SPHSC 462 HEARING DEVELOPMENT Overview Review of Hearing Science Introduction
Overview of course and requirements Lecture/discussion; lecture notes on website 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: box/lawerner/ box/lawerner/7177 Take-home exams box/lawerner/ box/lawerner/7143
Review of Hearing Science
Hearing in a nutshell TIME FREQUENCY Wow! Psychophysics is interesting!
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) Level (dB) Frequency (Hz) Level (dB) Frequency (Hz) Level (dB) Frequency (Hz) Level (dB)
Transduction: changing acoustic energy to electrochemical energy A B C D E F
Where does the code for intensity come from? Combined firing rate of auditory nerve fibers with the same best frequency Low level High level
Where does the code for frequency come from?
Coding of the time waveform of sound: Tone Pressure Time Hair cell potential Spikes Time 0
Coding of the time waveform of sound: Complex waveform Pressure Time Hair cell potential Spikes Time 0
Coding of the time waveform of sound: High frequency tone Pressure Time Hair cell potential Spikes Time 0
Coding of the time waveform of sound: High frequency complex Pressure Time Hair cell potential Spikes Time 0
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?
Coding of the time waveform of sound: Temporal characteristics Pressure Time Spikes Time 0 Pressure Time Spikes Time 0
Traveling wave and active mechanism The other code for frequency
Basilar membrane motion Base Apex
Traveling wave
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 TIME FREQUENCY = POSITION OF AN FIBER ALONG BASILAR MEMBRANE
Hearing in a nutshell TIME FREQUENCY Wow! Psychophysics is interesting!
Sound source segregation TIME FREQUENCY
Spectral separation Spectral profile Harmonicity Spatial separation Temporal separation Temporal onsets and offsets Temporal modulations Cues that could be used to segregate components into sources
Hearing in a nutshell and sound source segregation TIME FREQUENCY Wow! Psychophysics is interesting!
Acoustic cues used in localization Interaural intensity differences Interaural time differences Spectral shape cues
For next time Read p of “Human auditory development” chapter, Intro and Frequency representation