A week ago, this passage appeared in an article about timing and the brain:
If you’re hiking through a jungle and a tiger growls in the underbrush, your brain will instantly home in on the sound by comparing when it reached each of your ears, and triangulating between the three points. The difference can be as little as nine-millionths of a second.
As if people had three ears. “Triangulating between the three points” is gibberish. The between-ear time-of-arrival comparison gives you a direction, not a location (which is what triangulation does). Perhaps it was added by a copy editor. If you delete it, the passage makes sense.
Wouldn’t that make a nice newsbreak (one of The New Yorker’s column-ending “Funny Usage Mistakes Made by Other Publications”)? I tried to submit it but couldn’t. So I wrote a Letter to the Editor about it.
In this week’s issue, Hendrik Hertzberg, the magazine’s main editorial writer, calls the idea that “global warming is a hoax” a “denial of reality”. He lumps it with birtherism and the ideas that “evolution is just another theory, on a par with the theory that the earth is six thousand years old.” In case you are reading this blog for the first time, I’ll say it again: Claims that humans have dangerously warmed the planet are based on climate models that are far from fully verified. That these models manage to fit past temperatures means little because the models have many adjustable parameters. Alas, this was no over-zealous editing mistake.
Here’s another example: Here, a skeptic of psychotropic drugs talks about being compared to an AIDS-denier.
sounds at different heights will reflect on different parts of the ear, and that will modulate the sounds a bit. the brain can absolutely tell the height of a sound and therefore the direction. you can call that triangulation if you want; i bet the algorithm is like it.
The reason bats have such weirdly shaped ears is exactly as q describes. There’s a whole chapter devoted to them in The Blind Watchmaker.
A tiger’s growl is low-frequency enough to do the phase difference; high-frequency sounds don’t refract around the head so well, and the brain does amplitude difference instead. Mid-range sounds are harder to locate.
Figuring out the direction from which a sound came narrows down the location of the sound source to a line. Triangulation narrows down the location of the sound source to a point.
I thought triangulate meant to form a triangle, the two ears being two tips of the triangle and the origin of the sound the third point.
To increase hearing sensitivity, a technique I learned was to open my mouth wide, and look at where the sound was coming from. I haven’t tested this with rigor, but it seems to work. Opening the mouth seems to give me a more specific location on the vertical axis of origin.