The Perception, Evaluation and Creative Application of High Order Ambisonics In Contemporary Music Practice
Natasha Barrett
Ircam Composer in Research Report 2012
In her residency at IRCAM Barrett investigated the technical and artistic implementation of Higher Order Ambisonic techniques. In this paper Barrett investigated a range of Higher Order Ambisonics in two dimensional and three dimensional spatializations noting differences in perception of 4th and 7th order 3D decoding suggesting the 7th order decoding is the most optimal working in 3D giving the most ‘transparent’ and precise results - while in 2D, 12th order decodings were only marginally advantageous in complex scenes, suggesting that 7th order decodings were also the optimal format. Barrett also investigated Near Field Compensated Higher Order Ambisonics discovering that higher order encoding/decoding can result in more convincing NFC results albeit with a necessity to compensate some of the addition of low frequency content with high pass filtering which may remove some of the NFC effect. Barrett also noted when working with NFC that the loudspeaker distances in the decoding stage require consideration at the encoding stage, at 12th order noting a variance range of 50-200% for accurate translation. Barrett was also able to use an Eigenmike to capture scenes at a high resolution 4th order sound field and compared this with older lower resolution Soundfield microphone technology (SPS200 and ST250) noting a greater ‘openness’ and spatial accuracy with the Eigenmike. Barrett goes on to discuss some of the other considerations in composing for Higher Order Ambisonics such as monitoring issues, accuracy in translation and the compositional advantages of working at this level. I enjoyed this window into the artistic and technical application of HOA, Barrett’s work is certainly beneficial for those working with higher order ambisonics.
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