Auditory Physiology Laboratory
Research
EEOAE
Electrically evoked otoacoustic emissions (EEOAE) can be used in addition to traditional response measures to characterize insults to the inner ear.
Hearing loss can occur as a result of loud sound exposure. At the time of the exposure it is difficult to predict, based on traditional measures of hearing sensitivity, if the hearing loss will be temporary or permanent. We are exploring the effects of alternating current (AC) stimulation of the ear to evaluate hearing before and after acoustic trauma. AC stimulation of the inner ear causes sounds that can be recorded in the ear canal. These acoustic emissions are called the electrically evoked otoacoustic emissions (EEOAE).
The figure above (Baseline) shows the "time-delay" and "frequency-delay" spectrums of the EEOAE before acoustic trauma. Short delay components occur for a broad range of frequencies while long delay (> 0.5) components show a spread across the frequency range. The figure below is the same spectrums two weeks after the loud sound exposure.
The exposure primarily alters the long delay components between 1.0 and 1.5ms in the frequency region 8.0-15kHz. AC stimulation of the inner ear is a useful tool to evaluate cochlear function and may lead to a correlation of the type of hearing loss with anatomical changes within the inner ear.
Activation of the Efferent Reflex
Activation of the efferent reflex through acoustic stimulation is a non-invasive means of assessing efferent function and cochlear activity. A focus of the lab is the efferent system and its role in hearing. The efferent system is known to modify transduction mechanisms within the inner ear. Sound stimulation activates the efferents as a part of a reflex loop.
The graph above shows the effect of acoustic activation of the efferent system and its effects on the otoacoustic emission (DPOAE) recorded in the ear canal. This figure shows a summary of the maximum efferent mediated adaptation of the DPOAE for 168 intensity combinations of the primary tones in 0.4 dB steps. Adaptation strength was defined as the DPOAE level at steady state subtracted from the DPOAE level at the onset of the primary tones.
