I’m beginning to study 3D audio and am having some trouble understanding some concepts. I’ve come across several explanations of ambisonics order, but it all sounds super confusing to me, especially when it comes to this image:
Does anyone have an easy/ straightforward explanation?
Ambisonics is a pretty hard thing to wrap your head around, particularly when you get deep in to the math of it, but overall its a pretty basic concept when laid out all together.
Ambisonic allows you to record and playback “3D” audio. To record and accurately represent both periphonic and horizontal axis, the microphone captures signals from all directions before being decoded to a playback array.
Firstly its important to understand, as with most other audio technologies out there, there are two ends to this tale, the recording and the playback.
Lets begin with the recording:
The most standardised/common format of an ambisonic signal at this moment in time is B-Format (4 channels: W, X, Y & Z) representing the 4-axis of a 3D space. This is derived from an ambisonic microphone (or through synthesis, but thats a tale for another day).
Ambisonic Microphones constructed from multiple cardioid diaphragms arranged in a regular tetrahedral format allow a 4-channel signal to be captured representing the 3D space, but as these are in cardioid there is some overlap where 2 or more diaphragms pickup the same vibrations at a certain location. Using a decoder, usually bespoke for each microphone, a b-format signal is derived.
Soundfield seem to be the market leaders at the moment (particularly in the broadcast industry) though this is quickly changing with a lot of start-ups offering similar products of equal or slightly below their quality at a heavily discounted price. I think there is another called tetramic? and Sennheiser have just released one too!
The b-format signal is highly malleable and can be decoded in to virtually any playback array thinkable. And this is why they are so handy, imagine recording something like a concert, and you want to create a mix in stereo/mono/surround/Atmos/binaural… its all possible from one source without worrying about phasing or weird psycho acoustic artefacts.
It’s also possible to record using an ambisonic microphone and then decode the signal to a vitrual mic, for example i could take the B-format signal and convert that into a single cardioid mic directed at a position that i see fit, this can also be used to render stereo and even surround mic configs.
Reaper is great for decoding Ambisonic signals using 3rd party decoders from manufacturers such as Harpex. Sound Particles also allows you to render files in a ambisonic format.
On top of all this you will need to be able to monitor the ambisonic signal, this requires a pretty complicated set up (at least 8 loudspeakers arranged in a cube with one loud speaker on each of the 8 vertices). A bit of a pain to set up but wow does it work.
Unlike everything your told in the audio tech industry with ambisonic playback, more IS more. the more loudspeakers arranged in a regualr array, the more accurate the directional representation of signals.
My train is almost here so i’m going to have to leave it at that for now. But feel free to ask any questions and i’ll happily respond when i’m next on here 🙂
All the best,
The “order” refers to the number of channels, and thus spatial resolution, of an ambisonics recording. 1st order is what nearly everyone is working with currently, whether it be A Format or B Format. It is 4 channels of audio. Higher order introduces additional channels and increases the spatial resolution, and is basically a catch all term for any ambisonics format greater than 1st order. This means you can get more accurate and precise sound field imaging from higher order ambisonics than you can from 1st order. I don’t know if many higher order capture rigs currently exist outside of research purposes though.
In this link you have many information to reed about ambisonic.
In this link you can download Surroundzone2 the free plugin from Soundfield to decode ambisonic in many formats.
Hope that help you!