When I heard them as a kid in New Jersey (I think the early 1960s, but I can't find a record of past outbreaks) what impressed me was how their racket came in waves. There'd be a few moments of silence, then it would start and build, as if they were all answering each other. Then another respite after a few moments, until the call would be taken up again.
I also remember their molted exoskeletons being all over the trunks of the Japanese cherry trees we had in our front yard. But I don't recall many of them being airborne adults.