What are cicadas saying?

The other day I was mowing my yard and heard several cicadas “talking” to each other. I suppose it was talking. It definitely wasn’t singing. It seemed like a lot of noise. And it was LOUD! Just how loud are they when I can hear them over my lawnmower?
I wondered what they were saying to each other. They’re probably calling out for a mate. But what do they have to say? My guess is, “I’M IN THIS TREE!” And then another responds with, “I’M IN THIS TREE!” (Yes, the uppercase yelling is appropriate here, because they are definitely screaming.)