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CHAPTER 10

CHAPTER 10. Auditory Sensitivity. PSYCHOACOUSTICS. A branch of psychophysics The study of the relation between: the physical aspects of sound and the psychological experience of sound. Threshold or Limen. Absolute Threshold -- lowest value of stimulus which can be detected

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CHAPTER 10

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  1. CHAPTER 10 Auditory Sensitivity

  2. PSYCHOACOUSTICS • A branch of psychophysics The study of the relation between: • the physical aspects of sound and • the psychological experience of sound

  3. Threshold or Limen • Absolute Threshold -- lowest value of stimulus which can be detected • Difference Threshold -- smallest detectable change in a stimulus • These 2 Thresholds were the primary questions in CLASSICAL PSYCHOPHYSICS Thresholds

  4. Minimum Audibility Curve-- • Plot of threshold of detection (in dB SPL) as a function of frequency • Lowest thresholds in 1 to 4 kHz region Thresholds

  5. The Auditory Response Area Thresholds

  6. Auditory Response Area • Range of useable hearing-- from threshold of detection to threshold of feeling/pain • Also called the DYNAMIC RANGE OF HEARING Thresholds

  7. Differential Sensitivity • Detecting changes in a stimulus • (e.g., how small a change in frequency can you detect) • Measured as the jnd - just noticeable difference Diff. Sensitivity//Weber’s Law

  8. Weber’s Law--A Theory of human differential sensitivity • Δ S/S = k • Size of jnd = constant fraction of the stimulus you start with • It’s easier to detect small changes in a stimulus if it had a small value to begin with. Diff. Sensitivity//Weber’s Law

  9. Frequency Resolution • The Critical Band reflects “internal filtering”--the ability to attend to a narrow range of frequencies • Remember the tuning curves from Bekesy’s dead ear and the healthy cochlea? • You need the healthy cochlea to have good frequency resolving power

  10. Good Frequency Resolution Allows you to: • Listen to harmonic structure of complex signals • Detect Shifts in Frequency (esp. formant transitions) • Hear and Understand signals in noise

  11. Brief Sounds: Temporal Integration Temporal Integration

  12. Temporal Aspects: TEMPORAL INTEGRATION • A certain amount of energy must be present for detection of a brief signal. • The process of summing energy over time is called integration and it is completed by 300 ms. • If the signal is shorter than 300 ms, then power must be increased for the signal to be detected. Temporal Integration

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