The effects of aging on evoked otoacoustic emissions and efferent suppression of transient evoked otoacoustic emissions

Abstract

There is still controversy regarding the effects of aging on the amplitude of evoked otoacoustic emissions (EOAEs), as well as on the efferent system measured by contralateral acoustic stimulation of EOAEs. The purpose of this study was to investigate EOAEs and efferent suppression (ES) with increasing age.Seventy-one ears (20-79 years) were included in the study, 47 of which had normal hearing thresholds, and 24 ears had a sensorineural high-frequency hearing loss caused by presbycusis. The effects of aging on transient evoked (TEOAEs) and distortion product OAEs (DPOAEs), and on ES were evaluated using multiple regression and correlation coefficients. EOAE amplitudes were more strongly correlated with age, than with pure-tone thresholds (PTTs). Moreover, the increase in the amount of variance explained by the regression model using these variables as predictors was larger for PTTs as compared to the variable age.Similar results were found for ES.There might be an age-dependent decline in EOAEs and ES independent from the influence of deteriorating hearing thresholds although the latter superimpose on the effects of age. The relative contribution of age and hearing thresholds on EOAEs, as well as on ES is important for their interpretation in clinical settings.

Development, validation and application of a generator for distortion product otoacoustic emissions

“…A comparison with normative data in clinical conditions [18] showed that for frequencies above 1 kHz (f 2 ), the DPOAE generator is capable of generating realistic responses that are stable in time, apart from expected test-retest variability due to differences in probe placement. Below 1 kHz, the noise level increases considerably and the amplitude of the DPOAE responses falls below the normative data.…”

“…DPOAE responses and not artifacts [5,24]. DPOAE amplitudes produced by the proposed generator fall within the range of normative data obtained on normal-hearing subjects between 18 and 30 years old [18]. Deviations observed for DPOAEs at f 2 frequencies below 1 kHz will be discussed in detail in Section 5.…”

“…The proposed DPOAE generator is a valid alternative for repeated measurements on humans if: 1. the DPOAEs fall within the range of human for two different probe fits (DP fit1, DP fit2). In shaded grey area, normative DPOAE levels are shown, spanning the average DPOAE levels obtained for normal hearing subjects plus and minus one standard deviation [18].…”

“…Although not directly related to the inner ear mechanics, suppressing the primary tones and other third power distortion products substantially improves the DPOAE signal-to-noise ratio. A final gain control (FG) is used to tune the overall DPOAE level to normative data [18]. …”

“…Sections 3 and 4 describe the methodology and results of an extensive validation of the DPOAE generator responses with normative data obtained with the human subjects in the quiet clinical conditions [18]. For this purpose, a newer type of OAE equipment is used compared to the one used in [17].…”