AC-BC gap

AC-BC Gap

A normal finding in pure tone audiometry, in which the threshold for hearing sounds conducted through the air—air conduction (AC)—is lower than the threshold for sounds conducted through the bones of the skull—bone conduction (BC). The relationship changes dramatically in conductive hearing loss, in which the threshold for BC is lower than that for AC.
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AC-BC gap

Audiology A normal finding in pure tone audiometry, in which the threshold for hearing sounds conducted through the air–air conduction, AC is lower than the threshold for sounds conducted through the bones of the skull–bone conduction, BC; the relationship changes dramatically in conductive hearing loss, where the threshold for BC is lower than that for AC. See Pure tone audiometry.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.