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SPHSC 462 HEARING DEVELOPMENT Overview Review of Hearing Science Introduction 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). Exams Take-home Essay Open book Must work alone; penalty for breaking this rule is failing grade 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. Drop boxes Your discussion questions: https://catalysttools.washington.edu/collectit/drop box/lawerner/7177 Take-home exams https://catalysttools.washington.edu/collectit/drop box/lawerner/7143 Review of Hearing Science Hearing in a nutshell Wow! Psychophysics is interesting! FREQUENCY TIME What are the characteristics of sound represented in the auditory nerve response? Intensity Frequency Temporal characteristics (changes in intensity or frequency over time) How does the ear come to represent these characteristics of sound? Conduction Transduction Traveling wave and Active Mechanism Conduction Frequency (Hz) Frequency (Hz) Frequency (Hz) Frequency (Hz) Transduction: changing acoustic energy to electrochemical energy A B C E D F QuickTime™ and a Animation decompressor are needed to see this picture. Where does the code for intensity come from? QuickTime™ and a Animation decompressor are needed to see this picture. Low level QuickTime™ and a Animation decompressor are needed to see this picture. High level Combined firing rate of auditory nerve fibers with the same best frequency Where does the code for frequency come from? QuickTime™ and a Sorenson Video decompressor are needed to see this picture. Hair cell potential 0 Time Time Spikes Pressure Coding of the time waveform of sound: Tone Time Hair cell potential 0 Time Time Spikes Pressure Coding of the time waveform of sound: Complex waveform Time Hair cell potential 0 Time Time Spikes Pressure Coding of the time waveform of sound: High frequency tone Time Hair cell potential 0 Time Time Spikes Pressure Coding of the time waveform of sound: High frequency complex Time Where does the code for frequency come from? For low frequencies, a code for frequency is carried in the timing of auditory nerve action. Where does the code for temporal characteristics come from? QuickTime™ and a Sorenson Video decompressor are needed to see this picture. Pressure Pressure Coding of the time waveform of sound: Temporal characteristics 0 0 Time Spikes Spikes Time Time Time Traveling wave and active mechanism The other code for frequency Basilar membrane motion Base Apex Traveling wave QuickTime™ and a Sorenson Video decompressor are needed to see this picture. QuickTime™ and a Sorenson Video decompressor are needed to see this picture. Traveling wave QuickTime™ and a Animation decompressor are needed to see this picture. The active mechanism How are these three characteristics of sound represented in the auditory nerve response? 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 So the message in the auditory nerve is sort of like a spectrogram FREQUENCY = POSITION OF AN FIBER ALONG BASILAR MEMBRANE TIME Hearing in a nutshell Wow! Psychophysics is interesting! FREQUENCY TIME Sound source segregation FREQUENCY TIME 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 Hearing in a nutshell and sound source segregation Wow! Psychophysics is interesting! FREQUENCY TIME Acoustic cues used in localization Interaural intensity differences Interaural time differences Spectral shape cues For next time Read p. 1-14 of “Human auditory development” chapter, Intro and Frequency representation