Max Reynolds says “As part of the Colston Hall bid, MACH Acoustics produced some flythrough animations of the existing and proposed halls. The animations not only included a visualisation but also an auralisation of the spaces to allow the viewer to get a feel for the relative lighting and acoustic characteristics of the two spaces.
The Colston Hall in Bristol is to be redeveloped – providing the funding is in place the transformation will start in 2017 – the hall’s 150th year – and could take two years. The redevelopment will include remodelling the auditorium, its balcony, roof and an overhaul of the smaller Lantern venue. It will also restore the iconic Victorian frontage and open up the building’s cellars for the first time in 100 years where educational workshops take place. The call for bids to enter this competition came earlier this year, and MACH Acoustics was pleased to spend some time in this great venue gathering ideas to propose for acoustic consultancy.
Existing Hall as above image
New Hall as proposed
Generating animations like this requires:
· Building an acoustic model of the space and defining an animation path through the model
· Generating impulse responses at set intervals along the animation path
· Convolving these impulse responses together with audio to generate the auralisation through the model
· Enhancing the acoustic model visually and carrying out a similar process to generate the visuals along the animation path
· The audio and video then need to be joined together and the final animation is created
The real power of an auralisation is that it allows us to hear what the space will sound like before it is built. The visualisation is an essential component in giving the viewer some context of what they are listening to. This sort of animation can be used to highlight different configurations and how this impacts the visual and acoustic characteristics of any given space. Producing auralisations like this provides an unrivalled level of clarity and understanding between the acoustician and the client and the rest of the design team of what a space will be like, maximising the chances of end user satisfaction.”
So, as to the result of the competition – did we win? No, but Ze Nunes and the MACH Acoustics team were invited for interview which gave them a good opportunity to meet the architect Levitt Bernstein and the Colston Hall panel. The architect made some complimentary observations, and in terms of being Bristolians the MACH team will be winners yet enjoying the Colston Hall one day in full glory.
The MACH Acoustics construction detail finder is an innovative new free online tool that allows the design team to instantly obtain suitable lightweight construction details. The simple to use navigation system allows the user to first select the approximate level of sound reduction they require, and then the type of detail needed (head/roof, plan and foot/screed). The user then indicates a frame, soffit and/or ceiling type (when applicable) to find a specific detail. The image can be downloaded, and the process repeated, quickly building up a selection of details in a matter of minutes.
The construction details of floors, walls and junctions in a building are critical to its acoustic performance. It is important to consider that sound not only transmits direct through a wall, but also through flanking paths around the partition through adjacent walls, floors, ceilings, junctions and penetrations. Inattention to these details can seriously degrade the level of sound insulation from room to room, leading to unexpected poor performance in pre-completion testing, occupant complaints and the requiring of remedial work. On the other correct detailing can ensure a level of performance equivalent or better than design targets, giving an excellent acoustic environment. In some cases this will even lead to cost savings by value engineering of wall and floor types, in the knowledge that the risk of flanking sound transmission has been minimised.
This tool is in development and we are open to all comments and suggestions to help improve the way that we work with our clients.
University of Bath: The Arts Building, The Edge
Location: Bath, Somerset
Contract Value: £6M
Images supplied curtesy of Madeleine McEwan for FCBStudios
Images supplied curtesy of Madeleine McEwan for FCBStudios
Designed by FCBS Architects, this project included an acoustic uplift in the theatre; with the addition of a new building incorporating recital and rehearsal space; complimented with a full suite of recording and control rooms; drum rooms; and practice areas.
Sound insulation levels were as high as 65 dB in some instances and background noise levels have largely been designed to NR12.
MACH Acoustics was brought in to consider the acoustic quality of the different spaces and 3D acoustic modelling was used as part of our investigations.We were mindful of value engineering from the outset, working closely with the architect throughout the project. To ensure the acoustic specification was met, MACH proposed more cost effective constructions to the design. We also reviewed areas where the acoustic specification did not meet client expectations and came up with solutions to the reverberation problem in the large drama hall and music rooms, continually testing throughout the process.
Now open and enjoying full usage, this building is an asset to the communities of Bath University and non students alike.
Freshly written, this new CPD was the inspiration of Josh Childs, an expert in the field of education acoustics consultancy. When asked what prompted him to write such a presentation Josh explained that the same issues and problems kept arising and his experience of working on so many schools led him to believe his solutions could also benefit others if explained in advance so shortcomings could be avoided. Josh believes there really are only one or two viable solutions which are cost effective, and this CPD highlights the best practise.
Josh explains “Acoustic design should be considered from junction details all the way to building orientation and layout, so we want to demonstrate the fundamental acoustic principles that you will need to consider throughout the building design.
This CPD will cover the new requirements from the updated BB93 and look at topics such as;
· Getting the most out of your music spaces;
· How to naturally ventilate in noisy areas;
· Gyms and sports halls – common problems and the solutions;
· How to work acoustics within sustainable design (thermal mass, CLT, alternative materials etc);
· Atriums, ‘Streets’ and breakout spaces – creating the right environment;
· Introducing our free online acoustic design tools.”
This CPD gives architects more to think about when approaching designing a school and getting the layout right. For contractors they will benefit from value engineering nuggets. MACH provides a comprehensive review of common acoustic problems that occur within educational buildings and the best methods to solve them.
Rw and DnTw – Knowing the Difference can Save You Money
A common confusion in specifying wall types for a building lies in the difference between Rw and DnTw. Misunderstanding this can go either way in terms of under or over performance; therefore getting this simple difference goes a long way to ensuring a good result on site, as well as presenting value engineering opportunities.
DnTwis a term that relates to on-sitesound insulation. This is the target that is measured against in pre completion testing in line with BB93 specified DnTwvalues. Because it is on site, it accounts for all sound transmission paths including direct through the separating partition and any flanking paths around it (i.e. through ceiling voids, ventilation paths, junction detailing).
Rwis defined as a laboratory rated sound reduction index. Wall constructions should be specified as this, measured in isolation from any other sound flanking paths.
Why is this Important?
The same construction measured in a lab will get the same result every time, but measured on site will vary from room to room, project to project. The conversion from Rw to DnTw has to account for the size of the separating partition, the volume and reverberation time of the ‘receiving’rooms. It must also incorporate a factor to account for potential flanking transmission on site due to construction quality or inattention to junction detailing.
Therefore it is not a simple case of RW = DnTw + X dB. The RW can vary significantly between partitions, even if they require the same DnTw. Figure 1 summarises this.
How does this Help?
Clearly from Figure 1, if the same wall type Rw (say 45 dB) is used everywhere the DnTw is 40 dB, there will be rooms that fail. On the flip side, if the most onerous requirement of 53 dB RW is used for all 40 dB DnTw walls, then some areas will be exceed the required performance by a considerable margin.
Of the two scenarios, it is usually the latter that will occur within a design. Therefore clear cost savings could be made by assigning wall types to partitions based on the required RW, not simply the DnTw.
This can all be done whilst retaining the same number of wall types. In fact by careful design and attention to construction details, the build ups of wall types can be engineered to reduce unnecessary overspend on thicker or denser plasterboard products and still maintain the on-site acoustic performance.
Reducing every dB of overdesign quickly sums up when applying over projects, schemes and larger frameworks, particularly those with common shared constructions.
MACH Acoustics was delighted to be appointed for the design of a beautiful new chapel redevelopment in Stroud. Architect Nic Pople is much respected amongst the congregation of Stroud as he recently also worked on their newly rebuilt church of the Christian Community in Temple Lodge, London. The new chapel in Stroud was constructed from CLT and was to be positioned right next to Cainscross Road, a busy main road that passes through the centre of the town. Therefore the façade construction and windows had to be very carefully specified to ensure that indoor ambient noise levels would not be compromised.
In order to understand this project and sources of noise fully MACH Acoustics used noise mapping as shown in the following image
The façade design was developed in conjunction with a natural ventilation strategy. Despite the high external noise levels, this was achieved by drawing fresh air in from the quieter South façade at low level in the chapel basement and was exhausted at high level out of an attenuated stack into the atrium. This needed to be done with care such to not allow plant noise to compromise the low indoor ambient noise level requirements of the chapel.
The chapel itself featured some interesting geometry – challenging yet exciting to work with
Large periods of the services are held with the speaker facing the altar away from the congregation, therefore MACH Acoustics used extensive 3D modelling to maximise the speech intelligibility within the space. In the absence of any definitive design targets for the church, MACH Acoustics generated a series of auralisations to highlight to the client how the new chapel would sound. The thriving congregation can enjoy their new space and will no doubt appreciate how sustainable the building truly is.
This drawing above shows the sound source (speaker) facing the alter
The above drawing shows the speaker or sound source facing the congregation
Painting a Picture of Sound Insulation
MACH Acoustics have experience of working with a number of constructions, from standard off the shelf lightweight metal stud walls to unusual timber cassette panels to bespoke ideas as part of a decorative effect. Whether it be a new build residential block or a Grade II refurbished building fitted for offices or teaching, MACH always take a detailed design approach to ensure a high level of acoustic performance, whilst achieving a cost effective and carbon neutral design.
The Task at Hand
MACH Acoustics were asked to investigate the level of sound insulation that would be achieved from the introduction of new glazed breakout ‘pods’ and the adjacent atrium at Lacon House in London. The interest laid in the feature design ‘picture frame’, a timber lining around the external glazed walls of each pod. Despite the open feel of these pods, the task was to ensure that noise within the atrium would not be a disturbance in the acoustically sensitive pods used as meeting rooms.
MACH applies a structured approach to these kinds of problems, realising that sound transfer not only comes through the wall or glazing, but also from flanking through junctions with adjacent elements, in this case the feature design picture frame. Simply upgrading the construction of the glazing does not work when the flanking performance is poor, hence by looking at the bigger picture MACH are able to avoid over expensive designs that don’t work and focus on cheaper, high performing solutions through clever considered engineering.
In this case, MACH componentised each possible transmission path to consider the sound reduction through each, zeroing in on the areas that had the most influence on the overall sound insulation. We used our extensive collection of manufacturer test data, on site test data and modelled performances to accurately calculate this.
This approach allowed MACH to tweak details around the frame and glazing until a high level of performance was achieved, keeping the thickness and expense of the glazing to a minimum and achieving an aesthetically pleasing design.
When the Romans invented the glass window, they couldn’t have anticipated the environmental context and settings years later: Windows continue to let in light ages on, however undesirable levels of air and sound also intrude.
MACH Acoustics recognises the importance of noise control through window design. Where simple traditional design limits the use of open windows, we have now developed a range of unique software tools to help overcome noise break-in in residential buildings, offices and schools to prove that open windows can be used in noisier environments than previously thought.
Working with your design, we will improve the acoustic performance of open windows and provide the solution that will work best for your project. It could be as simple as an extended window frame, proven to reduce sound; external baffles; or changing the shape of the window itself.
Download our book for free from iTunes to read how our ground-breaking, software tools can show you the future of windows, and check out the video clip also below.
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 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.