Audiology and Hearing
Audiology and Hearing tests hearing science, disorders, assessment, amplification, and rehabilitation. Expect audiogram interpretation, tympanometry, screening, and candidacy questions rather than equipment repair.
Core rules
- dB HL is the reference for audiometric thresholds; dB SPL is physical sound pressure. Do not compare them directly.
- Degree is often classified from the pure-tone average (PTA) at 500, 1000, and 2000 Hz: normal -10 to 15, slight 16-25, mild 26-40, moderate 41-55, moderately severe 56-70, severe 71-90, profound 91+ dB HL.
- Conductive loss: air thresholds elevated, bone normal, air-bone gap >10 dB. Sensorineural: air and bone elevated together. Mixed: bone elevated plus an air-bone gap.
- Type B tympanogram is flat and may reflect middle-ear effusion, perforation, or occlusion; type C shows negative middle-ear pressure, often eustachian tube dysfunction.
- OAEs suggest healthy outer hair cells and are absent with significant sensorineural loss; ABR estimates hearing in difficult-to-test populations but is not a substitute for behavioral thresholds when those are reliable.
- Hearing aid verification uses real-ear measures; cochlear implantation is considered for severe-to-profound sensorineural loss with limited amplification benefit.
Worked example
An audiogram shows air thresholds of 60 dB HL at 500, 1000, and 2000 Hz; bone thresholds are 20 dB HL at the same frequencies. PTA is 60 dB HL, a moderate loss. The air-bone gap is 40 dB, and bone thresholds are mildly elevated, so the diagnosis is mixed hearing loss, not a purely conductive loss.
Traps
- Calling a 15 dB threshold mild loss-it is normal.
- Ignoring masking when air-bone gaps appear.
- Using tympanometry alone to diagnose otitis media.
- Assuming OAEs are present in all normal-hearing adults; they can be absent with noise exposure or middle-ear dysfunction.