3D audio, spatial audio… What is it ?

You might have heard before someone mention that this movie you are about to watch is using 3D audio, which is obviously much better than usual stereo (left-right) sound!… But what does it mean exactly, and how does it work ?

To understand it in a simple way, 3D audio is adding an extra layer of spatiality to the usual stereo audio setup (left-right), allowing us to perceive sound with a height (up-down) and a depth (front-rear) perspective.

Sound from all directions, courses.vrtl.academy

3D audio is mainly used for enhancing the realism and immersion of movies and audiovisual productions, and will be present in most of the blockbusters that are released each summer. Although the music industry tends to have more traditional ways of working and usually keep their production to stereo, some artists like to use 3D audio to innovate in their songs, such as David Bowie in the final part of the song Space Oddity.

Thanks to the fact that new technology is always attractive to the general public, it is possible to find fabricated terms which refers to 3D audio, such as 5D, 6D, 8D music, but all these terms refer to 3D audio. In fact, even 3D audio is a term a bit gross, and in the audio engineering community, it would be referred to as spatial or immersive audio.

So to create spatial audio, is it possible to record it? Yes ! And here is one of the most universal technologies that is used to achieve it: Ambisonic.

(Note: Ambisonic is not the only method used to make spatial audio).

Ambisonic is a method invented in the 1970’s that enables one to capture an entire “soundfield” perceived from one center point. Ambisonic sound is stored in terms of spatial coordinates; the advantage that it offers is that it can be listened back through any reproduction system, from headphones (called binaural) to humongous speaker arrays, such as in a modern cinema room with 50+ speakers. Although ambisonic is not the only method to record/create spatial audio, it is a cheap/efficient technique that has been approved by a lot of the media industry.

However the spatial resolution isn’t always perfect, and without getting too technical, it can differ with certain types of ambisonic microphones. The most basic ambisonic microphone, such as the AMBEO VR Mic will use four capsules that will each capture an angle of 90° of the soundfield, for a total of 360°. It is referred to as First Order Ambisonic (FOA).

But there are more accurate microphones that can use a lot more capsules to capture even narrower angles of the soundfield, such as the Eigenmike microphone that uses 32 capsules. It is referred as Higher Order Ambisonics (HOA) and in this case, 4th order Ambisonic.

Here are some examples of FOA audio recordings.

Here are some examples of HOA audio recordings.

Waw that was technical ! Anyway, what are the cool applications that ambisonic has to offer us ?

A very big customer of ambisonic is virtual reality (VR). For VR, it is crucial to have realistic spatial audio to create immersive games and experiences for the users. For example, if you play a horror game in VR, and there is a jump scare coming behind you but the sound is not coming from exactly the same direction, the scare effect will not have a good impact and it will deteriorate the experience.

One VR application that I strongly believe in is the virtualisation of live music performance, and for this to be a successful new entertainment concept, the integration of spatial audio is an absolute necessity !

Now what about spatial audio usage with the Abbey VRoad Studios project ? Well it will be used in the experience to engage the musicians more deeply in the virtual studio! More details will be available later on in the year as it is still in development, but if you want to find out more about it, please feel free to contact me.

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