VARIABILITY OF HIGH-FREQUENCY DISTORTION PRODUCT OTOACOUSTIC EMISSIONS MEASURED BY THE SMARTOAE DEVICE: PRELIMINARY STUDY.

Background: Distortion product otoacoustic emissions (DPOAEs) are usually measured in a frequency range up to 8 kHz, although some systems permit measurements up to 16 kHz. For any test to be reliable it is important to determine its repeatability. Therefore in the present study DPOAE recordings were made using the SmartOAE system with a focus on the repeatability of high-frequency DPOAEs. Material and methods: DPOAEs were measured in subjects with normal hearing from 0.25 to 16 kHz. Recordings were made at frequencies of 0.5, 0.75, 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12.5, 14, and 16 kHz. Each recording session consisted of three measurements: the first two performed without removing the probe from the ear (single fit mode), and the third after removing and re-inserting it into the ear canal (multiple fit mode). Recordings from 15 ears were made. Results: In single fit mode, the biggest fluctuations were obtained at 0.75, 8, 11, 12.5, and 14 kHz -- the largest was 2.8 dB. In the multiple fit mode, greater variability was obtained compared to measurements made without removing the probe -- the largest reached 3.4 dB. Conclusions: Even though the measured signals significantly exceeded the noise floor, differences between measurements for some frequencies still reached as high as 3.4 dB. Our work confirms the usefulness of testing very high DPOAE frequencies (>8 kHz), but at the same time some caution is needed when interpreting the results. [ABSTRACT FROM AUTHOR]