Ambisonic replay systems

Ambisonic Playback Systems.

There are many potential variations of playback systems suitable for the replay of Ambisonic recordings. They can range from as little as four to as many speakers that a room could physically accommodate. The speakers can be arranged in a variety of ways, to either suit the layout of a space or a users preference. The distinct advantage that Ambisonic playback systems have over conventional set ups is that rather than relying on multiple phantom images being created between loudspeakers to create the surround experience, these systems use the loudspeaker as a means to generate wavefronts similar to those generated by the sound source at the recording stage. Put simply the loudspeakers work together to create a wavefront rather than a single multi-channel stem driving a single loudspeaker.

This means that if the number of loudspeakers, and their position is known, then the B-format sound files can employ the loudspeakers to re-create the wavefronts captured at the time of the recording by means of a suitable decoder.

The system that I will be using to replay the B-Format recordings made for this project is located in the Digital Design Studio in Glasgow. The Digital Design Studio is part of the Glasgow School of Art and is located in 'The Hub' near Pacific Quay. The Digital Design Studio system comprises 12 loudspeakers arranged in a format similar to the one seen here in this BBC video demonstrating their research into Ambisonics.




The speakers are arranged in groups of four: four to give planar information and a further 8 to provide the periphonic or height information (4 above and 4 below the X and Y axis)

When testing the recordings through this system I was amazed at how well it provided a really cohesive sounding environment. What this means is that I was unable to pinpoint the location of any one loudspeaker in respect of a sound emitting from it. The periphonic information that I had hoped to capture was most definitely present as I was able to easily locate sound sources accurately in all directions. Having tested out both the video and audio replay system I was confident that the listening tests would provide favourable results that would most certainly support the arguments outlined in my Dissertation and Reseach module.

Commercial Success?

If Ambisonic replay systems are ever to be employed outside of specialist facilities or the listening environments of enthusiasts, then the ITU, manufacturers of DSP software, manufacturers of replay equipment and such like must begin to develop or agree upon a set of standards which allows this exiting prospect the opportunity to develop further. Until this happens I suspect that this technology will remain dormant for several years to come. Can we draw parallels with the Nyquist Theorem in the 30's and its eventual adoption in the field of digital audio fifty years later? I hope not, otherwise we will have some years to wait before Ambisonics becomes common place. That is of course unless academics and practitioners keep making the arguments in favour of this technology, bringing it to the attention of the masses and manufacturers alike.