Modulation Detection Interference (MDI) in listeners with cochlear hearing loss.

This study compared Modulation Detection Interference (MDI) in listeners with cochlear hearing loss and in listeners with normal hearing. The study was motivated by questions of temporal resolution in the listeners with cochlear hearing loss as well as by their general difficulty in monitoring target sounds in the presence of competing background noise. The first experiment was similar to the MDI paradigm of Yost and Sheft (1989) and showed an equivalence in performance between the two groups of listeners: MDI brought about by an interfering tone comodulated with the target tone at 10 Hz was about 11 dB in both groups. There was also no difference in MDI magnitude when the modulation rate of the interferer changed to 25 Hz, indicating a lack of tuning to differential modulation rate in the gated paradigm employed here. The second experiment was analogous in concept to the measurement of a psychophysical tuning curve; the depth of modulation of the interfering carrier was adjusted to just interfere with the detection of a suprathreshold degree of modulation on the target carrier. The listeners with cochlear hearing loss performed quite similarly to the normal group, and the general lack of a frequency effect for the carrier tones suggested that MDI was relatively insensitive to presumed differences in auditory filter bandwidth between listeners. Because the basis of MDI has been hypothesized to be the fusion of the interfering tone with the target tone, the results of this study suggest that the auditory grouping factors presumed to underlie MDI are intact in listeners with hearing loss of cochlear origin.