1 / 60

Rob van der Willigen ~robvdw/cnpa04/coll1/AudPerc_2007_1

Auditory Perception. Rob van der Willigen http://~robvdw/cnpa04/coll1/AudPerc_2007_1.ppt. Today’s goals. Outline of The Course. Introduction to the field of Auditory Perception. Understanding the physical nature of sound. General Outline P1-P2. P1: Auditory Perception.

dacia
Download Presentation

Rob van der Willigen ~robvdw/cnpa04/coll1/AudPerc_2007_1

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Auditory Perception Rob van der Willigen http://~robvdw/cnpa04/coll1/AudPerc_2007_1.ppt

  2. Today’s goals Outline of The Course Introduction to the field of Auditory Perception Understanding the physical nature of sound

  3. General Outline P1-P2 P1: Auditory Perception - The Problem of Audition - The Physical Characteristics of Sound P2: The Mammalian Auditory System - Mechanotransduction - Neuroanatomical organization

  4. General Outline P3-P5 P3-P5: Sound Localization - Neural Correlates in Birds and Mammals - Plasticity and Development - Coordinate Transformation - Measuring Sound Localization Behaviour

  5. General Outline P6-P10 P6-P10: Perceptual Dimensions of Hearing - Psychophysics: Measuring Perception - Perception of Sound Level & Loudness - Masking & Critical Band - Illusions & Scene Analysis

  6. Assignments Individual Assignments: - Reading (research papers) - Writing Succinct Essays Group assignments (Pairs): - Write Matlab Scripts - Write Brief Data Reports

  7. Examinations Students must complete all assignments with a satisfactory record. All assignments must be typed and completed within one week. Grading will occur within one week. Students will take a written, final exam with open, closed book questions.

  8. P1: Psychology of Hearing Rob van der Willigen http://~robvdw/cnpa04/coll1/AudPerc_2007_1.ppt

  9. Audition (Hearing)‏ “Detecting and recognizing a sound are the result of a complex interaction of physics, physiology, sensation, perception and cognition.” John G. Neuhoff (Ecological Psychoacoustics 2004; p. 1)

  10. Psychoacoustics Auditory Perception or Psychoacoustics is a branch of Psychophysics. Psychophysics studies relationships between perception and physical properties of stimuli.

  11. Physical vs. Perceptual Dimensions Physical Dimensions: Fundamental measures of a physical stimulus that can be detected with an instrument (e.g., a light meter, a sound level meter, a spectrum analyzer, a fundamental frequency meter, etc.). Perceptual Dimensions: These are the mental experiences that occur inside the mind of the observer. These experiences are actively created by the sensory system and brain based on an analysis of the physical properties of the stimulus. Perceptual dimensions can be measured, but not with a meter. Measuring perceptual dimensions requires an observer.

  12. Psychoacoustics Psychoacoustics is the study of subjective human perception of sounds. Psychoacoustics can be described as the study of the psychological correlates of the physical parameters of acoustics. Acoustics is a branch of physics and is the study of sound.

  13. Sensory Coding and Transduction

  14. Sensory Coding and Transduction A Sensor Called Ear

  15. Sensory Coding and Transduction Peripheral Auditory System Outer Ear: - Extents up to Eardrum - Visible part is called Pinna or Auricle - Movable in non-human primates - Sound Collection - Sound Transformation Gives clues for sound localization

  16. Sensory Coding and Transduction Peripheral Auditory System +60 +40 +20 Elevation (deg) 0 -20 -40 Frequency The Pinna creates Sound source position dependent spectral clues. “EAR PRINT”

  17. Sensory Coding and Transduction Peripheral Auditory System Middle Ear: (Conductive hearing loss) - Mechanical transduction (Acoustic Coupling) - Perfect design for impedance matching Fluid in inner ear is much harder to vibrate than air - Stapedius muscle: damps loud sounds Three bones (Ossicles) A small pressure on a large area (ear drum) produces a large pressure on a small area (oval window)

  18. Sensory Coding and Transduction Peripheral Auditory System Inner Ear: The Cochlea is the auditory portion of the ear Cochlea is derived from the Greek word kokhlias "snail or screw" in reference to its spiraled shape, 2 ¾ turns, ~ 3.2 cm length

  19. Sensory Coding and Transduction Peripheral Auditory System The cochlea’s core component is the Organ of Corti, the sensory organ of hearing Cochlear deficits cause Sensorineural hearing loss

  20. Sensory Coding and Transduction Peripheral Auditory System The Organ of Corti mediates mechanotransduction: The cochlea is filled with a watery liquid, which moves in response to the vibrations coming from the middle ear via the oval window. As the fluid moves, thousands of hair cells are set in motion, and convert that motion to electrical signals that are communicated via neurotransmitters to many thousands of nerve cells.

  21. Sensory Coding and Transduction Peripheral Auditory System

  22. Sensory Coding and Transduction Peripheral Auditory System The organ of corti is the hearing sense organ and lies on the BM (basilar membrane) It consists of supporting cells and hair cells 2 groups of hair cells: inner and outer hair cells Protruding from each hair cell are hairs called stereocilia The tectorial membrane lies above the stereocilia, shearing motion between BM and tectorial membrane causes stereocilia to be displaced

  23. Sensory Coding and Transduction Peripheral Auditory System The auditory nerve consists of vestibular and cochlear nerve Cochlear nerve: the axon fibres of neurons whose cell bodies are in the spiral ganglion of the cochlea. Dendrites of these neurons synapse with the hair cells. The cochlear nerve transmits hearing information from cochlea to central nervous system. Important findings from recording impulses in single auditory nerve fibres are: Spontaneous firing, frequency selectivity of fibres, phase locking.

  24. Sensory Coding and Transduction Peripheral Auditory System Six basic steps:

  25. The Problem of Hearing Now we know the sensor of the process called hearing. It leaves open, however, the question of how sound is actually encoded at the sensory level. ‏

  26. The Problem of Hearing “Only by being aware of how sound is created and shaped in the world can we know how to use it to derive the properties of the sound-producing events around us.” Albert S. Bregman (Auditory scene analysis, 1999; p. 1)‏ ‏

  27. The Adequate Stimulus to Hearing Sound is a longitudinal pressure wave: a disturbance travelling through a medium (air/water) http://www.kettering.edu/~drussell/demos.html

  28. The Adequate Stimulus to Hearing Compression Decompression or rarefaction Compression Duration Particles do NOT travel, only the disturbance Particles oscillate back and forth about their equilibrium positions Distance from source http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/u11l2a.html

  29. The Adequate Stimulus to Hearing Type of waves Transverse waves Longitudinal waves http://www.physics.usyd.edu.au/~gfl/Lecture/GeneralRelativity2005/

  30. Physical Dimensions of Sound Amplitude (A) High http://www.physpharm.med.uwo.ca/courses/sensesweb/ LOUD sound Large change in amplitude Pressure Amplitude Low SOFT sound Small change in amplitude Time or Distance from the source In air the disturbances travels with the 343 m/s, the speed of sound Amplitude is a measure of pressure

  31. Physical Dimensions of Sound Frequency (f) ; Period (T) ; Wavelength (λ) LOW pitched sound Lowfrequency Long wavelength Pressure changes are slow HIGH pitched sound Highfrequency Short wavelength Pressure changes are fast One cycle High Pressure Low Time or Distance from source T is the Period (duration of one cycle) λ is wavelength (length of one cycle) f is frequency (speed [m/s] / λ[m]) or (1/T[s])

  32. The Mathematics of Waves The Pure Tone •has infinite duration, but only one frequency •is periodic and has a phase •is known as the “harmonic function”  = 2pf, is the angular frequency [rad/s] j = is phase‏, t is time

  33. The Mathematics of Waves Phase(ϕ) Phase is a relative shift in time or space

  34. The Mathematics of Waves Superposition Waves can occupy the same part of a medium at the same time without interacting. Waves don’t collide like particles. Two waves (with the same amplitude, frequency, and wavelength) are traveling in opposite directions. The summed wave is no longer a traveling wave because the position and time dependence have been separated.

  35. The Mathematics of Waves Superposition Waves can occupy the same part of a medium at the same time without interacting. Waves don’t collide like particles. Waves in-phase (j =0) interfere constructively giving twice the amplitude of the individual waves. When the two waves have opposite-phase (j =0.5 cycle), they interfere destructively and cancel each other out.

  36. The Mathematics of Waves Superposition Most sounds are the sum of many waves (pure tones) of different Frequencies, Phases and Amplitudes. At the point of overlap the net amplitude is the sum of all the separate wave amplitudes. Summing of wave amplitudes leads to interference. Through Fourier analysis we can know the sound’s amplitude spectrum (frequency content).

  37. The Mathematics of Waves Fourier’s Theorem Jean Baptiste Fourier (1768-1830) Any complex periodic wave can be “synthesized” by adding its harmonics (“pure tones”) together with the proper amplitudes and phases. “Fourier analysis” Time domain Frequency domain “Fourier synthesis”

  38. The Mathematics of Waves Fourier’s Theorem Linear Superimposition of Sinusoids to build complex waveforms If periodic repeating

  39. The Mathematics of Waves Fourier synthesis “Saw tooth wave”

  40. The Mathematics of Waves Fourier synthesis “Square wave”

  41. The Mathematics of Waves Fourier synthesis “Pulse train wave”

  42. The Mathematics of Waves Fourier Analysis Transfer from time to frequency domain Time domain Frequency domain Superposition

  43. Physical Dimensions of Sound Summary • Amplitude • - height of a cycle • - relates to loudness • Wavelength (λ) • - distance between peaks • Phase (j ) • - relative position of the peaks • Frequency (f ) • - cycles per second • - relates to pitch

  44. The Problem of Hearing Now we know the sensor of the transduction process called hearing. And we know a little about the physical nature of sound (Acoustics). So it should be possible to understand how sound is encoded at the sensory level. ‏

  45. Outer Hair cells Organ of Corti Inner Hair cell Auditory nerve Basilar Membrane Sensory Coding of Sound

  46. Sensory Coding of Sound Travelling Wave Theory Periodic stimulation of the Basilar membrane matches frequency of sound Travelling wave theory von Bekesy: Waves move down basilar membrane stimulation increases, peaks, and quickly tapers Location of peak depends on frequency of the sound, lower frequencies being further away

  47. Sensory Coding of Sound Place Theory Travelling wave theory von Bekesy: Waves move down basilar membrane Location of the peak depends on frequency of the sound, lower frequencies being further away Location of the peak is determined by the stiffness of the membrane

  48. Sensory Coding of Sound Cochlear Fourier Analysis Periodic stimulation of the Basilar membrane matches frequency of sound High f Med f Location of the peak depends on frequency of the sound, lower frequencies being further away Low f BASE APEX Position along the basilar membrane

  49. Sensory Coding of Sound Sensory Input is Tonotopic Thick & taut near base Thin & floppy at apex TONOTOPIC PLACE MAP LOGARITHMIC: 20 Hz -> 200 Hz 2kH -> 20 kHz each occupies 1/3 of the basilar membrane

More Related