A Reader asks why, during ear impression taking, she can still hear conversation.

Question:

When ear impressions were being made on me at my dispenser's office I could still hear him and my husband in conversion as if my ears were not even plugged. I was surprised, because both ears were filled with material all the way to the eardrums. How is that possible? ---Mrs. E.S.

Answer:

Dear Mrs. E.S.: I'm glad you asked that, for it provides a lesson in ear physiology that I think will be interesting to our readers.

There are actually four avenues of hearing to our ears. The first two everyone knows about: sound traveling from the external ear to the middle ear ossicles to the inner ear on up the central auditory process (CAP) and auditory cortex in the higher brain region. Since these two pathways (right and left) were closed off with impression material, the only other routes would have been:

• Through bone conduction, in which the body's skeletal frame can act as a conduit of sound, to the inner ear.
• But most likely you were hearing through the nose and mouth through a patent (open) Eustachian tube directly into the middle ear cavity and from there through the oval and/or round windows leading into the cochlea (inner ear).

It is surprising how much sound travels these two routes, without which one could not monitor the sound of their own voice properly.

Once, when I was a visiting consultant at an audiology clinic, a staff audiologist came in just as we were making ear impressions on a new hearing aid patient. He proceeded to give me some sensitive health information about another patient in front of this patient, to which I suggested we talk later about it.

His comment was, "He can't hear what I'm saying. His ears are plugged up" to which the patient said, "Oh yes I can!" Shock to all, the patient was hearing through his open mouth, up an otherwise normally closed Eustachian tube into the middle ear cavity.

Moral to the story is, yes, there is more than one road leading to Rome:er, the brain, where hearing actually occurs.