RELATIONSHIPS BETWEEN THE VARIABILITY OF MAGNITUDE MATCHING AND THE SLOPE OF MAGNITUDE LEVEL FUNCTIONS

Binaural loudness matching and intermodal magnitude matching experimen ts were performed to test systematically the origins of the phenomenon observed earlier that the variability of binaural loudness matches wa s larger when sound intensity was varied in the normal ear than when i t was varied in the contralateral ear with raised threshold and loudne ss recruitment. In the experiments, the raised threshold and loudness recruitment were produced by masking a 1-kHz tone with narrow-band ran dom noise. In intermodal experiments, magnitude matches were performed between the masked tone and the length of lines projected on a transl ucent window pan. The results are consistent with the earlier observat ions. They show in addition that the variability depends on the slope of the matching functions in a complicated, not previously anticipated way, irrespective of whether the functions are intra- or intermodal. More specifically, for moderate slopes, the variability in the ear wit h loudness recruitment decreased as the slope increased. The reverse w as true for the unmasked ear or the line length-when the slope was lar ge, the variability increased with the slope. Since the variability de creased in one ear and increased in the other, the ratio of the variab ilities increased as the slope increased. When the slope was equal to one, both variabilities tended to be the same.