Applications in Heart Rate Variability
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Data Analysis through Auditory Display: Applications in Heart Rate Variability Mark Ballora Faculty of Music McGill University, Montréal May, 2000 A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements of the degree of Doctor of Philosophy in Music © Mark Ballora, May 2000 Table of Contents Abstract......................................................................................... v Résumé ........................................................................................ vi Acknowledgements ..........................................................................vii 1. Introduction 1.1 Purpose of Study.................................................................... 1 1.2 Auditory Display.................................................................... 2 1.3 Types of Auditory Display ........................................................ 3 1.4 Heart Rate Variability.............................................................. 4 1.5 Design of the Thesis................................................................ 6 2. Survey of Related Literature 2.1 Data in Music 2.1.1 Data Music—Making Art from Information............................ 8 2.1.2 Biofeedback Music........................................................14 2.1.3 Nonlinear Dynamics in Music ...........................................16 2.1.3.1 Fractal Music...................................................16 2.1.3.2 Mapping Chaotic (and other) Data ..........................18 2.1.4 Concluding Thoughts on Data as Music................................23 2.2 Auditory Display...................................................................25 2.2.1 Elements of Auditory and Visual Displays ............................25 2.2.2 Background Work in Auditory Display ................................27 2.2.3 Monitoring Implementations.............................................29 2.2.4 Analysis Implementations................................................30 2.2.4.1 Rings of Saturn.................................................31 2.2.4.2 Seismology .....................................................31 2.2.4.3 Financial Analysis.............................................33 2.2.4.4 Quantum Mechanics ..........................................34 2.2.4.5 Fluid Dynamics ................................................34 2.3 Heart Rate Variability.............................................................35 2.3.1 Spectral Analyses..........................................................36 2.3.2 Statistical Analyses........................................................37 2.3.3 Nonlinear Dynamics 2.3.3.1 Nonlinear dynamics and biological systems ...............37 2.3.3.2 Magnitude fluctuation analysis ..............................39 2.3.3.3 Spectrum of first-difference series ..........................41 2.3.3.4 Detrended fluctuation analysis...............................44 2.3.3.5 Cumulative variation amplitude analysis (CVAA)........44 3. Choice of Software 3.1 Software Synthesis.................................................................57 3.2 Method of Illustration: Unit Generators and Signal Flow Charts...........58 3.3 Software Synthesis and Real Time Systems ...................................59 3.4 Operational Features of SuperCollider 3.4.1 A virtual machine that runs at interrupt level..........................60 3.4.2 Dynamic typing............................................................62 3.4.3 Real time garbage collection.............................................62 3.4.4 Object oriented paradigm.................................................65 3.5 SuperCollider Syntax..............................................................68 3.6 Other Features of SuperCollider 3.6.1 Graphical User Interface..................................................69 ii 3.6.2 Ease of Use .................................................................70 3.6.3 Spawning Events ..........................................................70 3.6.4 Collection Classes .........................................................70 3.6.4 Sample Accurate Scheduling of Events ................................71 3.7 Another Example: Can the Ear Detect Randomized Phases? ...............71 4. Description of HRV Sonification 4.1 Development of a Heart Rate Variability Sonification Model...............74 4.1.1 Heart Rhythms in Csound 4.1.1.1 Description of Csound model................................74 4.1.1.2 Flowchart Illustration .........................................77 4.1.1.3 Evaluation of Csound model.................................77 4.1.2 Unit Generators Used in SuperCollider Sonification .................80 4.1.2.1 PSinGrain.......................................................80 4.1.2.2 Phase Modulator...............................................80 4.1.3.3 Wavetable.......................................................81 4.1.3.4 Band Limited Impulse Oscillator............................82 4.1.3.5 Klang ............................................................82 4.1.3.6 Envelope Generator ...........................................82 4.1.3 SuperCollider Sonification 1: Cumulative Variation Amplitude Analysis 4.1.3.1 Components of the CVAA Sonification....................83 4.1.3.1.1 Beat to Beat........................................85 4.1.3.1.2 NN/Median Filt ...................................85 4.1.3.1.3 NN50 ...............................................86 4.1.3.1.4 Wavelet.............................................86 4.1.3.1.5 Hilbert Transform.................................86 4.1.3.1.6 Median Filtered ...................................87 4.1.3.1.7 Timbres.............................................87 4.1.3.1.8 Median Running Window .......................87 4.1.3.2 Flowchart Illustration, Code and Demonstrations.........89 4.1.3.3 Evaluation of CVAA Sonification...........................89 4.1.4 SuperCollider Sonification 2: A General Model 4.1.4.1 Components of the Sonification .............................90 4.1.4.1.1 Discrete Events 4.1.4.1.1.1 NN Intervals ........................91 4.1.4.1.1.2 NN50 Intervals .....................91 4.1.4.1.2 Continuous Events................................91 4.1.4.1.2.1 Mean Value .........................92 4.1.4.1.2.2 Standard Deviation Value.........92 4.1.4.2 Flowchart Illustration, Code and Demonstrations.........92 4.1.4.3 Evaluation of General Model ................................94 4.2 Listening Perception Test 4.2.1 Purpose of the Test ........................................................96 4.2.2 Method ......................................................................97 4.2.3 Results.......................................................................98 4.2.4 Other Descriptive Statistics ............................................ 102 4.2.5 Results for Each Diagnosis............................................. 105 4.2.6 Discussion ................................................................ 109 4.3 SuperCollider Sonification 3: Diagnosis of Sleep Apnea 4.3.1 Modifications to General Model....................................... 111 4.3.2 Flowchart Illustration, Code, and Demonstration ................... 116 iii 5. Summary and Conclusions 5.1 Method of Sonification.......................................................... 119 5.2 Auditory Display in Cardiology ............................................... 121 5.3 Future Work ...................................................................... 121 5.4 General Guidelines for the Creation of Auditory Displays ................ 122 5.5 Concluding Thoughts............................................................ 123 Appendices 1. Fundamental Auditory Concepts and Terms 1. Sound and Time .............................................................. 125 2. Pitch............................................................................ 126 3. Timbre ......................................................................... 129 4. Volume ........................................................................ 133 5. Localization................................................................... 136 6. Phase........................................................................... 138 2. Nonlinear Dynamics 1. Iterative Functions, Asymptotic States and Chaos....................... 141 2. Fractals ........................................................................ 145 3. Scaled Noise .................................................................. 148 3. Description of the Poisson Distribution............................................. 151 4. Csound Code for Encoding Instrument Orchestra File............................ 153 5. SuperCollider code for HRV Sonification Models 1. CVAA Sonification ............................................................... 157 2. General Model ..................................................................... 160 3. Apnea Diagnosis Model .......................................................... 162 6. Listening Perception Test Materials 1. Training Session for Listening Perception Test ............................... 166 2. Listening Perception Test Response Forms.................................... 169 3. Listening Perception Test Visual Displays..................................... 171 References ..................................................................................... 195 Accompanying CD Audio: Track 1: Csound Sonification of Healthy Subject Tracks 2-29: Sound Files used for Listening Perception