Data gathered by Korman and Weiler [MA thesis, Univ. of Cincinnati, 1986] and Janson et al. [Br. J. Audiol. 30, 35--42 (1996)] have shown the loudness function for loudness adaptation gathered by the ipsilateral comparison procedure (ICP) differs for normal hearing listeners and those with high-frequency cochlear loss. This paper investigates the modeling assumptions for loudness growth in the two kinds of listeners. Surprisingly, the loudness growth within a given frequency is not clearly different in kind, although the two groups start with different values in most test conditions. However, there does appear to be a difference across frequencies which may be a reflection of the spread of excitation on the basilar membrane. Expected differences in activation for normal listeners and those with a high-frequency loss will be discussed.