This show started out interesting, but drifted and then plummeted into the arrogant and absurd. And, I'm one who loves the idea of preserving unspoiled natural spaces.
That said, calling silence an endangered "species" is similarly absurd to some social activists who a number of years ago described the population young black men as an endangered species because of violent crime. Neither is a species and in both cases the dumbing down of the word use just feeds into science ignorance of an intellectually lazy public. The absence of unnatural noise is a CONDITION.
Even worse, should we accept Gordon Hempton's ridiculous arbitrary and arrogant distinction between the rumbling noise of a passing freight train and the distant noise of tires rolling down the interstate because HE likes the sound of train whistles? He described it as a "message". The honking sounds of taxis in midtown Manhattan are also a message, i.e. "Will you get moving *#&%!!!". He, Hempton, might not like the message but it's the same message as the engineer telling anyone at the RR crossing to get out of the train's way. As soon as we make arbitrary, emotional "because I like it" distinctions between good noise and bad noise the conversation about natural and unnatural becomes a non-starter.
More information about text formats