How to build a dummy head for binaural recordings
Spatial sound is something I’m very excited about, especially the fact that one can create a fictional 3D sound environment that feels real is just awesome to me. After reading a lot about 3D sound, VR sound and ambisonics, binaural recordings, and everything in between; I decided to build a dummy head for binaural recordings because ideas of what I can do with it haven’t stopped flowing.
Binaural sound is a reproduction of sound the way we hear it. Since our birth we are trained to localise sounds according to the interaural time difference - the time difference in reception of a sound between two ears. Both ears also receive a different intensity and frequency spectrum of a sound, all because of the shape of our head and ears, which cause a sound shadow.
(For more on 'Head related transfer function' click here for Google search results.)
Binaural audio needs to be played back through headphones for the listener to be able to have a 3D sound sensation. But there are some challenges that come with that... We come in all different shapes and sizes and are therefore used to our very own and unique HRTF. This means some might have difficulties to localise a sound position from binaural recordings precisely. Especially regarding whether sound comes from the very front or back can be tricky at times.
However, the result we get by recording with a ‘binaural dummy head microphone system’ is quite cool. Judge it for yourself in the video.
To record a sound in the way we hear it, I needed to put two microphones in a dummy head’s life-like ears. Firstly, I bought a styrofoam mannequin head on Amazon for £10.83. I know that styrofoam is not the best material for emulation of the sound absorption and diffusion of a human head, but I went for a cheap option, which I still think works relatively well.
The shape of ears was very important, because I wanted to replicate a sound shadow it creates. I found life-like silicon ears for £14.90, which were made for acupuncture training purposes. Good enough. I dug out some space from the masculine head for the ears to fit in using a trimming knife.
Silicon ears needed to be pierced to make space for microphones, I did that by a drill. Microphones should be in as deep as possible, so that pinnae could reflect and absorb the sound at its best. I dug tiny canals into styrofoam on the dummy’s neck to secure the cables and make them steady so they wouldn't produce any unwanted noise.
The silicon ears sat quite nicely and wouldn’t move, but just to be sure, I taped them and cables with sellotape to keep them in intact. I also tried to emulate the sound absorption of an upper body by putting a pillow underneath the dummy head. I was hoping that this would improve a vertical sound localisation.
As I want to carry this thing around, I needed a handle. I didn’t really bother about the looks, so I just took a wire hanger and tape it underneath the pillow. Looks horrible - I know, but it did the job.
All in all, a simple dummy head for binaural recordings is fairly easy and cheap to make. I haven’t had a chance to compare it with the professional one yet, I hope I once will. I already have lots of ideas of what to do with the one I built - I’ll share more on my future binaural projects soon. I’m quite happy with the finished result, but I know I could do better - not just aesthetically, but also in terms of better build. However, mission completed.
Put on your headphones, click here and take a stroll through he busiest street in Edinburgh.
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