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Som 3 Handout.Pdf Sound of Music How It Works Session 3 Hearing Music and the Ear OLLI at Illinois Spring 2020 Endlessly Downward Beatsystem D. H. Tracy emt 5595 (1995) Sound of Music How It Works Session 3 Hearing Music and the Ear OLLI at Illinois Spring 2020 D. H. Tracy Course Outline 1. Building Blocks: Some basic concepts 2. Resonance: Building Musical Sounds 3. Hearing Music and the Ear 4. Musical Scales 5. Musical Instruments 6. Singing and Musical Notation 7. Harmony and Dissonance; Chords 8. Combining the Elements of Music 2/11/2020 Sound of Music 3 4 OLLI-Vote 2020 Wands NO MAYBE BAD YES ??? GOOD 2/11/2020 Sound of Music 3 5 2/11/2020 Sound of Music 3 6 Human Ear 2/11/2020 Sound of Music 3 7 The Middle Ear Blausen 2/11/2020 Sound of Music 3 8 The Inner Ear 2/11/2020 Sound of Music 3 9 Auditory Transduction: Sound to Electrical Impulses Cochlea Ear Video Brandon Pletsch (2002) Medical College of Georgia 2/11/2020 Sound of Music 3 10 Detailed Look at the Cochlea Basilar Membrane Jennifer Kincaid 2/11/2020 Sound of Music 3 11 Another Cartoonish look at ear…. Ear “Journey of Sound to the Brain” Video NIH - 2017 [Wikimedia|Cochlea] Stereocilia 2/11/2020 Sound of Music 3 12 Detailed Look at the Organ of Corti Ear Video Outer Hair Cells Inner Hair Cells 2/11/2020 Sound of Music 3 Jennifer Kincaid 13 Detailed Look at the Organ of Corti Waves Coming Towards Us 3500 Inner Hair Cells Supercilia Outer Hair Cell (Amplifier) Inner Hair Cell (Sensing) 2/11/2020 Sound of Music 3 Jennifer Kincaid 14 Detailed Look at the Organ of Corti Outer Hair Cell (Amplifier) Inner Hair Cell (Sensing) Nerve Fibers to Brain 2/11/2020 Sound of Music 3 Jennifer Kincaid 15 Tectorial Membrane Peeled Back Electron Micrographs of Guinea Pig Organ of Corti [Prof. Andrew Forge] 2/11/2020 Sound of Music 3 16 Severe Damage 2/11/2020 Sound of Music 3 17 Outer Hair Cells Shake the Tectorial Membrane Inner Hair Cell Supercilliae almost (but not quite) touching the Tectorial Membrane. Outer Hair Cells (attached to Membrane) Inner Hair Cells 2/11/2020 Sound of Music 3 18 Dancing Outer Hair Cell with Stereocilia Isolated Guinea Pig Outer Hair Cell with Patch Clamp J. Santos-Sacchi Yale University 2/11/2020 Sound of Music 3 19 Unrolling the Cochlea Response at one 2/11/2020 Sound of Music 3 middle frequency 20 Unrolling the Cochlea Animated Video of Basilar Membrane 0.1 mm 35 mm High f 10,000 x Stiffer! 0.5 mm Basilar Membrane Low f Howard Hughes Medical Institute Sound of Music 3 2/11/2020 21 Traveling Wave on Basilar Membrane Traveling wave moves slowly – ~1% of speed of sound in air Relative Amplitudes 1600 Hz 800 Hz 400 Hz 200 Hz 100 Hz 50 Hz 25 Hz Distance from Stapes (mm) But these Basilar Membrane responses were measured on “dead” Cochleas… 2/11/2020 Sound of Music 3 22 Traveling Wave on Basilar Membrane Relative Amplitudes 1600 Hz 800 Hz 400 Hz 200 Hz 100 Hz 50 Hz 25 Hz Distance from Stapes (mm) 2/11/2020 Sound of Music 3 23 Dancing Outer Hair Cells to the Rescue 400 Hz Basilar Membrane Response Relative Amplitudes 1600 Hz With Outer 800 Hz Hair Cell 400 Hz Amplification 200 Hz 100 Hz 50 Hz 25 Hz Outer Hair Cell Activation gives Inert Cochlea stronger and sharper signalDistance for from Inner Hair Cell sensors: Stapes (mm) Positive Feedback 0 10 20 30 Distance from Stapes (mm) 2/11/2020 Sound of Music 3 24 Dancing Outer Hair Cells to the Rescue High f Basilar Membrane Response Low f Relative Amplitudes 1600 Hz With Outer 800 Hz Hair Cell 400 Hz Amplification 200 Hz Critical Bands 100 Hz ▪ 25 bands across audible spectrum 50 Hz ▪ 1.3 mm wide along Basilar Membrane ▪ 150 Inner Hair Cells within a band 25 Hz ▪ Each Inner Hair Cell belongs to a Critical Band Inert Cochlea ▪ Frequency range of bands varies:Distance from o 100 Hz at low frequenciesStapes (mm) o 3000 Hz at high end 0 10 20 30 Distance from Stapes (mm) ▪ Important for understanding Harmony 2/11/2020 Sound of Music 3 25 Spontaneous OtoAcoustic Emission (SOAE) • 24/7 • Frequencies are individual, per ear • At least 70% of people have SOE! • Can be loud enough to hear (rarely!) ③ ② ① 2000 de Kleine et al JASA (2000) 2/11/2020 Sound of Music 3 26 SOAE is Similar to PA System Squeal… 2/11/2020 Sound of Music 3 27 Transient Evoked OtoAcoustic Emission (TEOAE) • “Click” Stimulus evokes delayed emission • Works on everyone • Routine baby screen for ear function • Very High signal – no need for quiet booth 2/11/2020 Sound of Music 3 28 Hermann Helmholtz had it mostly right Place Theory: Frequency perception is determined by distance along the Basilar Membrane 2/11/2020 Sound of Music 3 29 Hair Cells Fire Near Sound Wave Peak For Low frequencies (50-300 Hz): 2/11/2020 30 Sound of Music 3 Hair Cells Fire Near Sound Wave Peak For Medium Frequencies (500-5000 Hz): Volley Theory: (Ernest Wever 1939) Multiple nearby hair cells taken together can send a spike on every cycle 2/11/2020 Sound of Music 3 31 The Decibel Scale of Sound Pressure Level D=2m Units are Decibels (dB) 200 180 D=5m Each 20 dB → 10x Pressure 160 Each 10 dB → 10x Power SPL 140 Each 10 dB → ~2x “Loudness” (dB) 120 → D=50m Each 1 dB Min Change (JND) 100 Just Noticeable Difference 80 70 60 D=2m 40 D=2m 20 D=2m 0 Min -20 2/11/2020 Sound of Music 3 32 Equal Loudness Contours (ISO 226:2003) Units of Subjective Loudness are Phons [Phons = dB @ 1kHz] Old Data For 20-year olds! (1937) We’re 15-30dB worse off Frequency (Hz) 2/11/2020 Sound of Music 3 33 Hearing Threshold Drops with Age 2/11/2020 Sound of Music 3 34 (Edited) A Day in The Life… 1967 0 5000 10000 15000 20000 Hz 2/11/2020 Sound of Music 3 35 (Edited) A Day in The Life… 1967 0 5000 10000 15000 20000 Hz 2/11/2020 Sound of Music 3 36 Two Approaches to Understanding Musical Sound Perception 1. Follow the neurons from the ears onward - Bottom up 2. Look at the final perceptions of sound - Top down 2/11/2020 Sound of Music 3 37 Simplified Auditory Pathways 6. Auditory Cortex 5 4 1. Cochlea Sinauer Associates 3 2016 2 2/11/2020 Sound of Music 3 38 Simplified Auditory Pathways 6. Auditory Cortex 5. Medial Geniculate Body 4. Inferior Colliculus 1. Cochlea Sinauer Associates 3. Superior 2016 Olivary 2. Cochlear Complex Nucleus 2/11/2020 Sound of Music 3 39 to Left Medial to Right Medial Most Auditory Geniculate Body & Geniculate Body Auditory Cortex Brain Regions Inferior Colliculus are Tonotopic (at least partially) Lateral Lemniscus Cochlear Nucleus Cochlea Superior Olivary Complex 2/11/2020 Sound of Music 3 40 Including Auditory Cortex In Humans fMRI: High Resolution Functional MRI on Human Subjects: While hearing tones of various frequencies! Kamil Ugurbil et al (2015-2016) 2/11/2020 Sound of Music 3 41 “Typical” Neuron Dendrites (inputs) Nerve Impulse Cell Body Axon Axon Terminals (outputs) Myelin Protective Sheaths 2/11/2020 Sound of Music 3 42 3D Anatomy of Mouse Brain Reconstruction of All 89 Neurons (with axons) Tiny Cube from Mouse somatosensory cortex 5 Example Neurons with axons Motta et. Al. Max Planck Inst. for Brain Research (Nov 2019) 34,221 Axons Total length 2.7m 2/11/2020 Sound of Music 3 43 Using 2 Ears: Sound Localization in Superior Olive Lateral Superior Olive (LSO) Neurons Compute Left-Right Intensity Difference (High f) Medial Superior Olive (MSO) Neurons Compute Left-Right Arrival Time Difference (Low - Medium f) 2/11/2020 Sound of Music 3 44 Vertical Sound Localization via Frequency Notches in White Noise Pinna— Highly Asymetric 2/11/2020 Sound of Music 3 45 Example of 3D Auditory Neural Spatial Organization: Small region in Cat Inferior Colliculus “Pitch” Neuron 100 Hz Periodicity ~20 Hz ~500 Hz 1.8 kHz f 1.95 kHz → Gerald Langner, The Neural Code of Pitch and Harmony 2.1 kHz (2015) 30 Planar Layers, each receiving input 2.1→2.4 from a narrow section of the 2.4→2.8 Basilar Membrane 2.8→3.3 3.3→3.9 1/27/20 Sound of Music 1 46 OLLI-Vote 2020 Wands NO MAYBE BAD YES ??? GOOD 2/11/2020 Sound of Music 3 47 Can We Hear Phases? WaveGen Fixed Harmonic Phases Hear the Difference? C4 [262 Hz] YES NO Random Harmonic Phases 3/2/2017 Hear All About It 48 What If We Combine Lots of Pure Tones? 300 and 300.3 Hz 4 All at once: 3 2 ① Phases: Random 1 0 300 Hz 0 5 10 15 20 25 30 35 40 45 -1 ② Phases: In Phase -2 -3 at Center -4 P1 P2 1001 Tones: 599.7 and 600 Hz 4 300 to 600 Hz 3 3 sec long 2 1 0 600 Hz 0 5 10 15 20 25 30 35 40 45 -1 -2 -3 -4 P4 P5 3/2/2017 Hear All About It 49 Spectrograms for 1001 Tones ① Phases: Random ② Phases: In Phase at Center 3/2/2017 Hear All About It 50 So Why Can We Detect Phase in One Case … and Not the Other? 3/2/2017 Hear All About It 51 It’s the Basilar Membrane, Stupid Critical Bands Low f High f Basilar Membrane Response Relative Amplitudes 1600 Hz 800 Hz 400 Hz 200 Hz Thus individual Partials are detected by different hair cells and do not interfere.
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