Discriminability, Loudness, and Masking in the Rat (Rattus norvegicus): A Confirmation and Extension
WALTER REED ARMY INST OF RESEARCH WASHINGTON DC
Pagination or Media Count:
In Experiment 1, rats discriminated between two sound pressure levels SPL of a pure tone standard STD SPLs of 84 and 74 dB and comparison CO SPLs 4, 14, and 24 dB below STD were tested in quiet and 60 dB noise at 4 and 12.5 kHz 24 conditions. The decibel difference between STD and CO accounted for only 43.52 of the variance in the signal detection measure of sensitivity, d, across conditions, whereas the loudness difference LD STD 0.35 - CO 0.35 accounted for 89.82 of the variance in d. These results confirm and extend previous observations that a equal decibel differences are not equally discriminable b loudness for the rat increases as a power function of SPL with an exponent of 0.35 and c masked loudness is a linear function of loudness in quiet. In Experiment 2, the assumptions of normal distribution and equal variance implicit in the use of the d measure were examined.
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