I heard yanny the first few times, then it switched to laurel and I can't switch back.
The sound is not identical to what you'd hear if someone said either word. Therefore your brain does some 'translation/filtering' to get you to something mildly recognizable. When that filtering tends toward the higher range of the frequency in the clip you get yanny, and lower end gets laurel. Or something like that. That's my guess at least.
I'm sure there will eventually be a breakdown by one of the educational YouTube channels on the topic that will explain it much better.