Yanny or Laurel? The science behind the audio version of The Dress

Once there was the dress; Now there's Yanny or Laurel.

This audio illusion, which went viral after appearing for the first time on Reddit, has the Internet torn. After all, what kind of monster does not hear Yanny ?

When Verge Science heard this morning, the fight between Yanny and Laurel's factions broke out. (Editor's note: I lost my head briefly, when I first heard Yanny, then I listened to Laurel for about two hours, and now I heard Yanny again, same device, same speakers, send help) ] Obviously something was happening, so we called some scientists to help us solve it. According to Lars Riecke, assistant professor of hearing and cognitive neuroscience at the University of Maastricht, it is not really an illusion. In fact, it is an ambiguous figure, the auditory equivalent of two figures in profile that also forms a vase, called Rubin's vase. "The entrance can be organized in two alternative ways," he says.

The secret is frequency. The acoustic information that makes us listen Yanny is a higher frequency than the acoustic information that makes us listen Laurel . Some of the variations may be due to the audio system that plays the sound, says Reicke. But part of this is also the mechanics of your ears, and what you are waiting to listen to.

Older adults tend to lose hearing in the higher frequency ranges, which could explain why Riecke could only hear Laurel but his eight-year-old daughter could hear Yanny ] It is a phenomenon that you can imitate in a computer, it says: if you eliminate all the low frequencies, you listen to Yanny. If you remove the high frequencies, you will hear Laurel.

Most sounds, including L and Y, which are among those in question here, are composed of several frequencies at once. So problems with perception may have something to do with that. But Riecke suspects that these overlap more in the real world than in the audio recording that is taking everyone to the wall. He thinks that the frequencies of the Y could have been made artificially higher, and the frequencies that make the L sound have been eliminated, says Riecke, although he notes that this is a speculation. Without knowing where this recording came from, you can not be sure.

So, if your sound card, or your ears, emphasize both the highest and the lowest frequency, you can alternate between the two sounds. And changing the sound mix to emphasize the higher or lower frequencies could tip it towards Laurel or Yanny. That's what it took Riecke: changing his headphones was not enough.

We also call Bharath Chandrasekaran, a professor in the department of communication sciences and disorders at the University of Texas at Austin. He told us that half of his lab listens Yanny, and half of his lab listens Laurel . But he also blames the noise of the file for the confusion. "It's a bit noisy, so the perception is a bit more ambiguous," he says. "Because it's noisy, your brain is completing what it thinks it should be."

It also points out something else: the visual message that comes with the audio, Yanny or Laurel. That could help shape what people are listening to. Here is another example of how indications shape what we hear: the same word may sound like "invoice", "cube" or "may", depending on what appears on the screen.

So it's not just your ears or your speakers, it's also your brain, says Chandrasekaran. Not only is he completing what he thinks the sound should be according to the message, it is also peculiar. What you hear – everything you hear – is shaped in some way by your previous experiences. This is more obvious with music, where training facilitates the identification of the component parts of a symphony. So just like in a noisy cocktail, your brain is completing what it does not quite a lot listen, based in part on what you expect to hear and what you have heard before.

So what makes someone Yanny listener instead of a listener Laurel ? In short, Chandrasekaran is curious, more than anything. "We're going to put together a group of Laurel and Yanny," he says. They will listen to the recording and their lab can look at their brain waves. Maybe we discovered it in a few years …