How many ears do you have?

• It seems like a strange question, to ask, "How many ears do we have?" and yet there are many misconceptions about the ear. For example, we have already discussed how we don't hear with our ears.

• The ear, as wonderful as it is, is simply a transducer--a mechanism that changes the form of energy in a message. In the case of hearing, mechanical sound waves are converted into electro-chemical impulses.

• So let's begin this section with a short pop quiz. Let's see how you do? Here is the multiple choice question:

• How many ears do you have?

• a. One

• b. Two

• c. Three

• d. Four

• e. Five

• f. None of the above.

NOTES: See a more technical review of the ear.

WARNING--The Illustrations presented below are not to be taken as scientific replications.

• Below are some sketches of possible ear configurations relative to the quiz on the above. If you use them as a citation, don't forget to include the "Twighlight Zone reference"

An ear by any other name will hear differently

• Of course, the answer was none of the above. Semantically we have SIX ears!
  
  
  
  They include two Outer Ears; two Middle ears; and two Inner ears.

• Admittedly it was a bad question, and there were misleading drawings; but that's what I'm paid for.

• Of course, pragmatically we have two ears, each broken up into three sections which we call the Outer, Middle and Inner ears. But why bother with all this nomenclature at all? It is because they each contribute differently to the hearing process.

• Let's take a look at each segment of the ear individually, and see what the boundaries are and what contribution is to hearng.

The Pinna is the most visible parts of the (Outer) Ear

• The Outer Ear: The Pinna of the Outer ear is the most visible part. It's what many folks think of as the ear. In terms of hearing, it doesn't really contribute much.

• If we had Pinnas like rabbits or donkeys there might be some sound gathering and resonance benefits.

• Below, you can see Diagram from our Text of the Outer Ear.

The most critical part of the Outer Ear is the External Auditory Meatus.

• But then try to imagine Tom Cruise with rabbit or donkey ears and the spell might be diminished a bit (my wife denies this, of course). As it is, the Pinna is suitable for piercing purposes, hanging earrings and perching glasses on. Some boxers also like to bite it.

• Somewhat centered in the Pinna is the ear canal. That is what we called it in CD 261; but this a 300 level course so it is now referred to as the External Auditory Meatus.

• There is a quaint line I once heard in a Humphrey Bogart movie (I think) that goes like, "Breath in my External Auditory Meatus one more time and you'll get five extra ossicles in yours." And then again it may have been a Bugs Bunny cartoon.

A Conductive Hearing Loss can occur if the External Auditory Meatus is obstructed.

• The External Auditory Meatus functions clearly as a passageway to conduct air (sound) waves into the middle ear. Anything that interferes with this canal will hamper the hearing process.

• I see students in class putting their fingers in both ears quite frequently during parts of the lecture. The result for them is a reduction of the loudness of sound. This is referred to as a Conductive Hearing Loss. There are three interesting facts about a conductive hearing loss.

• (1) It is impossible to be deaf with a conductive hearing loss. The most you could hope for under any circumstance is a 60 dB loss.

• Hence, if I put my mouth right next to a person with their fingers in their ears and talk reasonably loud (over 60 dB), they will still hear every word of the lecture.

• Not only will they hear it all but the (2) fidelity will be normal. That is, there will be no distortion of my somewhat high shrill nasal voice.

Wax impacted in the External Auditory Meatus can cause a Conductive Hearing loss

• Another fact about a Conductive loss is that it is usually (3) remediable by medical and/or other means, i.e., hearing can be recovered. If I tickle a student under the armpits, they will remove their fingers from their ears and hear normally.

• Wax accumulation in the External Auditory Meatus can can be another common cause of a Conductive loss. Basically, wax is exuded by special cells in the ear canal as a means of cleansing the ear.

• Dust particles, or parts of hapless insects if they have wandered in there, are embedded in the wax and are removed when the wax falls out.

• Some times the wax doesn't fall out and becomes impacted in the canal. If it occurs in both ears we can get a significant loss that can interfere with communication and social interaction.

If children put objects in their ears, they can get a conductive hearing loss that can last a long time.

• With a conductive hearing loss, you may find listening laborious; you may find yourself asking people to repeat a lot; and you may get the unpleasant feeling of being an "outsider" in a social group, if not the "butt" of unkind social remarks.

• The good news, of course, is that the wax can be removed, and when it is, hearing is as clear as it was before. What may have been gained is a new awareness of how wonderful and important this transducer is!

• In a more worrisome vain, show me a two year old, and I will show you a person who has a life's goal to find and place objects in very body orifice. If it happens to be something like beans in the ears, we can get a significant hearing loss.

• The problem here is that objects in the canal may not be easily noticed because of the zig zag shape of the canal. Nor would the child typically be able to verbalize what had happened.
  
  Let's move on now and examine the Middle Ear to see how and why it actually makes sounds louder.