Middle ear muscle reflex (MEMR) measurements have been a part of the standard clinical immittance test battery for decades as a cross-check with the behavioral audiogram and as a way to separate cochlear from retrocochlear pathologies. MEMR responses are measured in the ear canal by using a probe stimulus (e.g., single frequency or broadband noise) to monitor admittance changes elicited by a reflex-activating stimulus. In the clinical MEMR procedures, one test yields changes in a single measurement (i.e., admittance) at a single pure tone (e.g., 226 or 1000 Hz). In contrast, for the wideband acoustic immittance (WAI) procedure, one test yields information about multiple measurements (e.g., admittance, power reflectance, absorbance) across a wide frequency range (e.g., 250 to 8000 Hz analysis bandwidth of the probe). One benefit of the WAI method is that the MEMR can be identified in a single test regardless of the frequency at which the maximum shift in the immittance measurement occurs; this is beneficial because maximal shifts in immittance vary as a function of age and other factors. Another benefit is that the wideband response analysis yields lower MEMR thresholds than with the clinical procedures. Lower MEMR thresholds would allow for MEMR decay tests in ears in which the activator levels could not be safely presented. Finally, the WAI procedures can be automated with objective identification of the MEMR, which would allow for use in newborn and other screening programs in which the tests are completed by nonaudiological personnel.
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