How the brain gives us 'surround sound' | WBEZ
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Clever Apes #17: Deep listening

Don White captures surround sound in downtown Chicago by mimicking human ears. (WBEZ/Gabriel Spitzer)

We may not think of it this way, but we hear in 3-D. Good thing, too. It’s how we know what direction to turn when we hear footsteps or where to look for our kid in a crowded playground. But this depth of field is almost impossible to capture on tape. That’s where we come in.

On this episode of Clever Apes, we experience the mind-bending world of binaural recording. It’s an episode best enjoyed with headphones – preferably good quality over-the-ear headphones (though earbuds will work OK). The surround sound effect we demonstrate is lost when you listen through speakers.

Listen to the episode here:

And for this episode, we’re also offering a higher-quality mp3 for download.

The magic of binaural recording gets back to why we have two ears in the first place. When you hear a sound, the sound waves hit each ear at slightly different times, with minute differences in intensity and wave phase. Specific populations of neurons in the brainstem are finely tuned to each of these variables. They can also interpret the disruptions in the sound waves caused by your head and your ear flaps. All this data gets plugged into the superior olivary complex, where the brain computes the sound’s source and location.

You can replicate this effect by imitating the orientation of the human ears with special mics. Often this is done with something called a kunstkopf (German for “art head"), which is simply a dummy head with mics tucked into the ears. They look awesome and creepy. For our purposes, two human subjects – Bob Schulein and Don White – volunteered their own heads for this duty. The results sound unlike any other audio you’re likely to hear. It may be the best facsimile of what it’s like to experience live sound – it is a record of what the ears actually hear.

Bob Schulein is the founder of ImmersAV Technology. He produces HD video and binaural audio of musical acts, and was kind enough to demonstrate for us in the Jim and Kay Mabie Performance Studio here at WBEZ. Here is a sample of a performance by the Michael Anropol Trio, featuring Arnopol on bass, John Moulder on guitar and Erik Montzka on drums.

There are lots of fun binaural recordings available online, including the popular virtual barbershop. Also check out ImmersAV’s offerings here.

Meanwhile, there’s still time to enter the contest to win a Clever Apes lab coat! Submit a science question for us to answer or suggest a name for our little purple ape friend. You can leave a comment here, enter on Twitter of Facebook, or call our hotline at 312-893-2935. While you’re at it, don’t forget to subscribe to our podcast.

Bob Schulein of ImmersAV Technology shows off his in-ear microphone. (WBEZ/Gabriel Spitzer)

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