Can you hear that? It’s like a car –idling in the distance– or a plane on a tarmac, with a tinge of oil crackling in a pan. Since the 1970s a mysterious sound has tormented communities across the globe and confounded those curious to find its source. With no recording of it in existence, and only 2 to 10 percent of affected area populations able to hear it, this hum is a sonic mystery for the ages that we’ll try to get to the bottom of in this episode.
