AGE-RELATED-CHANGES IN EVOKED OTOACOUSTIC EMISSION IN NORMAL-HEARING EARS

The evoked otoacoustic emissions (e-OAEs) elicited by both tone-bursts and clicks were investigated in normal-hearing ears of three age grou ps: young age group (similar to 30 years), middle age group (31 simila r to 50 years) and old age group (51 years similar to). The pseudothre shold of tone-burst e-OAE at stimulus frequencies between 500 Hz and 2 kHz was significantly elevated in the middle and old age groups compa red with that in the young age group. When the relationship between av eraged emission cochleograms drawn from the mean pseudothresholds of t one-burst e-OAEs at 6 stimulus frequencies between 500 Hz and 4 kHz an d averaged pure-tone audiograms was analyzed, a clear difference was f ound among the three age groups in a frequency range between 500 Hz an d 2 kHz. Total echo power, reproducibility, highest peak power and fre quency area peak power up to 4 kHz in click e-OAE significantly decrea sed in the middle and old age groups compared with those in the young age group. These results indicate the possibility that the function of cochlear micromechanics deteriorates in all cochlear partitions with increasing age, even in normal-hearing ears.