Decrement detection in normal and impaired ears

The smallest detectable duration of a brief decrement in the intensity of wideband noise was measured as a function of the depth of the decrement. In the first experiment, conditions were tested in which the noise before the decrement was more intense than the noise after the decrement, and vice-versa. These data were used to estimate the shape of an intensity-weighting function, or temporal window, describing the temporal resolution of the ear. The equivalent rectangular durations (ERDs) of the temporal windows measured in this way had values of about 5.5, 4.6, and 6.6 ms for noise spectrum levels of 10, 30, and 50 dB, respectively. In a second experiment, decrement detection was measured in subjects with unilateral sensorineural hearing loss. One set of thresholds was measured in the impaired ear, and two sets of thresholds were measured in the normal ear; one with the noise level at equal SPL to the level in the impaired ear, and one with the noise at equal SL. Temporal window shapes were also estimated from these data. Only one of the subjects showed reduced temporal resolution in the impaired ear, the other two subjects having similar ERD values for all three conditions.