Technical Notes

Technical notes on Higher Order Ambisonics and related subjects.

HOA Technical Notes - Introduction to Higher Order Ambisonics

So, what is this Higher Order Ambisonics thing?

Well, it's quite a few things. Probably more than anything, it's a mathematical framework for handling 3D sound scenes or "soundfields". It uses a representation of the soundfield centred around a listener at the centre of the room.

3D Mixing FAQ

Here are some Frequently Asked Questions about the 3D mixing and the O3A plugins.

Binaural Audio and Head Tracking

Binaural stereo attempts to simulate 3D audio on headphones, by modifying sound as if it had travelled around your head and past your ears. However, on its own it often does not sound real, partly because it does not change when you turn your head.

Personalized HRTFs in Rapture3D Advanced

Rapture3D Advanced v2.7.0 introduces experimental support for the import of personalized HRTFs from AES69 files (if you are lucky enough to have such things).

Personalized HRTFs are effectively acoustic models of an individual's head. Using these, it is possible to create synthetic binaural stereo which is tailored for a particular individual.

Rapture3D Stereo Hints & Tips

If you're using Rapture3D in Stereo, there are quite a few things going on, some of which can be a bit confusing. Sorry. Hopefully this page will make some things a bit clearer!

Custom Layouts in Rapture3D Advanced

The main difference between the "User" and "Advanced" editions of Rapture3D is that the "Advanced" edition supports custom speaker layouts. It comes with a wider range of preset layouts than the "User" edition, which only supports the standard Windows layouts and a few variants.

Amber HRTF

"Amber" is a 3D HOA "binaural" decoder method for headphones that is available in Rapture3D and our pro audio products.

HOA Technical Notes - N3D/SN3D Reference Implementation

N3D and SN3D are representations of ambisonic B-Format with useful mathematical properties. They are common in the Higher Order Ambisonic literature and our plugins use SN3D.

HOA Technical Notes - SN3D B-Format

B-Format is the main audio format used for Higher Order Ambisonics. This is a multichannel audio format where the individual channels do not correspond directly to speaker feeds. There is no "front left" channel.

HOA Technical Notes - Decoding

In Higher Order Ambisonics, the main audio stream in use is B-Format. This contains an awful lot of information about sound directivity, and it is deliberately unaware of the speakers that you will use for playback. Because of this, it must be "decoded" for playback.