Binaural recording

After following a link in a twitter post by media storm entitled audio is the new video, I read for the first time about binaural sound. The link was to a blog post on where he embedded a Nike Commercial with very impressive sound.

Binaural audio is best described by the comments on the blog:

McKenzie: it is the process of recording audio in a fashion that imitates the natural way our ears “capture” audio. This includes placing microphones on either side of a dummy head, and often inside pinnae (outer ears) to replicate the unique manner that our ears take in sound. 3D for the ears.

Mike: Whilst it uses 2 mice like all the other stereo techniques mentioned, has 1 key difference. Whilst there is a slight (we’re talking a few ms here) delay due to the mics being placed slightly apart like our ears, our brains also interpret the frequency difference that the masking of our head creates. A sound coming from the left will arrive later at the right ear, but as the head is in the way, will also be missing some of the high frequency content.

For example, using this technique, recording through a dummy head (and listening through headphones) it’s possible to tell if a sound is in front, or behind, even though it may have the same distance difference between the left and right ear. The masking of our ears in this case removes a small amount of high frequencies (around 7kHz).

Binaural audio has been around for a very long time — before stereo.  I don’t think it has been used much, perhaps because it’s best experienced when listening with headphones.  Apparently a lot of iphone game have binaural audio now, which makes sense.  Most of the equipment to record binaural sound is expensive, but after searching around online, I found a DIY method here.  You can make cheap binaural-ish mics by switching out cheap headphone speakers with little electret mics.  It involves some soldering — but it’s pretty easy.  My partner helped a lot with actually creating the bigger earbud boxes with plastic and electric tape.  I initially thought it wasn’t working because I hadn’t realized that my Zoom h2n recorder had plugin-power capabilities.  I usually use xlr mics with it.  These are my new  earbud microphones:

The fun thing is that you can walk around with these plugged in your ears and no-one knows that you’re recording.  It also gives the recordings a more surround-sound feel if you’re listening has stereo headphones on.  Of course since you have the mics in your ears, you can’t actually listen to what you’re recording.  Here’s a little sample that I recorded in an elevator yesterday (there a little glitch in the middle) — remember to listen with headphones on:

and another where I was just standing at a street corner

I’ll keep experimenting and figure out the best way to use this.

Here’s a pretty famous example of real binaural audio —

And the Nike Commercial I mentioned above — not sure if it’s binaural, but it’s pretty great.


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