Localisation of Elevated Sources in Higher-Order Ambisonics

Increasing the order of ambisonic reproduction allows 3D sound fields to be reconstructed with improved resolution and enhanced localisation, at the expense of higher channel counts, increased broadcast bandwidth, and increased storage requirements. Due to the resolution of human hearing it is possible that lowerorder reproduction is sufficient for elevated sources in comparison to sources located in the horizontal plane, and so for 3D reproduction mixed-order ambisonic renderings may be the most efficient use of available transmission bandwidth and storage capacity. We report the results of subjective localisation tests for virtual sources placed in the vertical plane at various elevations and azimuths, for first, second and third-order ambisonic reproduction over a 16-loudspeaker system. The results provide insights into the requirements of higher-order ambisonics for broadcast and domestic reproduction. The material in this paper was originally presented at the Institute of Acoustics Reproduced Sound conference in November 2012: P. Power, W. J. Davies, J. Hirst and C. Dunn, "Localisation of Elevated Virtual Sources in Higher-Order Ambisonic Soundfields," IOA conference Reproduced Sound 28, Brighton, UK (2012). Additional key words: 3D sound, ambisonics, height, HOA, localisation, mixed order, surround sound