How does my ear differentiates, that it’s the TV sound and not my neighbor being slaughtered?

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So when I pass by my neighbor’s door, and I hear the noise someone bleeding in the movie makes(no music, no suspension sound effects, plain pain moaning), I initially know it’s a movie.

How? What exactly makes the sound of a person moaning from pain different from an actual person moaning, that doesn’t make 1000’s of false alarm 911 phone calls everyday all around the globe?

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3 Answers

Anonymous 0 Comments

Human ears are incredibly good at locating sounds in three dimensions, subconsciously, including tone and time shifts from echoing off of surfaces, and combining that into a mental image. While it’s not unique to humans, it’s still a fairly unusual ability in the grand scheme of creatures with ears.

There are a few clues your brain uses to determine that it’s not real, and given a high enough quality setup you can actually reproduce these for yourself, it’s pretty fun. In no particular order, some of the bigger ones are:

* Most speakers have a more limited range of sound than actual human voices, so you hear missing tones
* The locations from a pair of stereo speakers tell you that it’s two sources, not one, and therefore not real
* Human voices don’t radiate like a speaker, so the echoes are wrong
* Some recording media lack dynamic range and frequencies compared to a human screaming – especially older media

Now if you correct for all of those – big high quality speakers, a good recording, and position yourself so that the multiple speaker sources sound like a single location, and suddenly it sounds real. And that’s how a good home theater works.

By the way, there are some false 911 calls from this still. 🙂

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