The order of an Ambisonic recording or audio file relates to the precision with which sound sources in the recording can be localised. The higher the order, the more accurately the sound source can be pinpointed by the listener.
It also relates directly to the realism of the recording – how close it sounds to the real world experience. This is because the localisation of the reflections, the sound source creates in the environment, also increases with higher orders. Orders above 1 are called Higher Order Ambisonics (HOA).
And it influences the number of channels used by the audio file:
- 1st order: 4 channels
- 2nd order: 9 channels
- 3rd order: 16 channels
- 4th order: 25 channels
- etc. (number of channels = (order – 1)^2)
Munk Productions Ambisonic Ambiences are recorded and produced in 3rd order Ambisonics. This makes our ambiences some of the most realistic ambience recordings available.
To illustrate the precision of 3rd order vs 1st order (which is normally found in Ambisonic ambience libraries), look at these images:
Listening tests have shown 3rd order to be a good trade-off between number of channels and perceived localisation accuracy.
In the real world, our brains are used to processing sound with a very high precision, both from the sound sources themselves, but also from the many reflections generated when sound waves hit various surfaces, particularly below sound sources, before entering the ears. Not only do these reflections help the brain to localise the source, they are also part of listening to sound in the real world. So for a recording to sound “real”, it must include these reflections with a reasonably high degree of accuracy. Our ambiences do.
Listen for yourself on the front page of the Munk Productions Shop.
Information on these pages about MPAA is presented in a decidedly non-scientific fashion. It is meant as an easy to understand introduction to certain Ambisonic aspects, and to our ambiences in particular.
If you’re interested in a more scientific description of listening tests, reflections and Ambisonics, see the Further Reading page for suggestions.