Simultaneous measurement of auditory-steady-state responses and otoacoustic emissions to estimate peripheral compression
Assessment of the compressive nonlinearity in the hearing system provides useful information about the inner ear. Auditory-steady state responses (ASSR) have recently been used to estimate the state of the compressive nonlinearity in the peripheral auditory system. Since it is commonly assumed that outer hair cells in the inner ear play an important role in the compressive nonlinearity, it is desirable to selectively obtain information about the inner ear. In the current study, the signal in the ear canal present during ASSR measurements is utilized to extract sinusoidally-amplitude modulated otoacoustic emissions (SAMOAEs). It is hypothesized that the stimulus used to evoke ASSRs will cause acoustic energy to be reflected back from the inner ear into the ear canal, where it can be picked up as an otoacoustic emission (OAE) and provide information about cochlear processing. Results indicate that SAMOAEs can be extracted while measuring ASSRs using sinusoidally amplitude modulated tones. However, comparison of simulations using a transmission model and the data show that the SAMOAE measured above 50 dB SPL are strongly influenced by the system distortion. A robust extraction and evaluation of SAMOAE in connection with ASSR may be possible by a proposed method to minimize the distortion. The ability to evaluate SAMOAE over a large input level range during ASSR measurement will provide information about the state of the peripheral auditory system without the need of additional measurement time.
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