Amplification restores separated-condition speech thresholds but leaves a residual NH advantage.

Evidence

Thresholds for the colocated conditions (Fig. 2 left panel) were basically independent of amplification level, and for the NH subjects were about 2.5 dB lower than for the HI subjects. Thresholds for the spatially separated condition (middle panel) clearly improved with increasing amplification for both the NH and HI subjects and were maximal for “normal” audibility. However, thresholds for the NH subjects were on average 4.8 dB lower than for the HI subjects. … It appears that under these conditions, a large proportion of the SRM deficit in the HI (and simulated HI) group could be attributed to reduced audibility. — Dijk, Pim van, Physiology, Psychoacoustics and…, 1740