Is My Decoder Ambisonic? Aaron J. Heller Artificial Intelligence Center, SRI International Menlo Park, CA 94025, USA Email:
[email protected] Richard Lee Eric M. Benjamin Pandit Littoral Dolby Laboratories Cooktown, Queensland 4895, AU San Francisco, CA 94044, USA Email:
[email protected] Email:
[email protected] Revision 2 Abstract In earlier papers, the present authors established the importance of various aspects of Am- bisonic decoder design: a decoding matrix matched to the geometry of the loudspeaker array in use, phase-matched shelf filters, and near-field compensation [1, 2]. These are needed for accurate reproduction of spatial localization cues, such as interaural time difference (ITD), interaural level difference (ILD), and distance cues. Unfortunately, many listening tests of Ambisonic reproduction reported in the literature either omit the details of the decoding used or utilize suboptimal decoding. In this paper we review the acoustic and psychoacoustic criteria for Ambisonic reproduc- tion, present a methodology and tools for “black box” testing to verify the performance of a candidate decoder, and present and discuss the results of this testing on some widely used decoders. Keywords: Ambisonics, decoder design, listening tests, surround sound, psychoacoustics NOTE: This is a revised and corrected version of the paper presented at the 125th Convention of the Audio Engineering Society, held October 1 – 5, 2008 in San Francisco, CA USA $Id: imda-revised.tex 25737 2012-06-10 23:40:07Z heller $ 1 1 INTRODUCTION rience with good Ambisonic reproduction, we This paper is about testing Ambisonic de- might have stopped there and written off Am- coders.