So, much like the black and blue vs white and gold dress debate of 2015, the internet was divided once again yesterday when some people hear Yanny and others heard Laurel. Let us explain…

It began with a simple tweet.

Obviously the voice was saying “yanny,” but some people heard “laurel”? Like… what? There’s not even an L in that sound byte! But on the other hand, there actually is.

The effect is achieved by layering two pieces of audio on top of each other at different frequencies. Based on the level of bass coming out of your speakers as well as your genetic disposition to certain frequencies, you might hear either “yanny” or “laurel.” Considering those words consist of entirely different English phonemes, it’s actually quite fascinating.

You can see how the effect is achieved below from @earthvessquotes, as well as demonstrations from Ghastly and Boombox Cartel.