FIG. 9.

Tuning characteristics of fmPTCs in normal-hearing and hearing-impaired acoustic listeners, taken from previous work by Nelson (1991), compared with tuning characteristics of fmSTCs obtained from Clarion (monopolar) and Nucleus (bipolar) cochlear implant listeners. Each panel plots a different tuning parameter for three groups of acoustic listeners along with two groups of cochlear-implant listeners. Normal-hearing (NH) acoustic listeners are represented by the black squares; hearing-impaired acoustic listeners with relatively normal tuning (HI) are represented by the black diamonds; hearing-impaired acoustic listeners with abnormal tuning (HIa) are represented by the open circles (abnormal tuning was judged by the HF slope). Cochlear-implant listeners are represented by the shaded circles (Clarion—monopolar) and the shaded triangles (Nucleus—bipolar). The abscissa differs for the acoustic listeners and cochlear-implant listeners. The tuning parameters for the acoustic listeners are plotted as a function of the level (dB SPL) of the acoustic probe used to collect the fmPTC. A wide range of probe levels were tested in both normal-hearing and hearing-impaired listeners but, of course, the range was smaller in hearing-impaired listeners. The tuning parameters for the cochlear-implant listeners are plotted as a function of percent dynamic range (%DRμA) for the probe pulse train. In addition, the geometric means for each group of cochlear-implant subjects are shown by the black circle (Clarion) and black triangle (Nucleus) to the left in (A), (B), and (D). In (C), both the LF slopes (dark-shaded triangles) and HF slopes (light-shaded triangles) of the cochlear implant tuning curves are compared with the Tail slopes (black and open symbols) of the acoustic tuning curves.