Aging and contralateral suppression effects on transient evoked otoacoustic emissions.

Transient evoked otoacoustic emissions (TEOAEs) were recorded in 30 normal-hearing subjects to nonlinear clicks while continuous contralateral broadband noise (CBBN) was presented at 40, 50, 60, and 70 dB HL. Thirty subjects between 20 and 79 years were divided system-atically into six-decade age groups, five subjects per group. All subjects in each group had hearing thresholds of 20 dB HL or better for the test frequencies from 0.25 to 8.0 kHz and normal acoustic immittance findings. The results provide evidence that contralateral suppression at varying levels of CBBN is interactive with age. Except for subjects in the age ranges between 60 and 69 and 70 and 79 years of age, an increase in CBBN from 40 to 70 dB in 10-dB steps resulted in an average increase in suppression from about 0.5 to 3.5 dB SPL. In addition, the contralateral suppression at 60 and 70 dB HL was significantly greater for subjects between 20 and 59 years of age than for subjects between 60 and 79 years of age.