First of all, thanks to Leafcutter John for encouraging me to look into binaural recording. As a result I spent most of last Sunday designing and building a set of binaural microphones. What’s surprising is that I had everything I needed in my home. I started with a couple of old Mac computer mics that my friend Kevin gave me a few weeks ago. I tore them apart and removed the electret capsules from the circuit boards. I found a set of silicone ear-buds from an old mobile phone headset that fit the capsules perfectly. After that it was pretty easy.
On my first attempt I used the cabling from an old set of airline headphones, but the stiff wire going from the right to the left microphone was too sensitive to vibrations. After all that work I decided to disassemble it and start again. This time I sacrificed an old pair of JVC headphones. The cabling was much better and had separate cables to each driver. This time I used a paper hole punch to modify the ear-buds so the back of the capsules weren’t stuck in a vacuum. I used colored heat shrink to specify left and right, added a tiny bit of foam between the capsule and the ear-bud, then mounted a couple of layers of foam over the outside.
I was pleasantly surprised by the few test recordings I made. For the majority of the tests I placed the ear-buds into my ears and kept as still as possible since the mics are quite sensitive while plugged into the Sony PCM-D50. I ended up using the 20dB pad, although I got a better sound without the low cutoff filter enabled. For some other examples visit this post on Leafcutter John’s blog.
Binaural Finger Snaps
One of the very first tests I made using my DIY binaural mics was this example of back alley ambiance. I stood as still as possible because this first version of the headset had a stiff cable that was very sensitive to vibrations. Birds and traffic are the most obvious sounds, but there is a high pitched screeching going on throughout the recording that became even more noticeable after applying normalization. While making the recording I actually took the mics out of my ears to make sure they weren’t generating the tone and I knew I wasn’t going crazy when it turned up in the recording. The sound is either a near by train, or a neighbor using a power tool. It sounds more like a tool, but the freight trains that go through my neighborhood make some very similar sounds to this.