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Noise free open windows…A tall story?

Acoustic Design, FDTD modelling, Window Design
A new build range of large residential projects within an Asian capital city (confidential) for the public sector fitted well with our commercial research and development. MACH’s uniqueness in this field facilitated the creation of a new in house software package, implementing Finite-Difference Time Domain (FDTD) mathematics. This software package allows us to model bespoke constructions on a project by project basis, such that solutions are new and innovative.
Sound Insulation of Open Windows and Balconies
Introduction
The use of purge ventilation to naturally ventilate a building, can provide a significant challenge in regards to external noise ingress through the façade and open windows.  Typifying the burgeoning requirement for affordable and luxury city centre accommodation, our client wanted bespoke options for a number of confidential, high-rise residential,overseasprojects.
The challenge is providing noise control measures without the use of bulky attenuators, thermal dampers and ugly weather louvers.  We pooled our experience in building acousticswith Dr Steve Lo, Senior Lecturer in Sustainable Environmental Engineering at the University of Bath, to investigate the potential of noise mitigation by balcony shaping and other façade design options, in order to screen open windows from external noise sources such as road traffic.
Acoustic Modelling of Noise Ingress and Mitigation
The FDTD software was mainly developed in-house, but also through two MSc projects being supervised by Dr GwenaelGabard and Dr FillipoFazi at the ISVR, funded by MACH Acoustics.
FDTD is similar to commercial Finite Element (FE) modelling but has the advantage that the sound pressure field can be animated over time, allowing the wave propagation to be visualized, measured and assessed.  A visual representation is a strong advantage in understanding the reflection and diffraction around walls, windows, balconies and screens.
‘Quiet’ Balconies
Balconies exhibit interesting differences in sound propagation depending on the height and distance from the road.The linked model video belowshows the nature of sound reflections off the balcony façade and soffits, used to assess one of the towers within this development.  Adjusting the shape and finishes of these surfaces has shown value in reducing noise ingress into the proposed residential accommodation. 
Noise free open windows...A tall story?


From the above model, a more detailed view can be presented to show just a single flat/balcony.  The images below show a standard single balcony, with a reflector then built from the soffit in the direction of the source (road traffic) to direct sound back away from the balcony.

Noise free open windows...A tall story?
Figure 2: FDTD model of a single balcony with (bottom) and without (top) a noise mitigating reflective panel

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Back to school study pays off for the Steiner Acadamy

Acoustic Design
Collaborating with Feilden Clegg Bradley Studios and Kier, the Steiner Academy Frome (encompassing D&T workshops and music classrooms teaching spaces) is a new build and refurbishment project which provides an outstanding example of maintaining a unique and specific style whilst overcoming acoustic challenges inherent with CLT coupled with a tight budget.

Back to school study pays off for the Steiner Acadamy

How was it done?  We used both on-site CLT test data and extensive modelling (using proprietary software and internal principle calculation) to review and assess the sound insulation design from all angles. Additionally the layout was also reviewed with the structural engineer to determine the extent of the CLT span and thus determine the re-radiation from the exposed surfaces. From this, we achieved a highly accurate understanding which enabled detailed advice in regards to the placement of strategic breaks in CLT slab, linings to the slabs as well as specifying minimum slab thicknesses.  In addition, the method of structural connection was reviewed to minimize flanking.



Back to school study pays off for the Steiner Acadamy

Due diligence and impressive investigation was given to the design of the refurbished spaces, carrying out extensive early testing of the existing Victorian hospital buildings frame. From these tests, cost effective wall and ceiling linings were specified so to achieve BB93 performance criteria. Not only was cost consideration a driving factor, minimising material usage was a client and
architect focus.


Back to school study pays off for the Steiner Acadamy

It was this focus that formed the drive for CLT, i.e. a zero carbon form of construction. Thus the time spent studying and researching the mathematics behind statistical energy modelling and modelling of sound insulation of multi layer elements, combined with calibration to existing on site data, has pushed MACH Acoustics and potentially our industries understanding for elements making up sound insulation.
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Bath University PhD helps us see what we hear

Acoustic Design, Natural Ventilation
MACH’s very own Ze Nunes is embarking upon a PhD at Bath University, and the research he will do should not only change the way acoustics is heard but also viewed. 

Entitled, “A common Multi-disciplinary visualization of sound and air in low carbon building realizes modern building design intent fully”.
He justifies that the lack of design solution and basic conceptual understanding of acoustics is often the reason for not taking a low carbon building design strategy forwards – the primary aim of this work seeks to ensure that all stakeholders in the design process are equipped with the necessary knowledge to engage them fully in the design, enabling them to delivering better buildings as a result of reduced conflicts. A shift in the appreciation of acoustics in low carbon buildings is required – this will make acoustics an incorporated aspect of the design process, and not merely a stand-alone remedial discipline.
The invisible link between acoustic and natural ventilation paths in buildings results in conflicts between other disciplines, limiting the full environmental potential of a building to be realized.This lack of understanding can be breached by using inspirational collaborative methods to inspire key stakeholder engagement. Modeling techniques, interpretation of data, seeking symmetry of physics in the properties of a building will all assist in presenting the building in a more visual way. The principle behind this concept being, “if you can see the acoustics we can fully understand the acoustics”.

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Frozen – the best Ice Arena in Cardiff’s Kingdom

Acoustic Design
Ice Arena Wales – Case Study

The brief: provide a unique sports facility comprising two ice rinks (3000 spectator capacity) and a range of supporting ancillary spaces to Cardiff and Wales which can also provide a flexible arena for a wide range of events.

Frozen - the best Ice Arena in Cardiff's Kingdom
Frozen - the best Ice Arena in Cardiff's Kingdom 

Acoustic challenges such as planned hotels and residential accommodation surrounding the Ice Arena, mean that noise break-out from the arena is a major concern. The ability to play high sound levels within the spaces is directly linked to the building revenue stream.

These factors are now accommodated into the design essence of the building. Specializing in “Acoustics for facades”, MACH was able to model the acoustic performance of the proposals and provide alternatives could reduce costs and reduce risk to the project, whilst maximizing the overall stability of the development.

Frozen - the best Ice Arena in Cardiff's KingdomThe core performance of the building structure and shape was established through extensive modeling.  Our models incorporated the PA, allowing MACH to assess the intelligibility and sound quality of the two arenas, under a range of different configurations.  

The modeling process was subsequently used to tune and adapt finishes within the Arenas, maximizing their potential flexibility, resulting in a dynamic building making the most of its potential revenue. The architectural appearance, thermal performance and acoustic insulation provided by the façade, are all integrated together within this project.  

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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

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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.

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