They probably just left, there were many people going to those shows just to check out Sphere and it's the in thing to do. I saw people like that when I went. That's always going to happen at that place and in Las Vegas.
Of course it could be that the visual effects bothered them or they weren't feeling well or had some sort of emergency, you always have to consider possibilities like that.
I didn't even notice my ears not ringing, but now that I read it here yes indeed that's incredible. The sound there is superb.