Audiology: Assessment and Diagnosis
This domain tests the selection, administration, and interpretation of audiologic tests across ages. Expect case-based items on pure-tone audiometry, masking, speech testing, immittance, otoacoustic emissions, and auditory evoked potentials.
Core rules
- Pure-tone audiometry establishes degree, type, and configuration. Conductive loss shows an air–bone gap greater than 10 dB with bone thresholds in the normal-to-mild range; sensorineural loss shows no gap; mixed loss shows both.
- Mask air conduction when the test-ear air threshold minus interaural attenuation is at least the non-test-ear bone threshold. Supra-aural headphones give about 40 dB attenuation; inserts about 55–60 dB; bone conduction about 0 dB.
- Immittance: type A normal; type B with normal canal volume suggests effusion; type C negative pressure; absent reflexes suggest middle-ear or retrocochlear involvement depending on the pattern.
- OAEs reflect outer hair cell function; ABR estimates auditory pathway integrity and is not a direct measure of hearing threshold.
Worked example
Right ear: air 50 dB HL, bone 10 dB HL. Left ear: air 15 dB HL, bone 10 dB HL. There is a 40 dB right air–bone gap, so the loss is conductive. For right air at 50 dB with supra-aural phones, 50 minus 40 equals 10 dB, which equals left bone; mask the left ear. Tympanometry type B with normal volume and absent reflexes supports middle-ear effusion. Reasoning: masking prevents the non-test ear from detecting the stimulus; the gap defines conductive involvement.
Traps
Do not skip masking and create a false shadow curve. Do not diagnose low-frequency loss from vibrotactile responses. Do not interpret a collapsed ear canal as a real conductive loss. Do not use ABR alone to rule out mild hearing loss.