One of the great adventures of living in an apartment building are all the weird noises. Like at the beginning of the summer I heard this weird scraping noise, like fingernails on a chalkboard. My immediate concern was the air conditioner. Upon closer investigation I saw that it was a kid who had dug up the drip line for watering the plants outside and was dragging it across the parking lot while swinging it above their head. That would've been my second guess.
So when the new mysterious sound emerged today I decided to stray away from the obvious. I'm betting that it's a running wood chipper inside a gigantic blender.