplified speech. For example if a film or a music track is being played from the AV system it is desirable to have a low reverberation time to ensure that amplified sound is clean and intelligible by reducing the build up of reverberant noise that can muddy the sound. This is seen clearly in spaces such as cinemas, which are heavily treated with absorptive material.


Onsite Tests

In order to accurately construct the model, MACH Acoustics carried out tests to determine the current levels of speech intelligibility across all areas of seating. Sound pressure levels were measured at various points around the room with a loud speaker playing in the position of a lecturer. The results are shown below. To put this into context, a 10 dB difference is usually perceived by the human hearing as a doubling in loudness.
Lecture Theatre Design with Acoustic Modelling

The results show that levels in the wider areas, even when at a comparable distance to a position in the centre of the room are significantly lower. Levels at the back of the room are very similar to those as wide seating positions in the first few rows. This occurs mainly for two reasons.

  • The seating arrangement spreads wide from where the lecturer would typically be stood. Hence the lecturer must constantly turn to address different sections of the audience in order to be heard. Consequently when he or she is facing towards one side of the room, the level heard on the other side of the room is lower. MACH would usually advise that a seating arrangement is a) in front of the speaker and b) has an angle from the speaker to the widest seating position that does not exceed 30○ (currently as much as 70-80○). 
  • The front portion of the ceiling is angled and reflective. MACH would usually advise this type of arrangement, as it aids in reinforcing sound levels towards the rear of the theatre by angling early sound reflections towards the back (as illustrated below). Hence as in this case, the sound is more evenly distributed across the majority of the audience behind the first few rows. This can be achieved by a sloped ceiling as in this case, or by suspending angled reflective panels (available in a range of aesthetically pleasing designs) above the area where the lecturer would usually stand.

Acoustic Model

An acoustic model was created, based upon the test data. The model allows us to assess the space by estimating the reverberation time and the spread of sound across the space, as well as the ‘Speech Transmission Index’ (STI) for speech intelligibility.


Lecture Theatre Design with Acoustic Modelling

Ideally MACH Acoustics will usually target an STI of at least 65%, ‘ideal’ speech intelligibility and it can be seen that this was the case in all areas of the theatre. The reverberation time in the existing space is on the high side for amplified AV presentations. It was therefore deemed desirable to reduce this in the design of the refurbished theatre.

New Design Options

Using the model, MACH Acoustics developed a number of design options for Kingston University, providing varying levels of acoustic treatment to reduce the reverberation time and allow for better travel of speech within the space.

Lecture Theatre Design with Acoustic Modelling

All options offered reduced reverberation time from 0.7s to 0.5s and under, with increased STI at back and room edges.Whilst MACH Acoustics had a recommended best options, the various methods allowed the client to select the best design style for the build.


Case Study: Llwynderw Primary School

BB93, Case Study, Cross Ventilation, Exhaust Stacks, NAT Vent Attenuator, Natural Ventilation, Sustainable Acoustics, Vented Facades

Llwynderw Primary School is a project in Abergaveny that MACH Acoustics worked on in partnership with Stride Treglown Architects and Willmott Dixon. The school incorporates natural ventilation through a vented facade and openable windows, which cross ventilate classrooms via a central chimney – saving money, building space and simplifying the construction.

Case Study: Llwynderw Primary School

An important stage in the acoustic design of a building is an environmental noise survey of the existing site, a service provided by MACH Acoustics. Using the data collected, a dynamic noise map was constructed and used to access the noise levels at each facade and the resulting noise break-in within the teaching spaces. It was clear that the site was not particularly noisy and that an open window would provide enough attenuation at the facade facing away from the roads – simple and low cost.

Case Study: Llwynderw Primary School

A ventilation strategy was developed in close coordination with Stride Treglown Architects – using the sound map – which efficiently attenuated noise on each facade. On the noisy road facing facades, a cedar shingles feature created a duct, with intake perpendicular to the ground and containing the NVA. A 90deg arrangement like this increases attenuation and minimises impact on building space – highlighting the bespoke design options that the NVA offers. The quieter rooms with central chimney simply used openable acoustic windows. The central chimney shown above is the highlight of the natural ventilation project. Each stack of classrooms featured a small square chimney, which vented out through natural vent towers on the roof of the building.

Case Study: Llwynderw Primary School

A testament to the NVAs versatility whilst maintaining class leading acoustic performance, the build was impressive architecturally whilst naturally ventilating and meeting both BB93 and BB101 requirements as a teaching space. Thanks to a partnership between MACH Acoustics and Strides, the building received a BREEAM ‘Very Good’ rating and was well received by parents, pupils and residents of the area. Click the preview below to download the full case study:

Case Study: Llwynderw Primary School
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