Do we need the outer ears?

As you might already know, most of the machinery that helps us hear sounds is inside our heads (called inner ear) and is not visible externally. People who lose their outer ear do not lose the ability to hear. 

Human outer ear
So the obvious question. Why do we even have these cartilage appendages on either side of the head. If at all they look like they are going to block the sounds coming from behind us!

Turns out there is a good reason why we have external ears (also called pinna). The external ear is this carefully designed sound booster that gathers the sound waves that fall on it and focuses them onto the ear drum via the ear canal. One can imagine what would happen if we were to not have outer ears and just had a hole. The sound waves would pass right by us without ever reaching the inner ear (except for those sounds that come from the sides and thus manage to reach the inner ear).

Studies have shown that the outer ear is a sophisticated piece custom made for humans. For the uninitiated, humans can only hear frequencies in the ranges between 20 Hz - 20 kHz. Of this, almost all of human speech falls in the range of 2 kHz to 4 kHz and turns out, our outer ears are especially good at amplifying sounds in this range. They can selectively boost the frequencies in this range up to 100 times and not boost other frequencies so much before sending them down the ear canal. Kind of like natural noise cancellation technology.

So there you go. Now you know the outer ears are not just girls to tuck their hair in but has a bigger nobler purpose. 

One sad thing though is that humans are among the few animals that can't voluntarily move their outer ears. Most other animals can move their outer ears to focus on the sounds from whichever direction they want to listen to. However with practice it is possible for humans as well to move their ears a little bit though. Can you move yours?


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