Which constitutes a significant air-bone gap?

• A. A gap of 15 dB or more at 250, 4000, or 8000 Hz
• B. A gap of 15 dB or more at 500, 1000, or 2000 Hz
• C. A gap of 15 dB or more at 125, 250, or 500 Hz
• D. No gap

Answer: (B)

A significant air-bone gap is identified when there’s a 15 dB or greater difference between air-conduction and bone-conduction thresholds at frequencies that matter most for speech. The standard mid-frequency range used to judge this is 500, 1000, and 2000 Hz. If a 15 dB or greater gap appears at any of those frequencies, it indicates a conductive component (outer or middle ear involvement) rather than purely sensorineural inner-ear loss. That’s why the option listing 500, 1000, or 2000 Hz fits the common clinical criterion for a significant ABG.

Low-frequency (125–500 Hz) or high-frequency (4000–8000 Hz) gaps are not typically used to define a significant ABG because measurements at those extremes are less reliable and don’t align with the speech-range focus used in routine audiometry and diagnostic decision-making. If there’s no gap, obviously there isn’t a significant ABG.