Gigantic, echoing chambers are a lot of fun. Ever cussed into a canyon? Neither have I, but I did it in a really big gym once and it was sick. As neat as echoes can be, however, we understand that they're just reverberating sound waves bouncing off of many surfaces. Our ancestors, on the other hand, thought they were the work of the gods.
But we're past that, right? you might say. We can't be tricked so easily.
Au contraire, my modern friend. We can, and one researcher thinks we can use these ancient illusions to make virtual reality more convincing.
Steven Waller has been studying the intersection of ancient mythology and the science of sound since 1987, and he's measured the acoustic properties of hundreds of cave art sites across the globe. According to him, ancient art was likely inspired by misperceptions of auditory illusions like concave surfaces making it appear as though sound is emanating directly from the rock, instead of another source.
To ancient peoples, the reverberating echoes of thunder in a cave became the explosive ruckus of Thor's horses galloping across the sky, or the angry shout of a spirit deep within.
Waller believes that Stonehenge, which others have speculated had musical significance to its builders, was constructed as a re-imagining of what we perceive when experiencing sound interference—when two sound waves cancel each other out, giving the perception of huge objects blocking the sound.
"I've been conducting these studies where I lead blindfolded participants into a completely empty field and just walk them around these two pipes that are droning the same note, and ask them what they think is there," Waller told me. "They all describe it as a ring of pillars, and they draw these structures that resemble Stonehenge. This is an example of an auditory illusion where they hear the sound being cancelled out but perceive it as something blocking it out."
Manipulate our other senses, and the illusion becomes a whole lot more convincing
According to Waller, the trick is all about perception and expectation. Because we know an echo is just that—an echo—we perceive it as such. Manipulate our other senses, and hence our expectations, so that we can be tricked into thinking that it's something else, say, in virtual reality, and the illusion becomes a whole lot more convincing.
Many approaches to virtual reality rely on stimuli other than visual cues to convince users that they're somewhere other than where they really are. Doctors using virtual reality to treat heroin addiction through behavioural therapy, for example, use smell to convince patients that they're really at a party with a large Hawaiian pizza and loads of pot.
Similarly, setting up concave surfaces in particular arrangements around someone being fed convincing visual cues and appropriate sounds could serve to trick someone into believing giant objects are in front of them, just like our pre-modern ancestors.
"I think that there are ways of manipulating peoples' perception to make them experience that kind of thing in a virtual setting," Waller said. "For example, if you had a scenario where there's a gigantic dinosaur, or a UFO, or a giant pillar moving across the screen, you could have a set-up that generates an interference pattern that would make the person feel as if there's this massive object walking right in front of them."
This approach would likely be costly to implement due to the cost of many concave bowls, but Waller notes that an iMax theatre might do the trick just as well. At the moment, there are no plans to exploit or easily-tricked brains' propensity for misperceiving aural cues in virtual reality, but it does make a lot of sense.
Imagine, for example, being in a virtual reality warzone and hearing bombs and bullets echo convincingly off the buildings around you, which you perceive to be actually there? Of course, I'd have to resist the temptation to have some of my usual fun with echoes: shouting obscenities my mom would be ashamed of me for.