Differentiation of types of presbycusis using the masking-level difference.

Masking-level differences in quiet at 500 Hz were used to demonstrate evidence of elevated noise levels within the auditory systems of subjects with assumed neural presbycusis. The following five groups of subjects were evaluated: normal-hearing young and old adults; and older adults with metabolic, sensory, or neural presbycusis. The group with assumed neural presbycusis--that is, bilateral high-frequency sensorineural hearing loss and poor word-recognition performance--had masking-level differences (a) in quiet that were significantly larger than those for the other groups and (b) in noise that were significantly smaller than those for the other groups. The data suggest that elevated internal noise levels accompany neural presbycusis.