Tympanometers

Tympanometers are diagnostic devices used in audiology and otolaryngology to evaluate middle ear function by measuring the movement of the tympanic membrane in response to changes in air pressure within the ear canal. The test yields a tympanogram, a graph of acoustic admittance or compliance as a function of ear canal pressure, and can provide static compliance, ear canal pressure, and tympanometric peak pressure values. Many devices also assess acoustic reflex thresholds.

They operate by placing a probe seal in the external ear canal. The device changes the air pressure while delivering a probe tone and uses a microphone to detect sound transmission. From these measurements it derives admittance or impedance and plots a tympanogram. The peak indicates middle-ear pressure and membrane mobility; the shape is classified (Type A, As, Ad, B, C per Jerger) to reflect normal, shallow or hypermobile membranes, flat traces due to effusion or perforation, or negative pressure.

Modern tympanometers range from compact handheld units to integrated audiology systems. Some implementations offer high-frequency tympanometry for infant ears, multi-frequency tympanometry, real-time reflex testing, and automatic interpretation. Data can be stored and linked with audiograms.

Clinical uses include assessing middle-ear effusion, Eustachian tube dysfunction, tympanic membrane perforation, ossicular chain abnormalities, and monitoring after tympanostomy or trauma. They are commonly used in pediatric screenings, routine ENT examinations, and preoperative evaluations.

Limitations include the need for an adequate ear-canal seal and patient cooperation. Cerumen, canal anomalies, and external ear pathology can affect results. Some conditions may yield normal tympanograms despite pathology; results should be interpreted with otoscopic findings and other tests.