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.
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