Intensity and loudness

1
Intensity and loudness

• Lecture 5

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Equal loudness contours. Each curve shows sounds
that are equally loud to the listener. The lower
(red) curve represents the just-audible level
(threshold of hearing)
3
What contributes to the shape of the minimum
audibility curve?
4
Loudness expressed on audiogram for mild hearing
loss. Note the more rapid growth in loudness
(shown by compression of the curves) at high
frequencies
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Loudness (in sones) as function of intensity (in
dB SPL) (similar to fig. 6.3 in your text).
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Measuring intensity jnd

• 1 intensity discrimination
• 2 increment detection
• 3 modulation detection

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Physiological response 1 firing rate of
auditory neurons. Note the difference between
the low spont high spont fibers but for both,
firing rate increases as input intensity
increases, until saturation
But this mechanism alone is not sufficient to
account for the dynamic range over which we can
encode loudness
8
Contribution of high spont low spont fibers to
intensity coding
9
Physiological response continued

• 2 spread of excitation in the cochlea
• 3 pattern of neural response changes (more
  phase locking) with increased intensity