2. All you have is a pair of instruments (basilar membranes) that measure air pressure fluctuations over time Localization

3. There are several clues you could use: Localization

4. Left Ear Right Ear Compression Waves

5. There are several clues you could use: 1 arrival time - sound arrives first at ear closest to source Localization

6. Left Ear Right Ear Compression Waves

7. There are several clues you could use: 1.arrival time 2.phase lag (waves are out of sync) - wave at ear farthest from sound source lags wave at ear nearest to source Localization

8. Left Ear Right Ear Compression Waves

9. What are some problems or limitations? Localization

10. Low frequency sounds aren’t attenuated by head shadow Localization Left Ear Right Ear Compression Waves Sound is the same SPL at both ears

11. High frequency sounds have ambiguous phase lag Localization Left Ear Right Ear Left Ear Right Ear Two locations, same phase information!

12. These cues only provide azimuth (left/right) angle, not altitude (up/down) and not distance Localization Left Ear Right Ear Azimuth

13. Localization Additional cues:

14. Localization Additional cues: Head Related Transfer Function: Pinnae modify the frequency components differently depending on sound location

15. Localization Additional cues: Room Echoes: For each sound, there are 6 “copies” (in a simple rectanguluar room!). Different arrival times of these copies provide cues to location of sound relative to the acoustic space

16. Auditory Scene Analysis Sounds don’t happen in isolation, they happen in streams of changing frequencies How does the system group related auditory events into streams and keep different streams separate?

17. Auditory Scene Analysis Solving this problem is called Auditory Scene Analysis One important principle is proximity –in pitch, time, or spatial location

18. Auditory Scene Analysis Effect of timing proximity: SlowFast

19. Auditory Scene Analysis Effect of timing proximity: Pitch Do you hear this? Pitch Or this? SlowFast

20. Auditory Scene Analysis Effect of pitch proximity: closefar

21. Auditory Scene Analysis Effect of pitch proximity: Pitch Do you hear this? Pitch Or this? closefar

22. Auditory Scene Analysis Effect of proximity: –auditory system groups together events that happen close together in time and frequency

23. Pitch and Music

24. Pitch Pitch is the subjective perception of frequency time -> Air Pressure Period - amount of time for one cycle Frequency - number of cycles per second (1/Period)

25. Pitch Pure Tones - are sounds with only one frequency f = 400 hz f = 800 hz

26. Tone Height Tone Height is our impression of how high or low a sound is but there’s something more to our impression of how something sounds than just its tone height…

27. Chroma Tone Chroma is the subjective impression of what a tone sounds like Notes that have the same Chroma sound similar 400 hz 500 Hz 800 Hz

28. Chroma Tones that have the same Chroma are octaves apart

29. Chroma chroma is best represented as a helix chroma repeats every octave tones with the same chroma are above or below each other on a helix

30. Chroma Tones that are octaves apart have the same chroma one octave is a doubling in frequency

31. Chroma frequency is determined (in part) by location of stimulation on the basilar membrane

32. Chroma frequency is determined (in part) by location of stimulation on the basilar membrane but that relationship is not linear (it’s logarithmic)

33. Chroma doublings of frequency map to equal spacing on the basilar membrane