Ambisonics and Periphony

The word Ambisonic takes its name from the Latin words ambien, meaning “going around” and sonus, meaning “sound”. It means, quite literally, “encompassing sound” and is used to describe one technology that we are investigating to reproduce truly three-dimensional sound.

The way that Ambisonics works differs from that of other surround sound formats, such as 5.1. Rather than storing sound for a specific speaker layout, Ambisonics captures the entire 3D sound field as a set of spherical harmonics which can then be decoded for a wide variety of speaker layouts, including stereo and 5.1. This, of course, allows the audience to choose the layout that best suits their listening environment.

Although the principles of Ambisonics were developed in the 1970s, the costs involved in producing such a system made it impractical at that time. However, recent developments and the increased availability of affordable computing power means that it has at last become a viable solution.

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Ambisonics is equally as comfortable with conventional 2D surround sound – which can be ‘upmixed’ from 5.1 – as it is with 3D surround sound, which includes the extra dimension of height. The format is also scalable, so it can make the best possible use of any future increases in bandwidth.

Periphony is the term used to describe the use of the vertical dimension in sound reproduction – the addition of a height component to conventional stereo or surround sound. Placing loudspeakers above and below the listener’s head height can allow a much more realistic portrayal of, for example, ambience within enclosed spaces or atmospheric effects outdoors. Ambisonics provides a way of using the vertical component, although it is not the only way.

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Discover more about the science behind Ambisonics and learn how to make your very own Click ambisonic microphone.

As part of the project we hope to evaluate the various costs and benefits of Ambisonics and periphony, both to the broadcaster and the
audience. At present we are examining new production methods to create high-quality Ambisonics content while at the same time looking at how to integrate it into the broadcast chain and provide the best possible experience for a variety of listening environments.

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