SOUNDFIELD ANALYSIS and SYNTHESIS: Recording, Reproduction and Compression by SHUAI WANG Athesis presented to the University of New South Wales in fulfilment of the thesis requirement for the degree of Master of Engineering (Research) in Electrical Engineering Kensington, Sydney, Australia c Shuai Wang, 2007 Originality Statement I hereby declare that this submission is my own work and to the best of my knowl- edge it contains no material previously published or written by another person, or substantial proportions of material which have been accepted for the award of any otherdegreeordiplomaatUNSWoranyother educational institution, except where due acknowledgement is made in the thesis. Any contribution made to the research by others, with whom I have worked at UNSW or elsewhere, is explicitly acknowledged in the thesis. I also declare that the intellectual content of this thesis is the product of my own work, except to the extent that assistance from others in the project’s design and conception or in style, presentation and linguistic expression is acknowledged. I further authorize the University of NSW to reproduce this thesis by photocopying or by other means, in total or in part, at the request of other institutions or individuals for the purpose of scholarly research. ii Acknowledgments As the author of this dissertation, I would like to express my deep and sincere gratitude to my supervisor, Dr. D. Sen, for his inspiration and guidance throughout all the work of this research. It has been a great pleasure to conduct my research under his supervision, and his extraordinary patience and encouragement have helped me conquer various kinds of problems along the way. Many thanks are also granted to other members from both our research group and school of Electrical Engineering and Telecommunications at the University of New South Wales for their kind help in various forms. Last but not least, I wish to ascribe this thesis to my family for their consistent support and love. iii Publications • S. Wang, D. Sen, W. Lu, “Subband Analysis of Time Delay Estimation in STFT Domain,” Proc. Eleventh Australian International Conference on Speech Science and Technology, pp.211-215, 2006. iv Abstract Globally, the ever increasing consumer interest in multichannel audio is a major factor driving the research intent in soundfield reconstruction and compression. The popularity of the well commercialized 5.1 surround sound system and its 6-Channel audio has been strongly supported by the advent of powerful storage medium, DVD, as well as the use of efficient telecommunication techniques. However, this popularity has also revealed potential problems in the development of soundfield systems. Firstly, currently available soundfield systems have rather poor compatibility with irregular speaker arrangements. Secondly, bandwidth requirement is dramatically in- creased for multichannel audio representation with good temporal and spatial fidelity. This master’s thesis addresses these two major issues in soundfield systems. It introduces a new approach to analyze and sysnthesize soundfield, and compares this approach with currently popular systems. To facilitate this comparison, the behavior of soundfield has been reviewed from both physical and psychoacoustic perspectives, along with an extensive study of past and present soundfield systems and multichannel audio compression algorithms. The 1th order High Spatial Resolution (HSR) soundfield recording and reproduction has been implemented in this project, and subjectively evaluated using a series of MUSHRA tests to finalize the comparison. v Contents 1 Introduction 1 1.1BackgroundOverview........................... 1 1.2ReconstructionSystems.......................... 4 1.3MotivationforCurrentProject...................... 6 1.4Contribution................................. 8 1.5DissertationOverview........................... 10 2 Soundfield Physics and Psychoacoustics 12 2.1PhysicalRepresentation.......................... 13 2.2Psychoacoustics............................... 17 2.2.1 Spatialhearingwithonesoundsource.............. 17 2.2.2 SpatialHearingwithTwoSoundSources............. 21 2.3Summary.................................. 24 3 Soundfield Systems and Multichannel Audio Compression Techniques 25 3.1 Historic Review of Soundfield Reconstruction Systems . ....... 25 3.1.1 3-ChannelSystem.......................... 26 3.1.2 Stereophony............................. 29 vi 3.1.3 Quadraphony............................ 33 3.1.4 Ambisonics............................. 34 3.1.5 WaveFieldSynthesis(WFS).................... 37 3.1.6 Ambiophonics and Vector Based Amplitude Panning (VBAP) . 39 3.1.7 Summary.............................. 40 3.2SummaryofMultichannelAudioCompressionTechniques....... 41 3.2.1 LosslessAudioCoding....................... 41 3.2.2 LossyAudioCoding........................ 42 3.3Summary.................................. 48 4 Multichannel Audio Compression Technique: Binaural Cue Coding (BCC) 49 4.1ProblemReview............................... 49 4.2BCCDesignScheme............................ 51 4.2.1 MacroscopicDesign......................... 52 4.2.2 FrequencyProcessing........................ 53 4.2.3 Encoding.............................. 56 4.2.4 Decoding.............................. 65 4.3Summary.................................. 66 5 High Spatial Resolution(HSR) Soundfield System 69 5.1ReviewofMicrophones........................... 70 5.2HighSpatialResolution(HSR)Recording................. 77 5.3Reproduction................................ 79 5.4Post-recordingProcessing......................... 80 vii 5.4.1 Analysis............................... 81 5.4.2 Synthesis.............................. 84 5.5Summary.................................. 88 6 Experiments and Results 90 6.1ExperimentsonBCCImplementation................... 90 6.1.1 EstimationofICTD........................ 91 6.1.2 Pre-echoingEffect.......................... 96 6.2AcousticExperimentsPreparation..................... 98 6.2.1 Anechoicchamber.......................... 99 6.2.2 SpeakerArrayConfiguration....................100 6.2.3 MicrophoneArrayConfiguration.................103 6.2.4 SubjectiveTests...........................105 6.3MUSHRATestsandResults........................107 6.3.1 MUSHRATestsonBCC......................108 6.3.2 MUSHRA Tests on HSR Soundfield Systems ...........110 7 Conclusion 118 7.1SummaryofThisProject..........................118 7.2FutureWorks................................119 Appendices A Spherical Solutions to the Wave Equation 121 A.1 Solving the Wave Equation in Spherical Coordinates . ......121 A.2 Spherical Bessel Functions of the 1st Kind ................122 A.2.1Plot.................................122 A.2.2Properties..............................123 viii B Information about Speaker and Wedge 124 B.1 GENELEC Loudspeakers (8130A)....................124 B.2Wedge‘A’..................................125 C Stimuli of MUSHRA Tests on Soundfield Systems 127 C.1 Matrix F and Parameter μ .........................127 C.2VariationsinStimuli............................128 ix List of Figures 1.1GeneralStructureofSoundReconstructionSystems........... 4 1.2DifferentSoundReconstructionSystems................. 4 2.1AChirpSignalRecordedbyanOmnidirectionalMicrophone...... 13 2.2 Spherical Coordinates ............................ 14 2.3SpatialHearingwithOneSoundSource.................. 18 2.4BinauralSignals............................... 19 2.5TheHeadShadowingEffect........................ 20 2.6SummingLocalization........................... 22 2.7SuperpositionofMultipleAuditoryEvents................ 23 3.1TheHuygens’Principle........................... 27 3.2SteinbergandSnow’s3-ChannelSystem................. 28 3.3StereophonicRecordingandReproduction................ 30 3.4QuadraphonicSetup............................ 34 3.5 Soundfield Microphone.......................... 35 3.6B-formatDirectionality........................... 36 3.7 ITU-R BS.775, 5.1 Surround Sound Speakers Placement . ..... 37 3.8ThePrincipleofWaveFieldSynthesis.................. 38 3.9AmbiophonicsReproduction........................ 39 3.10GenericStructureofLossyAudioCoding................. 43 4.1GenericStructureofBinauralCueCoding(BCC)............ 52 x 4.2MacroscopicStructuresofBCCAnalysisandSynthesis......... 52 4.3OverlappedHannWindows........................ 55 4.4FineStructureofBCCEncoder...................... 57 4.5UniformQuantizationScheme....................... 64 4.6FineStructureofBCCDecoder...................... 65 5.1 Generic Structure of Soundfield Systems ................. 70 5.2StandardMicrophones’2DPolarPattern................. 71 5.3TheDecompositionofB-formatDirectionality.............. 73 5.4DoubleM/SMicrophoneDesignScheme................. 74 5.5ORTFStereoRecordingMicrophone................... 75 5.6 The Configuration of Decca Tree Microphone ............... 76 5.7Post-RecordingAnalysisSystem...................... 82 5.8Post-recordingAnalysis........................... 83 5.9Post-recordingSynthesis.......................... 84 5.10 High Spatial Resolution Soundfield System ................ 88 6.1TDEforMulti-Sinusoids:IntegerSamples................ 93 6.2TDEforMulti-Sinusoids:Non-integerSamples.............. 94 6.3TDEforMulti-Sinusoids:Complex.................... 95 6.4Pre-echoingEffects............................. 97 6.5AdaptiveWindowingScheme....................... 98 6.63DGeometricModeloftheAnechoicChamber..............100 6.7GeometricSimulationofSpeakerMounting................101 6.8 Vogels Loudspeaker Support .......................101