How do cicadas make their signature sound, so eerie and amazingly loud?

BY SETH BORENSTEIN
AP Science Writer

WHEATON, Ill. (AP) — What stands out during a cicada invasion is the sound. It’s a constant, eerie, amazingly loud song that gets in a person’s ears and won’t let much else in. And it’s coming from the tiniest bugs. The song comes only from males, and it’s a mating call. The way they do it is a lot like how a drum works. They have a white membrane on their midsection that is made to vibrate. Then with some air behind it to make a good echo chamber, it creates a loud sound. If you listen carefully, there are two types of basic cicada calls. One is a buzzy wave that goes up and down, and the other is a constant whirring hum that is punctuated by a sound like fffaaaro, fffaaaro.