A theoretical analysis of the effects of auditory impairment on intensity discrimination

The effect of cochlear hearing loss on intensity discrimination has been experimentally investigated and reported in the literature. It has been observed that the impairment configuration has a significant effect on a subject´s discrimination abilities. In some cases, intensity discrimination for an impaired individual is near-normal at equal SPLs, whereas in other cases, the difference limen is elevated. It has been hypothesized that the near-normal performance of some impaired individuals may be due to either greater intensity resolution (resulting from loudness recruitment) or to the normal spread of excitation. In this paper, we simulate an experiment conducted by Schroder et al. (1994) devised to test these hypotheses. Using a signal detection theory-based approach in combination with a computational auditory model, we are able to replicate their experimental results. Additionally, by manipulating the model, we are able to demonstrate theoretically that the observed behavior results from the spread of excitation.