I respect the rigor here, but I can't imagine "scary scream like noise was used to spook people" is a novel idea to anyone. The main interesting point to me is that it was categorized as both manmade and non manmade. If you wanted a scream you could just make one yourself. So I suppose the utility of the instrument is that the scream sounds human like but obviously isn't, adding some fear of the unknown into the mix?