Decreased bone conduction in an audiogram indicates:
Bone conduction is a measure of cochlear function. This is tested either by Schwabach test or absolute bone conduction test or audiometrically by placing the vibrator on the mastoid bone. Decreased bone conduction or loss of it indicates hypoactive or non-functioning cochlea. All other conditions listed in (a), (b) and (c) cause conductive hearing loss with cochlear function remaining normal.
Tympanic membrane perforation
Ossicular dislocation
Ossicular fixation
Damage to cochlea
Ear