An insect called the water boatman can make loud noises with its genitals!

The water boatman is only the size of a flea, but it can produce a sound as loud as a lawnmower. This loud chirping sound is actually the sound of the male’s tiny penis rubbing against its abdomen. The sound is so loud, that scientists were convinced that it had to have been coming from a different bug when they first discovered it. This creature is now the loudest animal known to man.
(source)