IPSILATERAL MEASUREMENT OF THE ACOUSTIC REFLEX USING WIDEBAND POWER REFLECTANCE

Abstract

The contraction of the stapedius muscle is known as the acoustic reflex (AR), which stiffens the ossicular chain/ tympanic membrane. Conventional immittance systems only evaluate changes in admittance for the 226 Hz probe tone with AR activation. Conversely, wideband power reflectance (WPR) provides information regarding energy reflected from the tympanic membrane across a broad frequency range, typically 200 to 6000 Hz. Thus, WPR has the potential to reveal more information regarding the effects of AR activation on sound passing through the middle ear. The purpose of this study was to determine if acoustic reflexes can be measured ipsilaterally (IPSI) by WPR using a novel protocol. Pure tone or broadband noise stimuli typically used for IPSI reflex recording could not be employed when measuring the reflex via WPR. This is because the levels needed to activate the AR for pure tone stimuli are much higher (85-100 dB SPL) than the chirp stimulus (62 dB SPL) and would thus contaminate the reflectance measure. Therefore, we used the WPR chirp stimulus as both the probe stimulus and reflex elicitor for our IPSI reflex measures. Ipsilateral AR thresholds measured using the wideband chirp stimulus were comparable to conventionally measured IPSI ARs. Our study demonstrates the potential of wideband power reflectance as a measure of the ipsilateral acoustic reflex using the chirp stimulus as both the probe and the elicitor.