SINGAPORE - Remember the heated online debate over the colour - blue and black, or white and gold - of a dress?
The Internet has brought back another mind-boggling mystery to divide us all - this time, in audio form.
A fierce debate was sparked after Twitter user Cloe Feldman posted a four-second clip on Tuesday (May 15) of a man's voice saying either "Yanny" or "Laurel", depending on what you hear.
She tweeted: "What do you hear?! Yanny or Laurel".
And just like that, the viral clip, which has now been retweeted close to 7,000 times, has torn the Internet apart on what the voice is actually saying.
Many Twitter users replied saying that they could only hear "Yanny", while those on the "Laurel" camp insisted the same.
"I listened 10 times and can't figure out how anyone hears Laurel," said one Twitter user.
Another user tried to enlighten the masses: "If you pick up on the higher pitch it's Yanny and the lower pitch is Laurel. I heard Yanny 10 times before I could hear Laurel."
Another netizen even uploaded the audio clip and adjusted the recording's bass levels to help shed light on the mystery, claiming people will be able to hear both words being said if they do so.
However, one expert has a different take on why people are hearing different words.
The clip is apparently a result of the McGurk effect, an illusion in which people hear something different from the actual sound due to a visual stimulus.
This is even more likely to occur when the audio clip is of poor quality, Mr Raul Veiga, chief executive of production company Radial Producoes, told Buzzfeed News.
"So...it's actually a very poor quality recording and the brain gets influenced by what you read first, before you actually hear it. What gets people confused is that it's not Yanny or Laurel, it's more of a YAREL thing," he said.
He added that the device used to listen to the clip can also affect what you hear, due to the different frequency profiles of speakers or headphones.
Another theory, published by online news site The Verge, suggested that the mystery is caused by the frequencies that are picked up by your ears.
Those who are older usually are unable to hear higher frequencies, and are more likely to hear "Laurel", while those who are younger are more inclined to hear "Yanny".