While rereading this I had a somewhat terrifying thought. Steel is a very durable material, and I wouldn't be at all surprised if it could, under the right conditions, act as a sound recorder. (I don't know if this is true. I'm merely speculating.) If such a thing were possible, can you imagine what the steel from the WTC might have recorded during it's fall? Then, take all of that steel and transport it to a dump site, piling it up willy-nilly and wait for just the right temperature change, or just the right tremor in the earth. Imagine what a nearby listener might hear if the steel were to suddenly begin screaming!
I'm not sure I'll be able to sleep tonight.