Binaural sounds are almost like what we hear with natural source. If someone says hi behind us and we record audio in mono, stereo and binaural the best output with realism is recorded in binaural. This article makes a basic quality binaural recorder. The quality is not great because of limitations and manual steps required causing further inaccuracies. You can check the sample quality at end of article to check what it feels like.
As picture above shows we need 2 audio recorders. I used 2 Samsung devices with same official recorder app. Phone acts as left ear and tab acts as right ear. MIC are at top of the devices and therefore top is kept at middle of a box. Box acts are head reducing audio from both sides. Recording on both devices should begin at the same time!. If recording time is not same on both we have to shift the playback timing of one track to match both tracks.
IMPORTANT:
2 recorders must be of same hardware/model, same software and same settings to get same audio data. Different devices can work but many times volume levels & dominating frequency can differ e.g. high frequency/volume on left, lower on right etc.
When recording is done below steps are to be done to create final sound.
- Start Audacity app.
- Import Left audio recording from whatever device acted as left. If imported file is stereo it has to be converted into mono. Audacity can do that easily. Now this mono track should be set to Left Only track. There is a slider to set panning between Left and Right. Slide it to leftmost.
- Same as above right track is imported. Slider is shifted rightmost.
- Now Check the waveforms and using this the shifting of track can be done to match the timing issues happened during starting of recorders. Suppose started recording with a clap. Using the clap as reference we can do shifting of Left or right track until the timing error caused during recording is diminished.
- NOTE: Lets assume both track have been set to perfect time match i.e. a sound is heard at both ears at same time. This is actual wrong setup for binaural!. When sound comes from right it reaches right ear first and then left. The time travelled between right left ear MUST EXIST between the tracks. This is important for accuracy of audio source positions. Below is technical information and can be avoided if you cannot understand the topic but it tells the importance of time difference between Left and Right.
https://en.wikipedia.org/wiki/Interaural_time_difference
https://en.wikipedia.org/wiki/Sound_localization
After shifting of tracks sound can be tested and it will surely sound like binaural. The above method is very cheap and prone to lots of errors. This article is for giving understanding of binaural and some experimentations for advance work. Below is the recording I created.
Sample recording file:
https://drive.google.com/file/d/140yaOUVX4ptCyBduURUFXzGjx3Nrwl7o/view?usp=sharing
I hope this article has helped you in binaural recording. I also made an Android app in 2016 with automated process and create binaural recording easily. However I could not keep developing the app. Below are some links to the app -
https://forum.xda-developers.com/t/binaural-3d-sound-recorder-app-using-2-devices-as-mic.3361953/
backup apks for old android devices only. -
https://drive.google.com/file/d/1PP1N1HsOfLVqaMEMj77g0giLON9ecNuV/view?usp=sharing
Sample i recorded using my android app
https://drive.google.com/file/d/1PftsM9XHOUJB8vzL4cB4vUV5mGZ-28v3/view?usp=sharing
