Transcript Psychoacoustics

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
• Difference Threshold -- smallest detectable
change in a stimulus
• These 2 Thresholds were the primary questions
in CLASSICAL PSYCHOPHYSICS
Thresholds
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
Thresholds
The Auditory Response Area
Auditory Response Area
• Range of useable hearing-- from threshold
of detection to threshold of feeling/pain
• Also called the DYNAMIC RANGE OF
HEARING
Thresholds
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
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
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
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
Temporal Integration
Brief Sounds: Temporal Integration
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