Binaural recording can be used to imitate the human hearing using a pair of stereo microphones placed in silicone ears on a dummy head.
The time difference between the sound hitting ear A, going around the head and hitting ear B is what makes this work so well.
For more info Wiki binaural
In this Instructable I will show you how I built my binaural head. The head consists of 3 parts; the base, the head and the microphones.
Step 1: Material
1, A styrofoam block (bigger than a head)
2, An old hair dryer (or nichrome wire)
3, Filler (putty, spackle)
5, Silicone (The one I used is made for make up FX work)
6, Black dye pigment
7, Spray paint
1, Sheet metal
2, Threaded inserts
1, 2pcs WM-61A Electret microphone capsule
2, Shielded two conductor cable
3, 3.5mm stereo jack (1/8")
4, Shrink tube
Step 2: Tools
Knives (for carving)
HSS drill bits
Step 3: Building the Head
1, I started by sketching out my design in scale on a piece of paper.
2, Then transferred the design to the styrofoam block.
3, I then used my hot-wire foam cutting nunchucks to roughly cut out the shape of the head.
4, I continued cutting away foam until I could see something that resembled a head.
5, The putty I used actually dissolved the styrofoam a bit. So use something that is meant for dry wall or wood and not cars, like I did...
6, Sand, sand,sand,sand,sand,sand until smooooth.
7, Use a hole saw to cut out the holes where the ears go. Also make a hole up the neck for the base to fit.
Step 4: The Base
Unfortunately I didn't take pictures of the build here but it's a simple design. Just cut out and bend some sheet metal and weld it to a circular base plate the same diameter as the neck of the head (I don't know how to weld myself, my colleague helped me).
Sandblast (not necessary).
Paint it black.
Step 5: Ears
1, I made the negative casting using alginate. Alginate is water based and does not stick to hair. USE EARPLUGS! A vacuum will form in your ear when you try to pull the alginate out. This could damage your eardrum.
2, Dye the silicone with black pigment dye.
3, Mix part A and B thoroughly.
4, Pour the silicone into the alginate casting and let it set.
(My results could have been better. There's too much pitting in the silicone. I think the alginate might have started to dehydrate and pushed the water out forming little droplets inside the mold.)
5, Cut the outside of the silicone ears to fit inside the hole saw used tho make the ear holes in the head.
6. Make a hole through the ear going inside the head. Pretty much an ear canal. This is where the microphones will go.
Step 6: Microphones
No pics in this step! Check out DJJules excellent instructable on how to Build Lavalier or Lapel Microphones!
What i'm doing here is the same as his stereo version.
1, The shielded 2 conductor cable has 2 conductors and a shielding.
2, Solder 1 conductor to each microphone and use the shielding as the ground for both microphone capsules.
3, Use the heat shrink tubing and some hot glue to make them more durable.
4, Solder the 3.5mm jack to the other end of the cable and make sure none of the internal tabs are shorting out.
It plugs straight into my PiP (plug-in-power recorder).
Step 7: Done!
Look at that!
All that work made the result look great! You could just use a doll head and some microphones but hey, where's the challenge in that.
Thank you for reading my binaural head instructable! If you liked it, please check out my other instructables here!
Sound demo below.
A word about the Linkwitz mod.
I know these mics can be modded to get a higher SPL. The downside of the Linkwitz mod is that the SNR get worse. Since i'm not going to record anything extreme with these mics i went the unmodded way to get better recordings with better SNR.
Stay tuned though because I'm planning to build a lavalier mic using the Linkwitz mod in the future.