March 27, 2007

An ancient theatre filters out low-frequency background noise. The wonderful acoustics for which the ancient Greek theatre of Epidaurus is renowned may come from exploiting complex acoustic physics, new research shows. The theatre, discovered under a layer of earth on the Peloponnese peninsula in 1881 and excavated, has the classic semicircular shape of a Greek amphitheatre, with 34 rows of stone seats (to which the Romans added a further 21). Its acoustics are extraordinary: a performer standing on the open-air stage can be heard in the back rows almost 60 metres away. Architects and archaeologists have long speculated about what makes the sound transmit so well.

In the first century BC the Roman authority on architecture, Vitruvius, implied that his predecessors knew very well how to design a theatre to emphasize the human voice. "By the rules of mathematics and the method of music," he wrote, "they sought to make the voices from the stage rise more clearly and sweetly to the spectators' ears... by the arrangement of theatres in accordance with the science of harmony, the ancients increased the power of the voice." Later writers have speculated that the excellent acoustics of Epidaurus, built in the fourth century BC, might be due to the prevailing direction of the wind (which blows mainly from the stage to the audience), or might be a general effect of Greek theatre owing to the speech rhythms or the use of masks acting as loudspeakers. But none of this explains why a modern performer at Epidaurus, which is still sometimes used for performances, can be heard so well even on a windless day. Nifty!

posted by petebest 17 years ago
  • Great article. I've been to Epidaurus and it really is uncanny. Thanks, pete!
  • But the key can't be all in the low frequencies. Even high frequency sound is subject to the inverse square law. Normal conversation is pretty hard to hear hundreds of feet away in any circumstances. Unless you're in Brooklyn, I guess.
  • Fascinating. Here's some more on the controversial field and theories behind Acoustical archaeology .
  • X marks the spot, boys.
  • There is also a bizarre flutter echo, lasting a few seconds, that can be heard between two parallel walls of the playing field; you can listen to a sound sample here. This acoustical effect is the subject of Lubman's most recent work, which he presented earlier this month at a meeting of the Acoustical Society of America in Hawaii. Invariably, in Western architecture, such flutter echoes arise from design defects, so for decades this effect at the Great Ball Court has been disregarded by archaeologists. Ever the maverick, Lubman believes that in the case of the Great Ball Court, such an echo might have been a deliberate design. Lubmangbc_photo The flutter echo would have been heard every time a ball hit the wall of the playing field -- and possibly even when it the hard surfaces of the protective gear worn by the players. There is an eerie resemblance to the sound of a rattlesnake about to strike, and many of the carvings in the stone surfaces at Chichen Itza feature rattlesnakes. Some modern Maya interpret the flutter echoes as the voices of their ancestors, according to Lubman. Also neat info on the storm indicators there too, thanks PB!
  • Cool FPP, cool links in comments. Gracias, amigomonkeys.
  • A friend of mine did an experiment in which he recorded the sound of an atlatl (a spear thrower) in a studio, and then recorded the sound of an atlatl bearing a banner stone weight (a little rock with a hole in it; shows up in the archaeological record). He then compared the sound waves and found that the atlatl with the weight was significantly quieter. He theorized that this was used as stealth technology for ambushing (game or humans, who knows?). Sort of like the concept of not hearing the thunder until you've already been hit by the bolt, except you're not hearing the thunder at all. Very interesting study, I thought.
  • *wonders how that would work*
  • used as stealth technology for ambushing Wow! Interesting. Gotta wonder how they think thought this stuff up.
  • Wow! That was amazing! I never thought about handclaps reverberating so tightly to make a birdcall like that. It's twoo! It's twoo!