Hearing Health Guide
Definition
An air-bone gap is the audiometric finding where air conduction thresholds (measured through headphones) are significantly worse than bone conduction thresholds (measured via a skull vibrator) at the same frequencies. A gap of 10 dBHL or greater at a given frequency is considered clinically significant and indicates conductive hearing loss: a blockage or dysfunction in the outer or middle ear.
On an audiogram, if your air conduction thresholds (O for right, X for left) fall significantly lower than your bone conduction thresholds (plotted with brackets or carets), there is an air-bone gap. This means your cochlea is functioning relatively normally, but sound is being impeded somewhere between the opening of the ear and the inner ear.
Common causes include earwax blocking the ear canal, fluid behind the eardrum from otitis media, a perforated eardrum, otosclerosis, or problems with the ossicular chain (the three small bones of the middle ear).
An air-bone gap changes the treatment approach significantly. Conductive hearing loss (indicated by an air-bone gap) is often medically or surgically treatable, unlike most sensorineural loss. An audiologist will refer to a physician (typically an otolaryngologist/ENT) when an air-bone gap is present, particularly when the cause is not obvious.
The size of the gap matters. A large air-bone gap (30 dBHL or more) at multiple frequencies typically indicates a more significant structural problem. A small gap that resolves on follow-up testing may have been caused by temporary wax buildup or fluid from a recent cold.
Common Questions