It's not like there isn't plenty of research showing how bad open plan offices are. Not only less productive but for employee health as well.

I think it's also not just the volume but the type of noise as well. At my last office, the noise level was higher which was distracting, sure. But a lot of it was crates being dragged along the floor, heavy boxes being dropped - ocassionally people shouting. It was annoying but nowhere near as stress-inducing as being surrounded by people talking. And not just the noise but also the people are draining for an introvert.