Hearing things

Sine-wave speech is the sound that results when you take a recording of speech and strip it down to a few wavering tones. The result has little in common with real human speech, but if you know what to listen for, you can actually "hear" words behind the whistling. Listen to a demo here; the effect is most powerful if you listen to the sine-wave speech first, then the normal sentence, then the sine-wave again.

The same pattern-seeking ability which helps us make sense of distorted speech can cause us to hear words where none exist. Richard Dawkins writes:

Once, as a child, I heard a ghost: a male voice murmuring, as if in recitation or prayer. I could almost, but not quite, make out the words, which seemed to have a serious, solemn timbre. I had been told stories of priest holes in ancient houses, and I was a little frightened. But I got out of bed and crept up on the source of the sound. As I got closer, it grew louder, and then suddenly it “flipped” inside my head. I was now close enough to discern what it really was. The wind, gusting through the keyhole, was creating sounds which the simulation software in my brain had used to construct a model of male speech, solemnly intoned.
Had I been a more impressionable child, it is possible that I would have “heard” not just unintelligible speech but particular words and even sentences. And had I been both impressionable and religiously brought-up, I wonder what words the wind might have spoken.