What is far more common is people, and in this case 6 of them, actually hearing a voice when it speaks. Happens everyday all around the world. People are good at discerning voices, and they're good at telling what direction they come from and how close they are. Your claim that they were hearing some other noise and projecting vocal properties on it is not supported by the audio nor by the eyewitness accounts. As usual it is mere speculation based on the faith-held dogma that the paranormal can never occur. It is almost a religious fanaticism for you, this unflinching belief that the paranormal can't happen. Curiously enough, nothing in science actually forbids it. We already admit the probable existence of other dimensions. There's nothing in science that entails those dimensions can't be inhabited by other intelligences.