While you could be forgiven for thinking that surround sound, such as that heard in the cinema is immersive, in the context of sitting staring forward at a screen, it is. However, that is not quite the same as binaural sound in the context of the real world. VR is striving to creating realistic three dimensional worlds visually and sonically, which can’t be portrayed convincingly by 5 channels of surround sound audio, especially when the person is free to move and face any direction.
Three Dimensional Hearing
As a human we can tell where sound is coming from. In a real world environment you can tell whether sound is above, below, behind, to the right, in the distance and so on. Despite just having two ears we interpret sound in 3 dimensions.
For example, picture the scene, you are walking down a woodland path, ahead of you there is a stream, behind you there are workers in the distance using hammers and chainsaws, and around you there is bird song. Despite only having two ears you know where each of the sounds are coming from. Also, as you move, the sounds change and if you turn around 180 degrees you will hear the stream behind you and the workers in front of you. This is a biological and scientific miracle that we pretty much take for granted. In basic terms our heads, the shape of our ears, the environment, the speed of sound and how it arrives at different places at slightly different times and our brains amazing ability to decipher all of this create the real-time binaural world that we hear every millisecond of every waking hour.
Recreating such complexity and having it change in the same way when we move our heads is rather challenging and not really possible with speakers currently. If you think of it, every sound in the example is its own sound source, if we were to replace each of them with a tiny speaker we would need a vast number.
For fun, I play the trombone in a big band with about thirty players. When sat playing or listening in the middle of the band the experience is truly immersive and I would say that experiencing that live with sound emitting from 30 players and interacting with the environment is totally immersive. Listening to a recording of the same band seems flat in comparison.
Recording in 3D
The closest we seem to be to experiencing binaural sound as it is intended is via headphones only. This is because each ear is isolated and hears only what it should hear. Playing it over speakers causes bleed, which means you will hear a mix of the left and right channel in both ears compromising the binaural effect.
Binaural recording goes back many years, and the early options used a dummy head that contains two microphones in the ear locations. This is to emulate the way sound waves interact with the structure of the head and the shape of the ear so that sounds wrap around the head as they would for a real person.
There are modern versions of this recording setup. From a personal point of view, I wonder how a hard bald plastic head can compare with a real person’s head with hair.
A more modern version of this can be found at 3dio, although it seems that they have disposed of the head and have just created the ears with a soft latex type material. The Verge have done a great video using this. See references below.
When the word binaural is mentioned many people think of music productions for wellbeing, relaxation and spirituality. To avoid confusion this is the difference.
Binaural beats are created when a pure sine wave of one frequency is played with a frequency that is close but not the same. This creates a beating effect in the head when one frequency is played in one ear and a differing frequency in the other ear. Heard in isolation, neither frequency has beats, but together they do.
By beats, we are talking more about a tremolo or vibrato or warbling effect on the sound, nothing to do with drums.
The different frequencies are said to create brain states that help induce certain states, such as relaxation, sleep focus etc.
Conclusion and personal view
I find the whole subject of VR and 3d audio fascinating both from a technical point of view and an experiential one. However, while I think technology will improve this over time, I still think that having to wear headphones makes the experience feel and sound unreal. I guess the isolation and direct sound make the experience fake. Let’s face it, you never forget you are wearing headphones. For me, it will be interesting to see this technology improve over time and how it will overcome this artificialness of headphone sound. Perhaps, we never will recreate the spaciousness of natural sound and will have to adapt VR audio to work over massive multichannel speaker arrays and rely on our ears to do what they do naturally. I guess I am dreaming of a holodeck from Star Trek 🙂
In terms of the microphone, there has long been stereo recording techniques where two microphones are used as a pair at 180 degrees from each other. This does not benefit from the presence of a fake head or fake ears, however, I wonder how much this actually adds or detracts from the effect. Perhaps I need to try a few DIY binaural recordings very soon.
Please feel free to comment and share!
References and Further Reading / Viewing
Interesting videos using 3dio
Binaural Beats Generator
Post about the holodeck with interesting videos about VR
Binaural recording Wiki