The cache is not at the listed coordinates.
About 5 years ago, I heard a low, pulsing droning sound each night as I lay in bed. This carried on for several weeks and then disappeared and has never returned. I don't know what caused it but perhaps it was someone running electrical equipment nearby or much more likely it might have been space aliens scanning the neighbourhood for humans to abduct. Come to think of it, maybe I was abducted and all memory of my abduction was erased....
This puzzle is about strange sounds, some of which have known causes and some of which are just strange. Leave out the word "the" where it appears in the answers.
Begin the puzzle here.