Loss of cochlear suppression explains similar PTCs across masking conditions.

Evidence

Psychophysical tuning curves obtained in listeners with hearing loss demonstrate poor frequency selectivity as well. The poorer frequency selectivity of the impaired listeners becomes even more apparent when PTCs are measured under conditions of forward masking, as tuning is not sharper under forward masked conditions for listeners with sensorineural hearing loss (Moore & Glasberg, 1986). Wightman, McGee, and Kramer (1977) found that the suppression mechanism is not effective in listeners with sensorineural hearing loss. Recall that in normal-hearing listeners, suppression caused the simultaneously obtained PTCs to be broader than the forward-masked PTCs. Thus, loss of suppression explains why the PTCs are so similar between forward-masked and simultaneously masked conditions. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 567

Categorization

• DEFINE: Explains the suppression mechanism and how forward vs. simultaneous masking distinguishes it — a core concept for the reader’s theory-of-hearing goal.
• XREF: The suppression mechanism here parallels the two-tone suppression discussed in earlier chapters on cochlear mechanics/otoacoustic emissions.