In Part 2 of Architecturally Sound, we continue our exploration of acoustic phenomena in architecture with a look at flutter echo in Mayan Ball Courts. Learn how flutter echo can impact the room acoustics of a space and ways to prevent it.
Want to hear what flutter echo sounds like? Watch my video for a demonstration.
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Case Study: The Great Ball Court
Mayan Ball Courts exist throughout Mesoamerica. The ancient sites are where dramatic ball games of life and death were played. Political disputes and arguments could be settled, with the loser being sacrificed to the gods.
The largest and most acoustically spectacular is the Great Ball Court in Chichen Itza, Mexico. It is defined by two massive hard surfaced stone parallel walls and showcases some wonderful acoustic phenomena. As a result of the design, a profound ‘flutter echo’ can be heard within the playing field.
This phenomena creates an eerie ambience within the playing arena. Echoes of voices, body impacts and the smash of the 9kg rubber ball would have shuddered throughout the arena!
What is Flutter Echo?
A flutter echo is a series of distinct echoes. They are heard with sufficient loudness compared to the original sound. The 'flutters' are equally spaced in time usually 30-50ms apart. This differs from a long delayed echo or reverberation – flutter echoes are multiple echoes that occur in rapid succession.
Hard and smooth parallel surfaces are to blame – they allow for the sound to bounce back and forth in a series of reflections that appear to mimic the source. It is acoustically comparable to ‘infinity mirrors’.
In the case of the Great Ball Court, flutter echoes occur four times every second as the sound decays!
In everyday architecture, untreated hard-surfaced parallel walls should be avoided. It can be very distracting and will lead to poor acoustic comfort. It could also anger the gods!
Seriously though, the end user will complain. Flutter echoes degrade speech quality and are often found in rooms with untreated plasterboard walls and glazing. So this can be very common in meeting and conference rooms.
This phenomena will also prove a problem for audio systems. Rod McKinnon from JANDS has 25+ years’ experience in the application of installed sound systems in both performance and corporate boardroom audio.
“There is only so much I can do, when the acoustics of a room is poor,” says Rod. “The synergy of a fantastic looking space and the practical use of the space is ideal. These details must be worked through early in the design of any functional space for it to be a success.”
There are many ways to prevent flutter echo. It would be easiest to have an acoustic consultant provide recommendations for aesthetic acoustic panels during design stages. This will ensure that the end user is delivered a comfortable environment and that the original design aesthetic is maintained. However, if it is too late - the solution is to retrofit an absorptive or diffusive object in the flutter path.
Acoustic slotted panels on the wall and ceiling in a meeting room at Challenger HQ, Sydney
Slatted panels on walls and ceiling in a consultation room at Gaden Lawyers, Brisbane QLD
In critical applications like music rooms, the geometry of the space can be designed to not include parallel walls. Angled panels and convex surfaces can also be used to break up the effect of a flutter echo.
Other solutions include the use of ornaments and furniture. An example being a bookshelf that can be positioned along one of the problem walls. The geometric irregularity of a bookshelf makes it a suitable scattering device. This can often be enough to begin improving acoustic comfort.
There are numerous geometric combinations capable of producing flutter echo, and flutter echoes can occur in both the horizontal and vertical dimensions.
It is more difficult to treat in the instance of glass walls, especially when the glazing itself is a design feature. There are however solutions that can deal with any potential issues. 'Winging it' doesn't work.
Remember to speak with your acoustic consultant when designing any room for communication.
In Part 3 of the series, we’ll look at a case study about Mayan Pyramids, colouration and different acoustic materials.
Did you miss Part 1 - Why Acoustics Matter In Great Architecture? Go here to read it now>>>
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