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

2. Key Terms Anatomical Terms Tympanic membrane Tympanic membrane Ossicles Ossicles Bony Labyrinth Bony Labyrinth Cochlea Cochlea Basilar membrane Basilar membrane Organ of Corti/Hair cells Organ of Corti/Hair cells Place theory of hearing Critical band Critical band Sharpening Sharpening Sound Intensity Level Decibel scale Decibel scale Just Noticeable Difference (JND) Subjective Loudness Ohm’s Law of Hearing Attack and decay transients Attack and decay transients Pitch tracking Missing fundamental Missing fundamentalMasking 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 Reference: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0017832http://www.plosone.org/article/info:doi/10.1371/journal.pone.0017832 URL: http://www.youtube.com/watch?v=N90j2h3M0ichttp://www.youtube.com/watch?v=N90j2h3M0ic Saenz Auditory Neuorscience Group: http://www3.unil.ch/wpmu/neuroaudio/resaerch/auditory-cortex/

7. How do we know? Answer: fMRI 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 Ginormous magnetic coil 1.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

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

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? 440.0 vs 440.1 Hz? 440 vs 441 Hz? 440 vs 441 Hz? 440 vs 444? 440 vs 444?

10. Sound Intensity Level I o = 10 -12 W/m 2 SIL = 10 log 10 (I 1 /I o ) dB unit = decibel Factor of 10 increase  10 dB Factor of 2 increase  3 dB 1 dB  I 1 /I o = 1.25 3 dB  I 1 /I o = 2 10 dB  I 1 /I o = 10 20 dB  I 1 /I o = 100

11. Sound deciBel scale

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

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. Attack Transients “Turning on” phase is very important for sound perception 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. Masking How do we pick out one voice amongst all the other masking sounds? Alien enjoying cocktail party?! Masking: existence of one tone interfering with perception of another tone.

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