Turns out they have a series of basically clickers that they contract and release that create resonance inside their hollow abdomen. Interesting video. And for those of you who like waltzes. The cicada sound is based off a 3/4 time signature.

Loudest they have been this year at my house tonight. Just went outside to see if maybe an ac bearing was going out. Oak tress outside my bedroom window must be loaded. I yelled but nothing changed. Don't remember them being this loud before.

You don't know loud cicadas until you live through one of the decade plus brood awakenings like are going on this year on the east coast. It's nonstop pulsing dull roar you can hear even indoors 24/7 for a week or two. Otherworldly.

It's currently happening in the midwest right now. They are everywhere and the sound at times is borderline deafening. You can hear them while driving your car with the radio going. The trees are just full of them and it's maddening. I'm so ready for them to be gone but that might not happen until the end of the month and it all started in May.