Hearing Physiology & Audiological Tests
Distinguish conductive and sensorineural patterns and interpret basic hearing tests in context.
Quick revision ↓ Medical Dictionary
01Sound transmission
The external canal guides sound to the tympanic membrane, and the ossicles transmit vibration towards the cochlea. Hair cells convert mechanical signals into neural activity carried through the auditory pathway. Disease in the external or middle ear commonly causes conductive loss; cochlear or neural disease causes sensorineural loss. Both components may coexist as mixed hearing loss.
02Assess function and impact
Ask about speech understanding, background noise, telephone use and occupational or educational difficulty. Establish whether loss is sudden, progressive, unilateral or bilateral. Examine for wax, infection and perforation before interpreting bedside tests. Communication needs should be addressed during the encounter, with the clinician facing the patient and checking understanding rather than merely speaking more loudly.
03Tuning-fork principles
Rinne compares air with bone conduction; air conduction usually exceeds bone conduction in normal hearing and sensorineural loss. Bone conduction exceeding air conduction suggests conductive loss, but profound unilateral sensorineural loss can mislead through cross-hearing. Weber tends towards the affected ear in conductive loss and the better ear in unilateral sensorineural loss. These are screening clues, not definitive audiometry.
04Formal audiology
Pure-tone audiometry plots hearing thresholds by frequency for air and bone conduction. An air-bone gap supports a conductive component when testing is reliable. Speech testing adds functional information. Masking may be needed to isolate the tested ear. Interpret the audiogram with history, otoscopy and test quality rather than assigning a cause from the graph alone.
05Middle-ear and objective tests
Tympanometry assesses middle-ear mechanics and must be interpreted with canal volume and otoscopy. A flat trace can arise in different settings and is not a diagnosis by itself. Otoacoustic emissions and auditory brainstem testing have roles in selected patients, including children. An incomplete or unreliable test requires a follow-up plan rather than assumed normal hearing.
High-Yield Revision
- Rinne remains air-greater-than-bone in many sensorineural losses.
- An air-bone gap suggests a conductive component.
- Tympanometry needs canal-volume and clinical context.
Common Pitfalls
- Treating a tuning fork as a complete audiogram.
- Diagnosing from a flat tympanogram alone.
References & Further Reading
Read the relevant guideline sections alongside these original clinical teaching cases. Local pathways, available services and individual patient factors determine care.
Reference review: 28 September 2026. Consult current local protocols for prescribing, procedures and escalation.