Introduction: Binaural Head for Stereo Recording

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.

Instructables that inspired me and helped me realize the project: Hot-Wire Foam Cutting Nunchucks by radioape and Build Lavalier or Lapel Microphones by DJJules. Thank you!

Step 1: Material

HEAD

1, A styrofoam block (bigger than a head)

2, An old hair dryer (or nichrome wire)

3, Filler (putty, spackle)

4, Alginate

5, Silicone (The one I used is made for make up FX work)

6, Black dye pigment

7, Spray paint

BASE

1, Sheet metal

2, Threaded inserts

3, Bolts

4, Washers

MICROPHONES

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

Pliers

Soldering iron

Knives (for carving)

Drill

HSS drill bits

Hole saw

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.

8, Paint

9, Done!

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).

Clean it.

Paint it black.

Step 5: Ears

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.

Step 8: Misc Pics

Comments

author
dgateley (author)2016-05-29

You've inspired me to take a new look at an old problem that halted some promising investigations a while back. I actually need to get a casting of my full ear canal including the ear drum. Tricky deal, that. I'd been using a silicone casting material to capture my canal and an otoblock to stop it just short of the drum. Close, but no cigar. My project is to capture the precise characteristics of my ears so that tiny Knowles mics placed real close to my ear drum become recording devices that I can use with measurement and subsequent DSP to capture all kinds of things and transform them into other realistic things with very high fidelity and verisimilitude.

The silicone models I've been using are imperfect near the eardrum and that creates serious repeatability problems which is the bane of this work. Bane enough to have halted progress for damn near two years because I was unwilling to risk my ear drum to pressure detachment using silicone.

What I am going to do based on this article is use the molds I have to work out an alginate mix that sets up with the right characteristics and then use that to cast the full length of my ear drum. The right characteristics include the ability to extract it intact from the (airtight) silicone mold with the ability to break the seal somehow to spare the drum. Should there be extraction difficulty, any residue is easily removed by a water flush. That way I can monitor and respond appropriately to over-pressure at my drum and abort with flush if need be.

Thanks for spurring me forward.

author
wobbler (author)2016-05-28

Great Instructable, I'm pretty sure I know
him. It would be interesting to compare recordings made with this dummy
head and two seperated microphones without the dummy head.

It's
also slightly cheaper than this version at £6,260.85, which would bring tears to your
dummies eyes if it only knew how much it was worth (and if it could
cry-maybe another project?):

http://www.dolphinmusic.co.uk/recording/microphone...

As a further aside, it would look awesome using an Easter Island head shape, although you might find getting a block of styrofoam big enough a problem. I suspect it would be slightly lighter though than originals at least and therefore slightly more portable, plus if you made it life size we'd then know what it was like to hear like an ancient god.

author
DJJules (author)2016-05-27

Awesome build! I've always wanted to do this and never got around to it.

Jules

author
arthurjohnson (author)2016-05-26

this is sooo cool actually, the idea, the style. and very well executed

About This Instructable

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Bio: I am a sound designer who's studied computer game development, run my own sound design business and like to build thing in my spare ...
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