Audiograms

An audiogram is a graph produced from pure-tone audiometry that records an individual’s hearing thresholds across frequencies, typically from 250 Hz to 8000 Hz, for each ear. It usually includes both air-conduction thresholds and bone-conduction thresholds, which help distinguish between conductive and sensorineural hearing loss. Thresholds are expressed in decibels hearing level (dB HL).

In a typical graph, the horizontal axis represents frequency and the vertical axis shows sound level in dB HL, with lower values at the top indicating softer sounds and higher values indicating louder sounds. Standard plots often use color-coded and symbol-coded marks to differentiate ears and testing methods: the right ear is commonly shown with red markers and the left ear with blue markers for air-conduction data, while bone-conduction data use complementary markers. The graph may also incorporate annotations from speech audiometry or other tests.

Reading an audiogram involves assessing the shape and level of the thresholds. Normal hearing is generally defined as 0 to 25 dB HL. Hearing loss is categorized by degree: mild (26–40 dB), moderate (41–55 dB), moderately severe (56–70 dB), severe (71–90 dB), and profound (91–120 dB). An air-bone gap, where air-conduction thresholds are worse than bone-conduction thresholds by more than about 15 dB, indicates a conductive component to the hearing loss; a loss where both air and bone thresholds are elevated suggests sensorineural loss.

Applications include diagnosing the type and extent of hearing loss, guiding treatment plans, fitting hearing aids or cochlear implants, and monitoring changes over time. Limitations include the exam’s focus on quiet, controlled tones, which may not reflect real-world listening in noise or with complex signals.