Internal noise levels can have a profound impact on the occupants of a building, affecting concentration, productivity, comfort, contentment, well-being and even health.
When designing an interior space, whether for an office, an auditorium or a home, architects and designers have many different internal walling and wallcovering options to choose from, all which play a part in creating an acoustically sound environment.
For acoustic consulting engineer, Ivan Lin, the most important thing to keep in mind when creating and designing a space is that it should be comfortable for the people inside. “Building professionals are ultimately space enablers and our function should be to design spaces that work for the end-user,” he stresses.
User experience design
“Too often client briefs focus on the type and size of building that is required, but does not specify what people would expect from the interior space. Then only, once the building is completed and people move in, we find out whether or not they are comfortable. Instead, we should interrogate what people would be doing inside the building, how they will need to function and how they need to feel in the space, before we start the design,” explains Lin.
“Even in multifunctional spaces, where one is faced by multipurpose application, one should try to identify the core requirement of the space, whether it is music making or music reproduction, public addressing or privacy, and use that core requirement as a design target rather than being mediocre in every aspect,” he advises.
Generally though, in commercial buildings, the main goal is to create private offices, meeting rooms or other types of enclosures within an open space. Lin points out that it is here where a misunderstanding between sound insulation and sound absorption most commonly happens.
“Privacy depends more on how an enclosure is designed than on the type of wall, or what is put in or on the walls,” he states. “It is important to understand how products and materials should be specified and applied in order to realise the optimal performance. For example, it is futile to install a high-spec drywall with glass wool insulation, but then only build it from the floor to the ceiling. It should be no surprise that sound can very easily travel over the wall through the ceiling, but this remains to be one of the most common mistakes made in the industry.”
Another acoustic constraint is mechanical ducting. “One needs to plan the ducting at an early stage because if it goes through the critical spaces, sound can travel through the air diffuser, through the ducting and out on the other side, and you are not going to get the sound insulation they need,” Lin explains.
When it comes to actual material selection, Lin points out that the application of a product is more important than the product itself. “We are often asked which products we use, but to me there isn’t such a thing as a specialist acoustic material. A product that is appropriate for one project might not be right for another, even though the requirements might be similar.
“There are fantastic acoustic materials in the market backed by credible measurements, but there are also many products that don’t have proper test results to back up their claims,” he warns.
“Choosing materials and products is very much design- and application-driven. Being an acoustic engineer, you learn that there is never a budget for acoustics, so we are very well trained to find the most cost-effective method to achieve our goal. We typically try to use common, off-the-shelf building materials such as drywall, brickwork, suspended acoustic ceiling, glass wool, polyester fibre, glass and even metal for acoustic purposes. This is possible by understanding these materials’ intrinsic properties and applying it in the correct way,” Lin explains.
Directing acoustic design
To provide acousticians, architects and interior designers with a baseline reference, acoustic standards exist in the form of SANS 10103:2008 – the measurement and rating of environmental noise with respect to annoyance and to speech communication, which lists ambient noise levels suitable for different occupational spaces.
“However, perception of sound is subjective and we still don’t fully understand exactly how sound works,” Lin points out. “Using science and tabulation can get you far, but experience also counts a huge portion in the overall equation. And although there are fantastic acoustic modelling software out there, these are still very limited and cannot fully express the human experience of sound. We can therefore use computer modelling as a guide, but it should not be a design determining factor.”
Green building credits
In addition to SANS, Linspace has assisted the Green Building Council of South Africa (GBCSA) with the drafting of acoustic credits for the Green Star Office Tool v1 as well as the pilot versions of the interior and performance tools.
“Common to all the acoustic rating credits, noise is addressed as the main criterion, but for the interior tool, three additional points – privacy, interference and reverberation – were introduced since these aspects are very relevant to building occupants apart from noise,” says Lin. “These additions make the interior tool much more advanced than the original, which was based on the Australian credit.”
Unfortunately, mostly due to budget restraints, the acoustic credits are often overlooked while teams focus on obtaining points in the energy and water categories. Even if the importance of proper acoustics is valued, when it comes to the rating process, the process becomes very mechanical with clients looking for the maximum points for their money.
What is the point?
“At the end of the day, the most important thing is to consider the people who will end up using the building. Within the green building movement, we are trying to design sustainably, but to me it just doesn’t make sense to make a building so efficient, when the occupants are not comfortable in there. When it comes to functional issues, the basic criteria should be that the space must work, because if the building doesn’t work for the people in there, it is not sustainable anyway, regardless of how much energy or water is saved,” Lin concludes.
Full thanks and acknowledgement are given to Ivan Lin and Linspace for the information given to write this article.
Johannesburg Council Chamber
Completed in March this year, the circular glass building that is the Johannesburg Council Chamber proved to be quite a challenge in terms of acoustics.
Situated in Braamfontein, surrounded by busy streets, the first requirement was to insulate noise from the outside to the inside. Secondly, with the entire enclosure made out of glass, sound is reflected in all directions creating terrible echoes, something that would be very disturbing during a huge council meeting.
To address these challenges, it was decided to create a second building skin inside, which very effectively reduces noise from the outside to enter the building and at the same time forms a functional walkway around the chamber. The internal skin was further skilfully shaped and angled right around the building to direct interior sound energy towards the ceiling.
“Instead of only depending on absorption to control discrete reflections, we used geometry as the fundamental criteria to manipulate the sound energy and reshape it so that it can be absorbed much higher up in the ceiling,” Lin explains. “In essence we changed the geometry of the space inside.”
The acoustic treatment for the Soweto Theatre had to accommodate speech in theatre productions, so the acoustic properties are very different to a venue that is intended purely for music production.
“Although there is uniformity with regards to the red fabric covering throughout the theatre, some of the wedges are sound absorptive while others are sound diffusive,” Lin points out. “It is a good example of how it is possible to provide a homogenous aesthetic expression with different kinds of acoustic treatment behind it.”
St Mary’s auditorium
Designed mainly for music production, St Mary’s timber-clad auditorium features purely sound-reflective surfaces that diffuse the sound.
Caption Main Image:Although there is uniformity with regards to the red fabric covering throughout the Soweto Theatre, some of the wedges are sound absorptive while others are sound diffusive.
© Tony de Oliveria