Holy cow! This blew my mind.
When I first played the sound, in the “middle” position, it sounded so much like “Yanny” that I could not imagine anyone possibly thinking it was “Laurel”. Even as I slid towards Laurel, it still sounded like Yanny, until I finally hit Laurel, almost at the end of the slider.
But then I could slide it almost all the way back to Yanny and still hear Laurel. The same sound sounded different to my brain depending on what I most recently heard. This is clearly a dynamic system.
It’s also clear that the Yanny and Laurel sounds are different frequencies.
I suspect this is a similar phenomenon to the “hello?” phone answer — it exists to prime your brain to understand the voice on the other end of the line. Hearing a particular voice primes you to pick out that voice from the noise. So once I started hearing Laurel, I was primed to hear the Laurel-speaking “voice” in the original sound.
Reminds me also of the McGurk effect.