I have gone back to it again and now I head laurel. I think it it two different clips and you just get one at random when you click on the link.
It's definitely the same clip - my partner and I listened to it together and I heard yanny and he head Laurel and then a group of colleagues and I all listened together and it is a real split!
Apparently the 'yanny' is pitched higher so older people or people who don't have such good hearing are less likely to hear yanny and more likely to hear laurel.