We had each subject listen to 1000 trials per level composed of 6-tone complexes using a 2 AFC loudness paradigm. Subjects voted for the louder interval. For these conditions we were using levels of each 6-tone (6 frequency) complex randomly chosen from a gaussian distribution of levels +- 15 dB from the mean level.
We ran ascending levels for half the subjects and descending for the other half assigned randomly.
Using the 1000 trials we determined the relative "beta" weights by correlating the subject's response (which interval was judged as louder) with the relative local level difference between the levels of each tone. This analysis was a multiple regression, that is based on previously published experiments in our lab.
We determined the weights for each tone in the tone complex per level for each subject and level.
The research question is does the pattern of loudness weights change as a function of frequency, level, or the interaction of frequency by level.
frequency is nested in level. Each level had the same 6 tones. Each subject was given the same combination of conditions.