Pure tone audiogram interpretation

What it is

Pure tone audiometry plots hearing level in decibels against frequency in hertz. The frequencies run from 125 to 8000 Hz and the hearing level from -10 to 120 dB HL, and the chart is divided from normal hearing ability down through mild, moderate, moderately severe, severe and profound hearing loss. Every ear and every route carries its own symbol: O for right ear air conduction and X for left ear air conduction, < and > for bone conduction on the right and on the left, with further marks for testing with masking and for no response. The test is both qualitative and quantitative, giving the type of hearing loss and its severity, and for assessment three frequencies are taken as reference points: 500 Hz, 1000 Hz and 2000 Hz. It is also the first test in tinnitus. Where the tinnitus is thought to come from the auditory system, pure tone audiometry, tympanometry and tinnitus sound matching are done, and a unilateral tinnitus takes MRI or CT to exclude retrocochlear lesions. Where a vascular cause is suspected, MRI or angiography is used instead.