Keep passing the Open Windows

29th January 2018Natural Ventilation, Window Design

Introduction

This Blog Post is taken from the latest MACH Acoustics book “The Acoustics of Open Windows” – Chapter “The Future of Windows”. This book can be downloaded as an iBook from: https://itunes.apple.com/gb/book/the-acoustics-of-open-windows/id1049860606?mt=13

This book publishes part of Ze Nunes’ ongoing PHD, on the subject of visualizing sound and air in low carbon buildings.

At MACH we see that natural ventilation is one of the strategies of choice for forward thinking clients interested in low-energy buildings. However environmental noise break-in can be an issue, resulting in clumsy acoustic attenuators or windows being kept shut.

MACH Acoustics recognizes the benefits of noise control through window design. The team at MACH has therefore developed unique modeling tools, assessing noise mitigation solutions based around improving the acoustic performance of open windows, such to overcome noise break-in issues to residential buildings, offices and schools.

Extended Window Frame

One of the key factors affecting the sound reduction of an open window, is its ability to screen sound, i.e. the harder it is to see the sound source through the opening of the window, the better its acoustic performance. Hence by simply extending the frame of the window, as shown, the sound reduction of a simple window can be enhanced. The next two slides illustrate this effect, with an interactive model showing the effects of extending the frame and a video providing a subjective illustration of this change.

Baffled Facades – Illustrations

An alternative way of enhancing the performance of an open window it is place a baffle over its opening. MACH Acoustics’ analytical tools and measurements facility can be used to determine the size and position of the baffle such to provide the required acoustic performance from an open window.

Weston-Super-Sound Town Hall

29th January 2018FDTD modelling, Noise Mapping

Weston Town Hall, Weston-Super-Mare (client North Somerset Council), a collaboration with Alec French Architects and Willmott Dixon is now a completed refurbishment project with a contract value of £9.7m.

Going over and above standard guidelines, MACH Acoustics focused on analysing the spread of sound pressure level and the speech intelligibility over distance, rather than purely focusing on reverberation time in the sense of traditional design. MACH used extensive computer modelling and produced video/audio simulations (‘auralisations’) to demonstrate the acoustic benefits in respect of the aesthetic views of the architect, the budget of the project, the low carbondesign initiative and the satisfaction of the client. This allowed us to evaluate the level of acoustic separation between desks and groups in large open plan areas, with and without noise mitigation methods including desktop screens and acoustic soft treatment.

Through past projects it has been often found tricky to determine how much acoustic treatment is needed in a space. MACH have experienced complaints from open plan offices with high quantities of treatment, to very little complaints from occupants in an effective concrete frame with no acoustic treatment.In addition BCO guidance recommends a highly acoustically absorbent soffit, which poses problems with low carbon exposed thermal masses, aesthetics and additional cost. Hence this traditional reverberation time based approach is seen to be limited in open plan developments

Our approach focused on the reduction of sound pressure level (SPL) over distance, and the level of speech intelligibility (STI) between individual and grouped desk areas, presenting results through auralisations and videos to provide a cost effective sustainable solution.

A multitude of CATT Acoustics models were created to assess several factors. Firstly effective was the addition of acoustic treatment in the form of suspended rafts above the walkway between desks and later above desks, Whilst the absorption coefficient of these are similar to BCO traditional guidance, the quantities of panels are vastly reduced by specifically placing them in the most effective areas over desks and cabinets/shelves to reduce noise transfer (Figure 1).

Figure 1: Increasing acoustic separation by placing suspended acoustic rafts over desks

The next step was to introduce screens to enhance the acoustic separation between desks (Figure 2). The most effect. Whilst combining the full extent of suspended rafts and screens provide the best option acoustically, it was considered by the design team that a combination of the screens and the initially proposed amount of suspended treatment was the most cost effective solution. Still, this achieved a reduced transmission of sound in line with what traditional BCO guidance would have provided, with the benefit of reduced costs and a lower carbon footprint.

Figure 2: Increasing acoustic separation by placing screens between desks

Presentation of Results

As an acoustic consultancy we understand that it is our client and end users that benefit or suffer from the result of our work. We therefore prioritize the importance of good communication. The illustrations within this document have been taken straight from our acoustic report and were complimented by a set of auralisation videos that were distributed to the design team and client. Links to these three videos are provided below.

http://www.youtube.com/watch?v=tl0TQPJ1fBc

http://www.youtube.com/watch?v=fLFmBpohHCc

http://www.youtube.com/watch?v=FbVSuItgatI

Easy Sound Testing… How do they do that?

29th January 2018Acoustic Testing

The uniqueness of this project is that we have taken a standard process and studied every element with the chain of delivery. We have then improved every aspect of this chain, but using highly innovative solutions based upon a wide range of engineering solutions.

Within a competitive industry clients need to be getting fast and accurate results delivered in a way that suits and helps them. This project started by looking at our booking process, the organization of test equipment and our data processing methodology. The second goal of this project was to reduce our carbon footprint and to look at opening new markets in the field of sound testing and measurement.

Booking System

Various staff taking calls and booking them into a diary, is that as good as it can get? The solution has been to create a web based data system, containing information relating to test locations, our equipment, cars and engineers available for testing. By cleverly arranging this database, our staff and clients can use our web based booking system, which provides more competitive testing rates on the grounds that we know that we are in a customers area. Since the location of every sound test, meeting and environmental noise assessment is sorted though a single booking system, our efficiency is increased dramatically.

In effect, our system works the opposite way to Easyjet, hence the name Easy Sound Testing. The maths behind this relatively simple idea is complex, however we have shown that we are reducing the cost to clients and have cut our testing mileage by more than 15%. We are now looking to increase this figure to 25%.

Data Processing

Issuing reports on site brings many advantages, including client satisfaction and the ability to investigate and support clients in the case of failures. The time advantage this brings to the tester is also important, improving accuracy and increasing profitability as the report is generated immediately.

To do this, we have developed our own software. The software works by taking on site data relating to room dimensions, test locations and file data numbers on the sound level meter. Upon the completion of the test, the software uploads raw excel test data from a Norsonic, NTI or B&K sound level meter and combines it with the site notes initially entered into the software. The results being a file containing sorted test data combined with on site test information, as well as generating test certificates and tables of results.

By developing an intelligent system MACH has not only reduced its carbon footprint considerably but clients also benefit with a more intuitive system that they can take more control of themselves.

Noise free open windows…A tall story?

29th January 2018Acoustic 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.

Figure 1: FDTD video of road traffic noise propagating into balconies of a high rise residential building

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.

Figure 2: FDTD model of a single balcony with (bottom) and without (top) a noise mitigating reflective panel

ANC Awards ceremony

29th January 2018Awards

And here’s Max receiving the award after his inspiring presentation on the project. A well deserved win in the Educational Buildings category, and a good evening for all at MACH Acoustics.

Back to school study pays off for the Steiner Acadamy

29th January 2018Acoustic 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.

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.

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.

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.

ANC Awards 2015 win with Wallscourt Farm Academy

29th January 2018Awards, Open Plan, Open Plan Spaces, Open Plan Teaching

Pleased to announce that the ANC Award for Architectural Acoustics, Education Buildings was won by the fabulous Wallscourt Farm Academy, Bristol.

Why was this project so special?

Years of research and project experience have enabled us to develop a list of design criteria for the acoustics of open plan spaces. By working closely with the project architect, NVB, we were able to successfully apply these principles to produce a highly functional and usable space. We have also remained in touch with the school, so to further learn how the building functions over the next few years. Wallscourt Farm Academy is seen to be a fine example of how to create an inspirational educational environment through an understanding of the requirements and characteristics of an open plan space. Our work benefited from attending and observing the behavior and workings of various different open plan schools, as well as through data analysis from on-site measurements and CATT Acoustics models.

Open Plan Learning

The question is, is it the teacher or is it the environment that governs pupil engagement? As a result of this question, open plan learning has been on our agenda for many years.

Simplistically, if you remove the walls between teaching spaces, there are no longer any tools to control the acoustic separation between teaching spaces. This is why a quick web search or attending an acoustic conference will have you inundated with the acoustic issues relating to open plan spaces. However the photograph above clearly shows that open plan can be inspirational and highly beneficial.

What If We Remove The Walls?

We see that there must be something better than the square and rectangular classrooms that our children, ourselves, our parents, grandparents and so-on were taught in. Hence we believe in open plan learning and have therefore attempted to change the design of these spaces.

The removal of walls means that we have to focus on STI as a key design parameter, and on communication as our tool to ensure that the open plan spaces are correctly designed. Our logic being that if the acoustic design is not bought into, it will not be implemented, resulting in a space that is not fit for purpose.

The illustration below highlights the main factors effecting STI i.e. ‘enhancing the spoken voice’, left side – yellow, and ‘reducing unwanted noise’ right – blue. The diagram provides a range of design tools with respect to open plan learning/teaching, and is used throughout our design reports. Of vital importance in this consideration are: distance (between pupils and teacher), enhancing the spoken voice, reverberation control (screening and layouts) and also providing quiet spaces.

Bath University PhD helps us see what we hear

29th January 2018Acoustic 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”.

Keynsham Civic Centre triumphs at RIBA South West Awards 2015

29th January 2018Awards

Keynsham Civic Centre was among outstanding buildings honoured in the RIBA South West Awards 2015 from the Royal Institute of British Architects.

Keynsham Civic Centre, Dundon Passivhaus, Hauser & Wirth’s Durslade Farm gallery at Bruton, the Fitzjames Teaching & Learning Centre at Hazlegrove School, Sparkford, the Myrtle Cottage Garden Studio, and the Pod Gallery, both near Bath, all triumphed from an initial entry of 48 projects, and a shortlist of 16 buildings across the region.

Keynsham Civic Centre and One Stop Shop by Bristol’s AHR Architects also won the Sustainability Award sponsored by SIKA. The striking new buildings are approached via an existing street and reveal themselves in the form of the library and one stop shop building, a large gold box floating over a recessed stone and glass entrance area

. MACH Acoustics was pleased to support this project and enjoyed working to its strength of providing sustainable acoustics which really shone through.

Chair of the jury, Andy Ramus, of award-winning

AR Design Studio, said of Keynsham Civic Centre that a great deal of effort had been made by both client and architect to ensure the highest of green credentials.

Frozen – the best Ice Arena in Cardiff’s Kingdom

29th January 2018Acoustic 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.

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.

The 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.

Introduction

Extended Window Frame

Baffled Facades – Illustrations

Open Plan Learning

Posts pagination