DIY "Binaural" Dummy Head
It is finally done! The binaural microphone + Dummy Head project has come to a successful end; it has been an exciting experience crafting and soldering this thing together from scratch - I must admit that I have learned a lot from it and I am also excited to be creating more of these practical gadgets in 2017!
Ever since listening to the Virtual Barber (https://www.youtube.com/watch?v=IUDTlvagjJA) I have been very keen to understand and delve in this technology and what it can do. The 3D effect that binaural recording creates is so mind blowing and makes certain things sound so much more realistic - it just had to be explored.
For those that aren't familiar with the concept of Binaural recording, it is basically a simulation of our human hearing by accurately recreating the physical "colouring" that sound undergoes before it reaches our inner ear. The main key physical factors that influence sound are mainly:
-The Shape of our Pinnae (external part of our ear)
-The Physical Barrier between the left and right ear (our skull) and its form
-The Shape and length of our Inner Ear
-The frequency range of our hearing (different from person to person)
In order to accurately recreate how we actually hear I needed to apply these factors to my Dummy Head model.
In this next part I will show you Step by Step how I went about making the Binaural Dummy Head:
Step 1: Human Head model in Autodesk
I had some help from my Industrial Designer friend Martina who had suggested that we find a good 3D model of a head and use it as the base for the dummy head. We simply imported it into Autodesk which is a free 3D modelling software.
We found a good looking model and were able to "slice" it vertically into about 20 layers - something that turned out to be super handy later on.
Step 2: Print out "Blueprints" and Cut the Foam
Next we got the layers printed out on A1 sized paper (A3 and A2 turned out to be too small) and cut out each layer. We went to a local Foam store and got a 2 squr. meter piece of 10mm thick foam which we used to form the head. We traced the paper blueprints onto the foam and cut out the foam layers with a utility knife. Then we glued all the layers together to form the head.
Step 3: Microphone and Cables
In order to actually capture the sound I ordered a DIY kit from a UK based company called (www.micbooster.com). I ordered the EM172-Z1 capsules + 3.5mm jack connector + 1.5m shielded cable kit. Along with that I also used an old pair of headphones for the frame of the microphone but you can also attach them straight to the foam head.
Step 4: Soldering
This part was a bit daunting for me as the EM172-Z1 microphone capsules are apparently very sensitive and could be damaged if subjected to excessive heat. I used some foil to absorb some of the heat while soldering.
The soldering was a bit messy but was a fun practical step (don't inhale the solder fumes when soldering, it isn't healthy :P). At the same time I had thought about adding an alternative option to connecting the microphones. Since the kit only came with the 3.5mm connector I had to make a plan to convert it to a XLR output so that I could plug it into my soundcard.
Step 5: "DI" box
I bought a small plastic container, drilled two holes for 2 Neutric XLR male connectors to fit in and did some funky electrical engineering based off another DIY website in order to be able to use the microphone with 48V phantom power.
Funky Electrical Engineering part:
https://tombenedict.wordpress.com/2016/01/16/powering-the-em172-capsule/
Step 6: Capacitor, Resistor and Multimeter
The picture on the left shows the inside of the DI Box after Step 5: The left part of the box is the 3.5mm connector that splits into 2 cables that are connected to the 2 male XLR connectors (on the right). The XLR connectors each have 1 resistor and 1 capacitor soldered directly onto them to reduce and control the input Voltage. I used a multimeter to see which side of the connector was ground, neutral and live and to see if the resistors actually worked. (This was an important measure because if your resistor isn't reducing the incoming voltage then you can do irreversible damage to your microphones)
Step 7: Headphones and Silicone Ears:
Along with the binaural kit I also bought a pair of silicone ears from the same company (micbooster) which I used as an accurate representation of our ears.
I then butchered my headphones by taking out the electronics and then cutting off the ear parts and finally turning them around to face outwards (see left)
I made a hole at the back of the silicone ears and stuck both microphone capsules inside facing towards the outside of the ear. The ears luckily fit snug inside the ear piece of the headphones and I simply took some safety needles and the fabric cover of the headphones to hold the ears in place. The headphones are simply put on the dummy head and can even be taken off to be put on your own head if you wish to record yourself jogging!
Many thanks go to Martina for her help with the crafting of the head and Timon for his drilling skills!
I will upload some samples of the binaural recording sometime next year so stay posted!
