Rodney Lusk, M.D.
Hi, I'm Doctor Rodney Lusk, Director of the Boys Town Ear, Nose & Throat Institute.
Tympanometry is a special machine that generates a sound that bounces off the ear drum and a sensitive microphone measures how much sound comes back.
If a lot of sound bounces back then the ear drum is tight, if a little sound comes back then the ear drum has pressure close to the same on both sides, which is what we want.
By varying the pressure in the ear canal we can indirectly measure the pressure in the middle ear by how much sound is bounced back.
The normal tympanogram or type A, has a nice peak at the same pressure as it is in the ear canal or atmospheric pressure.
A flat tympanogram or type B, shows no peaks because the ear drum cannot move because of a hole in the ear drum or fluid in the middle ear. Type B tymps are associated with fluid 85-100% of the time. Extensive scarring of the ear drum may also result in a flat tymp.
A type C tympanogram is peaked in the high negative pressure. This is usually associated with Eustachian tube dysfunction but not fluid.
For more information and videos on pediatric ear, nose and throat problems please visit boystownent.org.