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Psychoacoustics: Sound Perception

Psychoacoustics: Sound Perception. Physics of Music, Spring 2014. Key Terms. Anatomical Terms Tympanic membrane Ossicles Bony Labyrinth Cochlea Basilar membrane Organ of Corti/Hair cells Place theory of hearing Critical band Sharpening Sound Intensity Level Decibel scale

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Psychoacoustics: Sound Perception

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  1. Psychoacoustics: Sound Perception Physics of Music, Spring 2014

  2. Key Terms • Anatomical Terms • Tympanic membrane • Ossicles • Bony Labyrinth • Cochlea • Basilar membrane • Organ of Corti/Hair cells • Place theory of hearing • Critical band • Sharpening • Sound Intensity Level • Decibel scale • Just Noticeable Difference (JND) • Subjective Loudness • Ohm’s Law of Hearing • Attack and decay transients • Pitch tracking • Missing fundamental • Masking • Binaural Effects

  3. How do we “hear”?

  4. Anatomy and Physiology: Form and Function Video produced by Brandon Pletsch, Univ. of Georgia Medical School URL: http://www.youtube.com/watch?v=N90j2h3M0ic

  5. Auditory system: Amazing facts • 10 octave range (20 – 20,000 Hz) Ear senses changes 1 part of10,000,000,000 of atmospheric pressure

  6. Auditory Cortex Saenz Auditory Neuorscience Group: http://www3.unil.ch/wpmu/neuroaudio/resaerch/auditory-cortex/ Reference: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0017832 URL: http://www.youtube.com/watch?v=N90j2h3M0ic

  7. How do we know? Answer: fMRI Ginormous magnetic coil • Hemoglobin carries oxygen • 2. Hemoglobin is magnetic (Iron atom!) • 3. Brain uses oxygen where active • 4. Therefore, magnetic signal tells you where your brain is active Image source (top): Univ. of Indiana http://blogs.oem.indiana.edu/scholarships/wp-content/uploads/2009/10/fmri_groot.jpg Image source (bottom): https://gustavus.edu/events/nobelconference/2011/teachers/files/fMRIbackground.pdf

  8. Place Theory Perception of sound depends on which region (place) of basilar membrane vibrates Critical band Images from: http://hyperphysics.phy-astr.gsu.edu/hbase/sound/place.html

  9. JND • Change in value of a variable (frequency, intensity) between two tones such that the difference just noticeable. • For instance: Can you tell the difference between: • 440.0 vs 440.1 Hz? • 440 vs 441 Hz? • 440 vs 444?

  10. SIL = 10 log10 (I1/Io) dB unit = decibel Sound Intensity Level Io = 10-12 W/m2 Factor of 10 increase  10 dB Factor of 2 increase  3 dB 1 dB  I1/Io = 1.25 3 dB  I1/Io = 2 10 dB  I1/Io = 10 20 dB  I1/Io = 100

  11. Sound deciBel scale

  12. Subjective Loudness Sensitivity depends on frequency JE’s Equal loudness Curve Average Equal loudness Curve Hearing test: http://www.phys.unsw.edu.au/jw/hearing.html

  13. Ohm’s Law of Hearing “Sound quality of a complex tone depends only on the amplitude of harmonics, not their phase” Image and sound file source: http://frank.mtsu.edu/~wroberts/ohms.htm

  14. “Turning on” phase is very important for sound perception Attack Transients http://www.animations.physics.unsw.edu.au/jw/timbre-envelope.htm

  15. Pitch Tracking You play these…. You may hear this… The “missing fundamental”

  16. Alien enjoying cocktail party?! Masking How do we pick out one voice amongst all the other masking sounds? Masking: existence of one tone interfering with perception of another tone.

  17. BinauralEffects • It’s all in your head—purely neural processing • Not actual superposition of physical waves

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