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What does an air-bone gap on an audiogram indicate?

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An air-bone gap on an audiogram indicates the presence of conductive hearing loss.1

This gap represents a significant difference between air-conduction and bone-conduction hearing thresholds, signifying a problem with the transmission of sound through the outer or middle ear. Because bone-conduction testing bypasses the outer and middle ear to stimulate the cochlea directly, a normal bone-conduction threshold alongside a poor air-conduction threshold confirms that the impairment is located in the conduction mechanism rather than the inner ear.12

In clinical practice, the size of this gap serves as a measure of the loss in transmission across the middle ear and helps determine the maximum potential improvement that could be achieved through corrective surgery. Conversely, in cases of sensorineural impairment, where the defect is located in the inner ear, the air-bone gap is typically close to zero because both air and bone conduction thresholds are affected equally.21