How does the Weber test help diagnose hearing loss?

A Weber test reveals whether your hearing is stronger in one ear than in the other. The doctor first makes the tuning fork vibrate by striking it against a hard surface, then holds the stem of the fork against the center of your forehead. The vibrations are transmitted through the bone directly to the inner ear to produce audible sound. The doctor will ask you to identify the ear in which the vibrations sound louder. If you can't hear a difference, both ears have roughly equal hearing capacity. But if the sound is louder in one ear, that can mean one of two things. There may be conductive hearing loss in the ear where the sound is louder, because the vibrations are bypassing an obstruction in the middle ear. (The reason that the tuning fork sound would be louder in the obstructed ear is that it would not have to compete for attention with ambient sounds, which would have trouble passing through a middle ear obstruction.) Or there may be sensorineural or permanent hearing loss in the other ear, caused by damage to the cochlea, hair cells, or auditory nerve in the ear where the sound is fainter, because the nerves can't respond to the vibrations.