Why are our ears shaped the way they are with all their weird ridges? Why aren’t they more simply shaped like a funnel?
In: Biology
This video goes into some neat details about our awesome ears…
This actually has to do with sound localization– our ears being shaped weirdly enables us to be better at determining where in our three-dimensional world a sound is coming from.
The two primary ways that enable an individual to localize sounds in space are sound arriving at your ears at slightly different times, and at slightly different levels of intensity. I won’t go into the gory details here, but if you want a full rundown of sound localization, I encourage you to refer to [this](https://www.reddit.com/r/explainlikeimfive/comments/dtgkp3/eli5_how_do_we_percieve_the_direction_in_which_a/f6wnun6/)
But anyways, given that we mainly perceive sound through differences in time and intensity of the sound reaching our ears, that leads to a bit of a problem.
There’s this concept called a “cone of confusion.” Imagine a clock around your head, with 12 o’clock directly in front of you, and 6 o’clock behind you.
Imagine a tone at 10 o’clock, and a tone at 8 o’clock. The difference in time and intensity these sounds will reach your ears at will be identical, so theoretically you wouldn’t be able to distinguish where a sound was coming from– in front of or behind you. In fact, if you imagine a sound at 10 o’clock, you can move that sound up or down in an arc and it would suffer from the same problems. In this way, there is a sort of “cone” where any sounds within the cone have the same time difference and level difference, and you’ll be able to localize them in space (hopefully you see what I’m talking about here). This is called the cone of confusion, and it’s a real thing. You have infinitely many cones of confusion all nested within one another, and any 2 sounds that are in the same cone of confusion are hypothetically unable to be distinguished from each other.
Confused? Hopefully this image helps clarify–[this](https://www.researchgate.net/profile/Bill_Kapralos/publication/257764036/figure/fig2/AS:297648201453572@1447976269745/Cone-of-confusion-A-sound-source-positioned-on-any-point-on-the-surface-of-the-cone-of.png)
Luckily, we have mechanisms to deal with sounds lying within the same cone of confusion. The easiest way to deal with it is just to move your head a little bit. However, another “trick” your body has to deal with cones of confusion is that sounds are funneled into your ear differently depending on where the sound is in space.
The outer, squishy, cartilage bit you’re talking about in your question is called the pinna of the ear. Everyone’s pinna is shaped differently, and so funnels sound differently into the ear depending on where it is If I play a sound and move it around your head, you’ll perceive the sound as changing in loudness, even if its the same absolute distance from your head. This is because your ears and upper body will filter the *same* sound differently depending on where in space it is.
What do I mean by this? Imagine you’re in a room with absolutely no sounds except magical speakers floating around. Imagine that I put a microphone into your ear, right next to your ear drum. Imagine one of these speakers floats somewhere on your left side, slightly above your head. I get this speaker to play sounds of different frequencies at the same loudness. The microphone inside your ear canal actually won’t record the same intensity for all the different frequencies– at any point in space, different frequencies are “better” at making it to your ear. This is called the directional transfer function, or DTF
This is another “trick” your brain uses to help localize sounds– you subconsciously know your unique DTF, and you can use it to judge where sounds are.
Part of the shape is to allow the ear to efficiently collect sound waves. However, part of it is also to disrupt the collection – allowing the angle of sound to have a greater effect on what you hear, allowing you to use your ears to sense the direction sound is coming from.
Other shapes are there to keep water from pooling into your ears (from sweat) and to drain efficiently at the same time. Plus, the shape needs to be strong enough to not easily be damaged (heat, cold, fights etc) yet not be a massive resource drain to build them. Additionally, the shape has to be formed by evolution – so each bump and twist and turn has to come about by random mutations that happen to work better for one thing, but maybe worse for another.
Ears not only have to funnel sound into the ear, but their shape helps us determine from which direction the sound came. If they were perfect conical shaped funnels we’d have no way to determine if the sound came from in front of us or behind us, we’d only be able to determine if it were more on our left or our right.
By shaping the sound as it comes into the ear, its timbre changes and our brain can interpret the quality of the sound and translate it into positional information.
Of course they weren’t DESIGNED like this, but more that those organisms with odd shaped ears were able to better discern where threats were coming from and survive and pass on their weird shaped ears gene.
Cause if it was a plain funnel you couldn‘t distinguish noises from up or down, neither front or back
Sounds bounce off of things and the weird curves and shapes actually help you know what direction the noise came from.
It lets us know if noises are above or below us. Put some playdough on yours ear bumps to smooth them out. Close your eyes. Have someone clap — point at them. Record with video.
[https://youtu.be/Oai7HUqncAA?t=256](https://youtu.be/Oai7HUqncAA?t=256)
[Smarter Every Day](https://youtu.be/Oai7HUqncAA?t=344) youtube channel did a bit on this. They even put clay in parts of the ear, and the subject was no longer able to tell which direction the sound was coming from
If it were shaped like a funnel, then we would have a very narrow sound stage and barely any spatial knowledge of the sounds we hear. The funnel reverberates the sound before it reaches the bottom end of the funnel so almost all the spatial information is lost there. This would make it harder for us to survive. Here are the key factors determining the shape:
1. The outermost fold is called the pinna and has special resonance properties that reverberates the high frequency sound into the ear canal without losing the spatial information this helping us to locate high pitch noise easily.
2. The pinna is the most important fold to determine the location of the sound source. Here is a fun experiment showing why that is
https://www.scientificamerican.com/article/ears-do-their-design-size-and-shape-matter/
3. The ear canal enhances sounds of a different frequency range. I’m guessing it’s mostly mid to low pitch based on its hollow cylindrical shape. Correct me if I’m wrong.
4. And since sound is a mechanical vibration, the ear needs to be strong enough to resist minor pressure fluctuations. The soft bones in the ear assist with that.
Think of the outer ear as a conditioning filter which filters and conditions the incoming (Raw) sound and provides a compatible output for the the middle and inner to function properly.
I’m sure there’s more to it that I’m not aware of yet. Enlighten me.
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