Change in auditory threshold and loudness perception at Fc and bDLF after three months of auditory rehabilitation.

The significant effect of frequency on auditory threshold observed here simply reflects the audiograms of these subjects, whose hearing thresholds were better on low than on high frequencies. The frequency effect on bDLF doubtless derives from the same phenomenon: subjects' auditory thresholds were better at the lowest frequency (fref) than at the highest (bDLF+1/8).

A significant effect of frequency was also observed in the loudness-scaling measurements. Less intensity was necessary for high frequency tones to be perceived as being as loud as the reference frequency. This observation is also reported in presbycusic subjects, and may be explained by a loudness recruitment phenomenon (Fowler, 1936; Steinberg and Garner, 1937) whereby sensorineural hearing-impaired subjects are able to hear loud sounds in the same way as normal-hearing listeners, but sounds that are even louder become uncomfortable to listen to, since the dynamic range of hearing is reduced.

No significant difference with auditory rehabilitation time-course was found for auditory thresholds or for loudness perception: i.e., the auditory abilities of the subjects did not vary between the two parts of the experiment.