It's like the black and blue or white and gold dress, but in audio form.
For the past 24 hours it has been doing the rounds and confusing everyone.
If you've missed it have a listen to this...
What do you head? Yanny or Laurel?
The Science Part:
Speaking on Radio X in the UK, Kieron 'The Science Teacher', told host Toby Tarrant that it's all down to a thing called "perceptually ambiguous stimulus", where our brain interpenetrates something one way or another.
There's two differently pitched pieces of audio playing, one which is high and one which is low.
As these play out at the same time and the same volume, your brain just chooses one to listen to.
See it in action here....