I've seen something that some people would call a ghost.
Did you already post that somewhere? If not, please do. And what would you call it instead of a ghost?
You know I think not even wrong is not even wrong to assume a perfectly explainable source for these "voices", even if it seems he hasn't put this theory to the test.
Sorry about the pun, not even, but I think you'll hear that more often. On the one hand, voices and murmuring has often been reported in alleged hauntings, on the other hand, I think it has been shown that some surfaces can resonate with radio waves and produce sound if an emitter is in the vicinity. Did you hear anything that would point clearly to a radio or TV programme, like music or jingles?