SPHSC 462 HEARING DEVELOPMENT

1. SPHSC 462HEARING DEVELOPMENT Overview Review of Hearing Science Introduction

2. Overview of course and requirements • Lecture/discussion; lecture notes on website http://faculty.washington.edu/lawerner/sphsc462/ • No text; chapter and other readings on website • Requirements: two take-home exams (40% grade each) and discussion questions/in-class discussion of articles (20% grade).

3. Exams • Take-home • Essay • Open book • Must work alone; penalty for breaking this rule is failing grade

4. Article discussion • Articles every week starting Oct 15. • I will provide some questions to guide you through the articles. • You will submit one question about things you didn’t understand, one question that you think it would be interesting to discuss and answer the question, “How is this article relevant to me? by 5:30 am on discussion day.

5. Drop boxes • Your discussion questions: • https://catalysttools.washington.edu/collectit/dropbox/lawerner/7177 • Take-home exams • https://catalysttools.washington.edu/collectit/dropbox/lawerner/7143

6. Review of Hearing Science

7. Hearing in a nutshell Wow! Psychophysics is interesting! TIME FREQUENCY

8. What are the characteristics of sound represented in the auditory nerve response? • Intensity • Frequency • Temporal characteristics (changes in intensity or frequency over time)

9. How does the ear come to represent these characteristics of sound? • Conduction • Transduction • Traveling wave and Active Mechanism

10. Level (dB) Frequency (Hz) Level (dB) Frequency (Hz) Level (dB) Level (dB) Frequency (Hz) Frequency (Hz) Conduction

11. Transduction: changing acoustic energy to electrochemical energy A C D B E F

12. Where does the code for intensity come from? High level Low level Combined firing rate of auditory nerve fibers with the same best frequency

13. Where does the code for frequency come from?

14. Coding of the time waveform of sound: Tone Hair cell potential 0 Pressure Time Spikes Time Time

15. Coding of the time waveform of sound: Complex waveform Hair cell potential 0 Time Pressure Time Spikes Time

16. Coding of the time waveform of sound: High frequency tone Hair cell potential 0 Pressure Time Spikes Time Time

17. Coding of the time waveform of sound: High frequency complex Hair cell potential 0 Pressure Time Spikes Time Time

18. Where does the code for frequency come from? For low frequencies, a code for frequency is carried in the timing of auditory nerve action.

19. Where does the code for temporal characteristics come from?

20. Coding of the time waveform of sound: Temporal characteristics 0 0 Pressure Pressure Time Time Spikes Spikes Time Time

21. Traveling wave and active mechanism The other code for frequency

22. Basilar membrane motion Apex Base

23. Traveling wave

24. Traveling wave

25. The active mechanism

26. Intensity Frequency Temporal characteristics Combined firing rate of auditory nerve fibers with the same CF Place code and temporal code Phase-locking, but with limitations How are these three characteristics of sound represented in the auditory nerve response?

27. So the message in the auditory nerve is sort of like a spectrogram TIME FREQUENCY = POSITION OF AN FIBER ALONG BASILAR MEMBRANE

28. Hearing in a nutshell Wow! Psychophysics is interesting! TIME FREQUENCY

29. Sound source segregation TIME FREQUENCY

30. Cues that could be used to segregate components into sources • Spectral separation • Spectral profile • Harmonicity • Spatial separation • Temporal separation • Temporal onsets and offsets • Temporal modulations

31. Hearing in a nutshell and sound source segregation Wow! Psychophysics is interesting! TIME FREQUENCY

32. Acoustic cues used in localization Interaural intensity differences Interaural time differences Spectral shape cues

33. For next time • Read p. 1-14 of “Human auditory development” chapter, Intro and Frequency representation