Ambisonics is a system of recording and playback of soundfields. A soundfield is just a word for describing sounds in the environment around us, and usually implies 3 dimensions. This two-part system of recording and playback is built upon strong mathematical foundations and theories of human hearing. For recording in Ambisonics, an array of microphone capsules are built into one microphone called a Soundfield microphone. Soundfield mike recording are then processed and encoded into a special format, called B-format, which may be written onto and distributed through many different media. Finally, a decoder is used to process and recover the soundfield and play it back in any number of listening setups (from simple stereo, to "5.1 Surround Sound", to any number of speakers located at known locations within a room), with a unique output for every speaker available.

Sounds come to us in the form of waves of pressure in the air, much like images come to us in the form of waves of intensity of light. Anything that produces light or sound is called a "source." So, a light bulb is a source of light, and a person's voice is a source of sound. And just like light, sounds are reflected off of all the surfaces around you. It is because of all this "bouncing around" that you can see and hear things in the environment. Contained within this bouncing of waves is information about what the sources are, and where they are located--perhaps a blue light bulb in the middle of the ceiling, or a crow cawing from the telephone line above.

It is easy to recognize that light is coming from all directions--you can just look around and see every object and surface in your environment. For sound, this is not as easy. While you can look at a spot on the floor and see that it is brown, for instance, it is much harder to hear the sound coming from that same location. There is, in fact, sound coming to you from that brown spot, as with all surfaces in your environment, but it is difficult characterize. This is because the human brain performs a lot of processing on the sounds that reach your ears before you are even able to think about them. It is often obvious what is making a particular sound and where it is coming from (like the hum of refigerator in the next room), even though it cannot be directly seen. This is the brain at work. People simply turn their head to point in the direction of the source of a sound.

There are several ways in which the brain processes soundfield information. Much of the processing relies on differences between sounds that reach the ears. For instance, if a sound is played to your right, because your right ear is closer, it receives the sound first. This is called Interaural Time Delay (ITD). Also, the sound is quieter in the left ear, not only because it is farther away, but because your head absorbs some of the sound. This is called Interaural Level Difference (ILD). The brain also pays attention to the timing between and relative loudness of sounds coming directly from the source and sounds reflected off of walls and other surfaces. Sources that are farther away tend to have more reflected energy than direct energy reaching the ears. These ear-brain interactions are called "psychoacoustics."

In making a soundfield recording as much information about a very small volume of space is gathered and recorded. That information is comprised of simply measurements of air pressure and air pressure changes. Building upon recording techniques for stereo developed by Alan Blumlein in the 1930s, Ambisonics extends the recording of information into the third dimension. The idea is to record not only the pressure at a location, but also the pressure changes in different directions (front-back, left-right, and up-down). With proper decoding of this information using mathematics as well as psychoacoustics, a soundfield is produced by speakers in the room that reconstructs what was going on in that small volume at the listener's location.