Tests For Hearing
Impedance audiometry is done using frequency probe of: (DNB June2011)
1. It is an objective test for hearinq?
2. It is very useful in children for assessing the hearing loss. Q
3. It consists of:
Acoustic reflex measurement
Principle: It is based on the amount of sound reflected back from the tympanic membrane when an 85dB sound pressure level (SPL) low frequency (220 Hz)Q probe tone is introduced into the sealed ear canal, and pressure in the canal is varieD. By changing the pressures in the sealed auditory canal and then measuring the reflected sound energy, it is possible to find the compliance or stiffness of the tympano-ossicular system and thus find the healthy or diseased status of the middle ear
Discussed in detail earlier
Impendance audiometry is used for diagnosing middle ear pathology .
• Various types oftympanograms are discussed in next question.
• For infants and neonates, tympanograms obtained using a 220 Hz probe may erroneously appear normal.
:. a higher frequency probe tone (660 or 1000 Hz) must be used - (Current Otolaryngology 2nd/ed p 601)