In the first pic as you can see, when I stand there or near the center of my base, there's this loud helicopter-like/thunderstorm-like sound buzzing out of nowhere. But as I get further from the center of my base, the sound weakens. This happened around Spring time after some heavy rains I believe. And god, the sound is very irritating because it's too loud.
Find an already established mini-area with carpets/tiles with clockwerks. Establish a base there. Wait til Spring and wait for heavy rains. Walk at the middle of the base and hear to the buzzing sound out of nowhere.