An air-bone gap of 15 dB or greater with bone conduction in the normal range indicates which type of hearing loss, given a threshold of 55 dB HL?

• A. Mild conductive hearing loss
• B. Moderate mixed hearing loss
• C. Moderate sensorineural hearing loss
• D. Conductive hearing loss

Answer: (D)

The key idea is distinguishing conductive from sensorineural loss using an air–bone gap. When bone conduction is normal but there is an air–bone gap of 15 dB or more, the inner ear (cochlea and auditory nerve) is functioning, and the issue lies in the outer or middle ear preventing sound from being conducted properly.

Here, the air-conduction threshold is 55 dB HL, but bone conduction remains in the normal range. The gap between air and bone thresholds meets the criterion for a conductive pattern, so the loss is due to problems in the conductive pathway (outer or middle ear) rather than the inner ear. The presence of the gap excludes sensorineural or mixed losses, since a sensorineural loss would show elevated thresholds for both air and bone conduction with no such gap. Thus this pattern indicates conductive hearing loss (the degree appears moderate based on the air-conduction threshold, but the type is conductive).