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

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