The Great Hum or Just the Hum?

Frog Daddy writes to talk about Sky Trumpets, which some tend to lump into the theory of the worldwide hum. He says he's never heard this sound except through video and it gives him goosebumps. Is the world crying out in pain? Let me see that in the Werner Herzlog voice. Are angels signaling the end of times? Could it be construction machinery or could it be the stuff they don't want you to know?