Could We Hear the Speaking Voice of a 6-Inch Tall Human?

MetaFilter member David Provost poses some interesting questions of biology and physics:

I am considering writing a novel/story that involves the idea of people living among us who are somewhere between three and eight inches tall, but I don't know enough about the physics of sound to know if normal height humans would be able to speak to these tiny people. Would their voices be too high-pitched to hear at all, or just very difficult to understand? Would our voices be understandable to them?

How would you answer him?

Link | Image: The Borrowers by Working Title Films

I don't think it would necessarily be a matter of pitch but the decibels produced by tiny lungs pushing air past tiny focal cords would probably be pretty small. I'd say if you wanted to go the real physics approach, they'd probably be really really quiet. So quiet that few people would be able to understand them, although little kids might, and even then, it would more be a matter of distance to the ears, rather then some nature of the soundwaves "missing" our ears - tiny sound waves just wouldn't propogate through the air as readily as large ones.

But if you're going to go the hardcore biology/physics route, rather then just handwaving that aspect away, I can't imagine a tiny tiny brain, even in a tiny tiny person, would produce anything close to the cognition that we have. Insects have decentralized nervous systems, making their whole body sort of a brain, and they're insects with insect levels of cognition (not a whole lot)

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There are birds about 6 inches tall that are so loud they can be heard across the forest, so why not?

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They would sound high-pitched and squeaky like mice. And they're the same size as mice.

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I would say that this is fiction and he should postulate and develop whatever is best for his literary premise.