Building upon the classical works of Weber and Fechner in the last century about relative perceptual thresholds, which culminated in the model of the logarithmic law, a better fit to the experimental data for a number of sensory channels has been demonstrated by Stevens with a psychophysical power law [325]:
where 
is the subjective magnitude, S is the physical stimulus
intensity and m is a modality-dependent exponent.
Table 1.3
Table 1.3
: Exponents for the psychophysical law (taken
from [325])
Esprit Project 8579/MIAMI (Schomaker et al., '95)