Architecture today is not just about engaging the visual sense but is also factoring in sense of touch and sound to make the buildings more holistic and in harmony with occupants well-being. While the science of architectural or building acoustics is well understood, using that science to create desired acoustical performance is complex. Roopa Krishnamurthy, Owner, Soundscape India Acoustical Consultancy gives a deeper insight.
A good acoustical design isn’t a luxury anymore but a necessity that impacts employee productivity in offices, performance quality in auditoriums, functionality in public spaces and occupants comfort in residences. Historically, acoustics focussed only on controlling the reverberation times and loudness of spaces where, the acoustical palette consists of three ingredients absorption, reflection and diffusion. Architectural acoustics manages both airborne and impact sound within a building design.
- Noise transmission from building exterior envelop through walls, windows, roofs, etc.
- Sound transfer from one interior space to another via ceilings, room partitions, ducting and doors & windows
- Sound reflection within a room from walls, floor, ceiling, furniture and other surfaces
Applications of acoustics differ according to the problem each specific space., Commercial spaces such as malls usually have public address systems. Typically one finds that the whole place reverberates with loud sound but the speech is barely intelligible. Here, speech intelligibility is the biggest problem and fixing reverberation to some degree will mitigate this. For residential buildings, noise control is a bigger problem, so we’re talking about airtight partitions and windows here. For Hospitals, noise control is again the main issue especially, if rooftop units lie in vicinity of residential apartments, etc. For educational institutions, we have to look at both speech clarity as well as soundproofing/ background noise. For corporate spaces, background noise is a much bigger issue. In general all large public spaces should have good sound systems in the assembly areas and the acoustical environment should offer good speech intelligibility – as a safety factor in case evacuation messages have to be broadcasted. This applies to malls, cinemas, train stations, airports – practically everywhere where a congregation/crowd gathers. The most important thing to understand is that soundproofing and excess reverberation are usually not solved by the same product. It is unfortunate that the there’s deplorably low awareness of this even with people who sell acoustical products and we see a lot of money wasted in experimentation before someone consults us.
Predicting acoustics using technology
What’s important is that the acoustical solution matches the architectural and functional intent. The latest software and simulation technologies are providing the tools for designers and consultants to achieve optimum results. Already, 3D modelling and Fly-thru animations provide the ability to experience a building’s design before its execution, now aural rendering tells us how it will sound during a specific function.
A 3-D model of the space is transferred to an acoustical modelling software and acoustical materials are assigned to the modelled room’s surfaces (or potential construction materials) and sound sources and listener locations are identified. The software then calculates the propagation of sound from the source to the listener using algorithms based on ray-tracing combined with statistical reverberation calculation and other techniques to account for sound reflection, scattering and diffraction. The calculated room impulse responses are then convolved with audio material that has been recorded anechoically – in a space free from echoes or reflections – to generate results that depict the properties of that room. Some part of these results can also be experienced through auralization. With more materials being tested, we are able to get reasonably accurate predictions of how the building will sound even before it comes up. For sound insulation, the prediction software help get a broad number, but acoustic consultants only rely 20% on what the software says. It is important to understand under what conditions the simulation occurred and what assumptions have been made. In real life, you could be off by a large margin if you don’t take site conditions into account. Getting the site conditions right is the larger part of the simulation, the other part being, understanding material science and resonances. As to the methodology, each soundproofing system inherently works as a mass-spring-damper system, and understanding that is key to predicting the performance of the system.