Wideband acoustic reflex growth function: Normative study and comparison with conventional single-frequency acoustic reflex growth function
The acoustic reflex growth function (ARGF) tested with single-frequency probe signals has been utilized as a noninvasive, objective measure in evaluating integrity of the auditory nervous system at the brainstem level. Wideband acoustic reflex (AR) procedure has shown advantages over single-frequency AR procedure. No study has systematically investigated the wideband ARGF. The objectives of this study were: (1) to characterize wideband ARGFs, which were quantified in energy absorbance change (EA ARGF) at three probe frequencies (397, 630, and 1000 Hz) and in relative AR-Level (AR-Level ARGF) for low- and high-frequency passbands for five activators, (2) to evaluate the test-retest reliability of wideband ARGFs, and (3) to compare the wideband ARGF to single-frequency ARGFs for five activators. The slope of EA ARGF at 630 Hz was the steepest among three probe frequencies. The slope of EA ARGF for 2000 Hz activator was the steepest among five activators. Low-frequency passband provided steeper slope of AR-Level ARGF than high-frequency passband. The slope of low-frequency AR-Level ARGF was the shallowest for BBN activator. The low-frequency passband provided ARGF with the smallest variability in all measures. The immediate test-retest reliability of wideband ARGF was excellent. The descriptive statistics of wideband and singlefrequency ARGF slope was performed. The dynamic range of wideband ARGF was wider (10 to 20 dB) than that of single-frequency ARGF. The slope of 630-Hz EA ARGF with less variability was significantly steeper than that of 678-Hz single-frequency ARGF for five activators. The present study demonstrates that the 630-Hz probe frequencies and low-frequency passband is more appropriate for testing wideband ARGF. The wideband ARGF might have greater potential in clinical application than single-frequency ARGF, for example, it could provide more precise comparison of the individual’s wideband ARGF with normative data.
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