SHORT-TERM REPEATABILITY OF CONTRALATERAL SUPPRESSION OF TRANSIENTLY EVOKED OTOACOUSTIC EMISSIONS: PRELIMINARY RESULTS
W. Wiktor Jedrzejczak, Edyta Pilka, Lukasz Olszewski, Henryk Skarzynski
(Institute of Physiology and Pathology of Hearing, Warsaw, Poland)
JHS 2016; 6(2): 51-57
The effect of suppression of otoacoustic emissions (OAEs) by contralateral acoustic stimulation (CAS) is very small, on the level of 1–2 dB. At the same time, OAEs are known to have quite high variability across subjects and some fluctuation of the signal between measurements is also present. The purpose of the present study was to investigate short-term repeatability of contralateral suppression of transiently evoked OAEs (TEOAEs).
MATERIAL AND METHODS: OAEs were recorded in a group of 10 adults with normal hearing. TEOAEs were recorded using the linear protocol (all stimuli at the same level and polarity); stimulus levels were kept at 65 dB peSPL; and a 60 dB SPL broadband noise was delivered to the contralateral ear as suppressor. Each recording session consisted of three measurements: the first two were made consecutively without taking out the probe (‘single fit’ mode); the third measurement was made after taking out and refitting the probe (‘multiple fit’ mode). Global and half-octave values of TEOAE response levels and suppression were investigated. Additionally, as a measure of reliability, standard errors of measurement (SEMs) were analyzed.
RESULTS: Broadband suppression was on average around 0.9 dB, while in the three half-octave frequency bands between 1 and 2 kHz it was 1.2–0.9 dB, 0.6 dB for the 2.8 kHz band, and 0.4 dB for the 4 kHz band. The SEM of suppression for single fit mode was about 0.15 dB for broadband analysis and 0.3 dB for 1 kHz, 0.2 dB for 1.4–2 kHz, 0.3 dB for 2.8 kHz, and 0.4 dB for 4 kHz. For multiple fits, there were only minor differences in SEM between broadband and 1–2.8 kHz, while for 4 kHz the SEM was greater, reaching 0.5 dB.
CONCLUSIONS: For a given paradigm, the reliability of suppression of TEOAEs is quite satisfactory for global values and for the 1–2 kHz bands. In this range, the SEM is smaller than the suppression effect. On the other hand, for higher frequencies, the variability is higher, about the same as the measured suppression.
Keywords: Audiology, Hearing Tests, Otoacoustic Emissions, Spontaneous