The perception of sound in one or both ears or in the head when no external sound is present is:

A. Otosclerosis is a condition involving abnormal bone growth in the middle ear, causing conductive hearing loss, but it does not cause phantom sound perception. B. Conductive hearing loss results from problems transmitting sound waves through the outer or middle ear, but does not explain hearing sound when none is present. C. Tinnitus is the correct answer—it is the perception of sound (e.g., ringing, buzzing, hissing) in the absence of an external source. It can be constant or intermittent and may occur in one or both ears or inside the head. D. Presbycusis is age-related sensorineural hearing loss, typically affecting high-frequency sounds, but it is not defined by phantom sound perception.