Perceptual Coherence : Hearing and Seeing

248 Perceptual Coherence
the decision process as pictured in figure 6.3. The magnitude and type of
effect of the practice depended on the specific neural pathways and task. In
general, both factors were important. Practice allowed the observers to reduce
the internal additive noise to some degree and to retune the perceptual
template to more completely exclude the external noise.
Adaptation and Gain Control in General
As described previously, the auditory and visual systems face an immensely
wide range of natural intensities, on the order of 10 8 to 10 10 , from moonlight
to sunlight and from the softest sound to the loudest (see table 6.1).
Table 6.1 The Dynamic Range of the Auditory and Visual Systems.
Sound
Intensity Pressure Luminance
(log Level Audition of White Vision Retinal
units) (dB SPL) (watts/m2) Paper in (log cd/m2) Functioning
8 200
7 190 Normal Retinal
Atmospheric Damage
Pressure possible
6 180
5 170 Sunlight Photopic
4 160
3 150 Best
Acuity
2 140 Indoor Color
lighting Vision
1 130 Threshold Rod
of pain Saturation
begins
0 120 Rock Band
−1 110 Moonlight Mesotopic
−2 100 Subway
passing
−3 90 Starlight Cone
−4 80 Loud Radio Threshold
−5 70 Average Poor Scotopic No
Conversation Acuity color
vision
−6 60
−7 50 Average Threshold
Residence
−8 40
−9 30
−10 20 Quiet whisper
−11 10
−12 0 Threshold