What commonly indicates a significant air-bone gap?

A significant air-bone gap is effectively represented by a difference of 15 dB or greater between air conduction (AC) and bone conduction (BC) thresholds. This concept stems from the understanding of how different types of hearing loss are classified.

When the air conduction threshold is significantly poorer than the bone conduction threshold, it indicates that there is an issue in the outer or middle ear which is interfering with sound transmission to the inner ear. This is often classified as a conductive hearing loss. In contrast, when BC thresholds are relatively normal, it suggests that the inner ear mechanisms are functional, reinforcing the idea that the problem lies in the conductive pathway.

The other options relate to hearing loss degrees or ranges, but the specific threshold of an air-bone gap is crucial in diagnosing the type and severity of hearing loss. Thus, a gap of 15 dB or more is a widely recognized criterion for indicating a significant conductive issue, making this answer the most accurate reflection of the situation.