Where I live, we have recently been overrun with the infamous Brood X cicadas. Cicadas make a very loud sound to attract other cicadas for hot cicada lovin'. It basically sounds like a cricket on speed with a megaphone. When all the cicadas get together and sing their song (which they do all the time) it makes a sort of diffuse, high-pitched drone which sounds exactly like the flying saucer sound effect from a 50's sci-fi movie. I keep expecting to round the corner and find a big shiny robot made of tinfoil or an alien wearing goggles and flippers who will demand to be taken to my leader or turn me into a pod.