Future Spatial Audio: Subjective Evaluation of 3D Surround Systems Paul James Power Acoustics Research Centre School of Computing, Science and Engineering College of Science and Technology University of Salford, Salford, UK Submitted in Partial Fulfilment of The Requirements of The Degree of Doctor of Philosophy Contents 1 Introduction ................................................................................................................................... 1 1.1 Perceptual Benefits of the Inclusion of Surround Channels ................................................... 1 1.1 Approach ................................................................................................................................. 2 1.2 Research Objectives ................................................................................................................ 3 1.3 Organisation of the Thesis ...................................................................................................... 4 1.4 Contributions to the Field ....................................................................................................... 6 2 Literature Review ......................................................................................................................... 8 2.1 History of Surround Systems .................................................................................................. 8 2.2 Surround With Height ............................................................................................................. 9 2.3 Spatial Rendering Methods in 3D Audio .............................................................................. 10 2.4 Perceptual Cues ..................................................................................................................... 11 2.5 Summary ............................................................................................................................... 16 2.6 Recording Localization Judgements ..................................................................................... 17 2.7 Summary ............................................................................................................................... 18 2.8 Localisation in Reproduced Sound ....................................................................................... 18 2.9 Summary ............................................................................................................................... 22 2.10 Number of Channels and Positioning in 3D Surround Systems and its Impact on Envelopment ..................................................................................................................................... 23 2.11 Spatial Audio Quality in 3D Surround .................................................................................. 25 2.12 Summary ............................................................................................................................... 31 2.13 Initial Area for Investigation ................................................................................................. 32 3 Surround Sound Development ................................................................................................... 33 3.1 Introduction ........................................................................................................................... 33 3.2 Development of Spatial Audio Systems ............................................................................... 33 3.2.1 Mono ............................................................................................................................. 33 3.2.2 Binaural ......................................................................................................................... 33 3.2.3 Stereo ............................................................................................................................ 34 3.2.4 Quadraphonics .............................................................................................................. 36 3.2.5 5.1 Surround .................................................................................................................. 37 ii 3.2.6 Summary ....................................................................................................................... 39 3.3 Surround With Height ........................................................................................................... 39 3.3.1 NHK 22.2 ...................................................................................................................... 39 3.3.2 Dolby Pro Logic IIz ...................................................................................................... 40 3.3.3 10.2 ................................................................................................................................ 41 3.3.4 Dolby Atmos ................................................................................................................. 43 3.3.5 Summary ....................................................................................................................... 43 3.4 Spatializing Methods for 3D Reproduction .......................................................................... 44 3.4.1 Vector Base Amplitude Panning ................................................................................... 44 3.5 Ambisonic Encoding/Decoding ............................................................................................ 46 3.5.1 Introduction ................................................................................................................... 46 3.5.2 Ambisonic Encoding ..................................................................................................... 47 3.5.3 SoundField Microphone ................................................................................................ 47 3.5.4 Eigenmike ..................................................................................................................... 48 3.5.5 Theoretical Encoding .................................................................................................... 49 3.5.6 Resolution of Different Ambisonic Orders ................................................................... 51 3.5.7 Decoder Types .............................................................................................................. 53 3.5.8 Dual Band Decoder ....................................................................................................... 55 3.5.9 Limits to Correct Soundfield Reconstruction ............................................................... 56 3.5.10 Near Field Compensation .............................................................................................. 56 3.5.11 Speaker Array Configuration ........................................................................................ 56 3.5.12 Platonic Solids .............................................................................................................. 57 3.5.13 Irregular Layouts ........................................................................................................... 58 3.5.14 With Height Irregular Layout Solutions ....................................................................... 58 3.6 Normalisation Schemes......................................................................................................... 58 3.6.1 FurseMalham (FuMa) ................................................................................................... 59 3.6.2 N3D ............................................................................................................................... 59 3.6.3 SN3D ............................................................................................................................. 59 3.7 Summary ............................................................................................................................... 60 iii 3.8 Human Hearing Mechanisms in Spatial Audio ..................................................................... 61 3.8.1 Median Plane ................................................................................................................ 62 3.8.2 Frontal Plane ................................................................................................................. 63 3.8.3 Cone of Confusion ........................................................................................................ 64 3.8.4 Precedence Effect .......................................................................................................... 64 3.8.5 Masking ......................................................................................................................... 65 3.8.6 Summary ....................................................................................................................... 67 3.9 Assessment of Spatial Audio Quality ................................................................................... 67 3.9.1 Spatial Impression in Concert Hall Acoustics .............................................................. 71 3.10 Purpose of Spatial Audio Systems ........................................................................................ 71 3.10.1 Objective Measures ....................................................................................................... 72 3.10.2 Importance of the Direction of Reflections in Concert Hall Acoustics in Terms