Which of the following describes conductive hearing loss on an audiogram?

• A. AC: abnormal; BC: abnormal; No air-bone gap
• B. AC: normal; BC: abnormal; Air-bone gap present
• C. AC: abnormal; BC: normal; No air-bone gap
• D. AC: abnormal; BC: normal; Air-bone gap present

Answer: (D)

Conductive loss shows up on an audiogram as abnormal air-conduction thresholds with normal bone-conduction thresholds, plus a noticeable air-bone gap between AC and BC. This happens because the outer or middle ear problem dampens sound before it reaches the inner ear, so bone conduction (which bypasses the outer/middle ear) stays normal. In this case, the pattern that fits is AC is abnormal, BC is normal, and an air-bone gap is present. If bone conduction were also abnormal or there were no gap, the pattern would point to a sensorineural or mixed loss rather than purely conductive.