Week 4, Part 1 & 2 Auditory Perception PDF

Week 4, Part 1 Auditory Perception 1  Part I Outline Physical properties of sound and perceptual correlates Sound processing in the ear Neural pathways of sound and their role in auditory perception Auditory scene analysis...

Week 4, Part 1 Auditory Perception 1  Part I Outline Physical properties of sound and perceptual correlates Sound processing in the ear Neural pathways of sound and their role in auditory perception Auditory scene analysis 2  What is sound? Air molecules Compression Rarefaction + - Sinusoidal sound wave 3 https://www.mediacollege.com/audio/01/sound-waves.html https://musiclab.chromeexperiments.com/Sound- Waves/ 4  Perceptual Correlates of Physical Features of Sound Physical Property = Frequency (Hz) Period High frequency wave Perceptual Property = Pitch Amplitude Hz = measures cycles Time (periods) per second 1 second Ex: 50 Hz = 50 cycles (periods) per second Period Low frequency wave 50 Hz higher pitch Amplitude than 25 Hz Time 1 second 5  Perceptual Correlates of Physical Features of Sound Physical Property = Amplitude Perceptual Property = (dB) Loudness Low Amplitude High Amplitude 6 Equal loudness contours: Frequency and intensity determine loudness perception Sound Pressure Level (dB) Phon = measure of loudness perception Ex: 40 phon is louder than 20 phon Frequency (Hz) 7  Part I Outline Physical properties of sound and perceptual correlates Sound processing in the ear Neural pathways of sound and their role in auditory perception Auditory scene analysis 8 Task of the auditory system: Receive mechanical sound wave and make it comprehensible to an organism 9 Outer Middle Ear Inner Ear 10 Outer Ear 11  Morphology matters for auditory perception Morphology = structure/shape Head-Related Transfer Function: Shape of ears, head, and shoulders affects sound perception Different frequencies are amplified Frequencies are amplified differently 12  Outer Ear Like a funnel for sound 13  Divides Outer Ear and Middle Ear Tissue that vibrates when sound waves hit it Transduction 14  Middle Ear Tube filled with fluid Connects to back of nose/throat 15  Middle Ear Chain of small Incus bones Malleus Transmit sound from ear drum to cochlea Stapes 16  Divides Middle Ear from Inner Ear Oval window Connects ossicles to cochlea Stapes 17  Inner Ear Coiled, fluid filled tubes Question: Why can’t sound waves just hit the cochlea? 18 Basilar Membrane Basics 19 https://legacy.cs.indiana.edu/~port/teach/641/audition.for.linguists.Sept1.ht  Tonotopic Coding Sound Amplitude Basilar Membrane https://app.tophat.com/e/628694/content/963 Deflection 20 934::da39e4da-baa9-5303-b324-  Hair cells transduce mechanical signal into electrical signal Loui (nd) 21 Adapted from Wang & Zhou, 2021 Hair cells transduce mechanical signal into electrical signal Lead to auditory nerve firing Auditory nerve firing Adapted from Swenson, 2017 22  Part I Outline Physical properties of sound and perceptual correlates Sound processing in the ear Neural pathways of sound and their role in auditory perception Auditory scene analysis 23 Auditory Auditory information information 24  Key function: Crossing point for auditory nerve https://teachmeanatomy.info/neuroanatomy/pat 25 hways/auditory-pathway/ Auditory Auditory information information 26  Key Function: Binaural hearing Key for sound localisation https://teachmeanatomy.info/neuroanatomy/pat 27 hways/auditory-pathway/  Two cues for locating sounds in space Interaural time difference Interaural level difference Relation of anatomy to function 28 Schnupp, Israel, & Nelken, Auditory Auditory information information 29 Key Function: Sensory integration Orienting Response: Loud sound -> turn and look 30 Auditory Auditory information information 31  Auditory nerve projects to primary auditory cortex Auditory cortex http://humanphysiology.academy/Neurosciences% 32 Breedlove, Watson, & Rosenzweig, 202015/Chapter%203/A.3p%20Auditory%20Pathwa  Part I Outline Physical properties of sound and perceptual correlates Sound processing in the ear Neural pathways of sound and their role in auditory perception Auditory scene analysis 33 How do we perceive different sounds? 34 How many sounds do you hear? What sounds do you hear? How did we just do this? 35  Auditory Scene Analysis Transform sound waves into meaningful auditory “units” Mental representation of sound Key principle Perceptual outcome https://www.noisyplanet.nidcd.nih.gov/sites/noisyplanet/file s/ContentImages/HaveYouHeard/Tribeca_district_NY.jpg Sounds come Grouping from the same source Gestalt principles revisited 36 Schnupp, Isreal, & Nelken, 2011  Rule #1: Temporal Grouping Sequential integration: Connect sounds in time Create auditory streams Physical cues: Temporal proximity, frequency When do you need to do this? https://auditoryneuroscience.com/scene-analysis/streaming-alternating-tones 37  Rule #2: Pitch/Harmonic Grouping Recall 38  Rule #2: Pitch/Harmonic Grouping Fundamental frequency Fundamental frequency: Lowest frequency component Harmonics: Multiples of the fundamental frequency Influence what we hear Second Third harmonic harmonic Challenge: Do a bunch of First harmonic frequencies come from the same source? 39 Mohamed et al., 2017  Rule #2: Pitch/Harmonic Grouping Target frequency Shift harmonics around the target frequency What happens? 40 https://webpages.mcgill.ca/staff/Group2/abregm1/web/downloadstoc.htm#speint 5 min break 41  Week 4, Part II Introduction to Music Perception/Cognition 42  Outline What is music? Key components in music perception Pitch + related components Rhythm + related components 43  Learning Outcomes Consider what music is! Identify key features of pitch and rhythm perception Explain current theories of pitch and rhythm perception 44 Sound = a physical thing with physical properties, that we hear So…what is music? 45 Submit to W05-MusEx 46  Perceptual Components of Music “Spatial” “Temporal” components components Pitch Rhythm Harmony Beat Timbre Metre 47  We hear the “Fundamental Frequency” as pitch Fundamental frequency: The lowest frequency in a sound Perceptual correlate: The tone (pitch) we hear! Processing takes place to perceive pitch Even when NO fundamental frequency is present, we still hear it Missing F0 phenomenon 48 https://auditoryneuroscience.com/index.p hp/pitch/missing-fundamentals Missing Fundamental Frequency Example  How does the missing fundamental frequency work? Fundamental Has to do with harmonics Frequency Predictable frequencies related to the fundamental frequency Second harmonic Extract information about the Third fundamental frequency from the harmonic harmonics, even when the fundamental frequency is missing Fourth harmonic 50  Pitch perception is stable across… Loudness levels 30 dB 50 dB 200 Hz 200 Hz Pitch perception is stable across… Spatial location  Pitch perception is stable across… Flute Levels of harmonics Horn Frequency Frequency Oboe Frequency Time Time https://auditoryneuroscience.com/i ndex.php/pitch/melodies-timbre Time  Different harmonic levels create different timbres Flute Specific quality of Horn the sound Frequency Frequency Oboe Frequency Time Time https://auditoryneuroscience.co m/index.php/pitch/melodies- timbre Time  Theories of pitch perception Place Theory: Peaks in activity along the basilar membrane determine pitch percept Recall: Tonotopic coding Peripheral processing Time Theory: Rates of neural firing determine pitch percept Recall: Subcortical firing rates Central processing Auditory nerve firing rate  Theories of pitch perception Both theories have been supported Place Theory: Higher frequencies can be encoded by place Time theory: Lower frequencies can be encoded by neural firing rates Volley theory: Groups of neurons encode the rate  What is rhythm? Rhythms = things that repeat in time and can be anticipated1 https://en.wikipedia.org/wiki/Neural_oscillation#/media/File:SimulationNeuralOscillations.png 1Fraisse, 1982  Auditory rhythms = Stable gaps between tones that repeat We perceive sound patterns using a few different cues1 Change relative timing of tones Change amplitude of every second tone Change pitch of every second tone 1McAuley, 2006  Tempo influences rhythm perception Temporal integration window: Optimal time window in which we bind stimuli into a single percept Discrete sounds -> rhythm < 100 ms = no xxxxxxxxxx rhythm percept > ~2 sec = no rhythm x x x x x x x x x x percept 100 ms < Rhythm < ~ 2 sec x x x x x x x x x x  Core features of rhythms in music perception Key temporal features of auditory rhythms: Tempo, beat, metre Beat = consistent periodic time point in an auditory rhythm Pulse = perceived beat -> move at the beat level  Core features of rhythms in music perception Metre = pattern of accented beats in a rhythm2 Ex. Duple/quadruple (march), triple (waltz) Hierarchical Perceived metre = beats on many timescales Timescales align = stronger beat 2Stalinski & Schellenberg, 2012  Core features of rhythms in music perception Perceived metre = beats on many timescales Timescales align = perceive stronger beat Weakest beat Faster level Beat level Slower level Strongest beat Large et al. (2015) 1. Clap on the beat 2. Clap at a faster (higher) level than the beat 3. Clap at a slower (lower) level than the beat 63  Theories of Rhythm Perception Interval theories: A running count of time going by Compare how much time has gone by between A and B, and B and C to perceive and make judgements about time Entrainment theories: Rhythmic neural activity entrains to rhythmic auditory stimuli Rhythmic neural firing patterns used to perceive and make judgements about time  Interval Theories Start Count End Count 5 seconds Start Count End Count 10 seconds Compare: vs  Interval Theories Tone 1 Tone 2 Start Count End Count 400 ms Tone 2 Tone 3 Start Count End Count 800 ms Compare: vs Entrainment = coupling in time  Entrainment Theories How entrainment theory works: Neurons are firing rhythmically Auditory rhythm comes on Correspondence (coupling) between neural rhythm and auditory rhythm? Judge time by 1) the alignment between neural and auditory rhythms and 2) the rate (speed) of neural rhythms  Recap Pitch Fundamental frequency and missing F0 Stability of pitch Theories of pitch perception Rhythm Perceptual cues Beat, pulse, and metre Theories of rhythm perception 69