Like for example when I’m listening to an orchestra I can hear a clarinet and a violin quite distinctly from one another, but they’re both sounds vibrating through the same air. Logically, shouldn’t one air only be able to carry one frequency (Vibrate in only one way)? How does the air contain so many frequencies simultaneously?
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So waves (including sound waves) are pretty complicated and pretty cool.
First thing to mention: resonant frequencies. Have you ever been walking with a cup of water, and even though you’re not walking super fast, the water just starts sloshing really bad and spills out? That’s because your walking speed happened to hit the resonant frequency of the water.
Some things like to vibrate at certain frequencies. Imagine pushing a kid on a swing. If you push at random times, that kid isn’t going anywhere. But if you push at just the right time, in the right rhythm, that kid swings higher and higher, right? When you slosh the water, you accidentally walked at just the right speed and “pushed the kid on the swing” at just the right time, making the water slosh higher and higher.
So that’s the first part. Next thing is waves.
That kid on a swing basically represents the simplest kind of wave. They go up and down at an even, constant rhythm. Up, down, up, down, always the same time (in a perfect, hypothetical world, for the sake of this example).
The cool thing about simple waves is, they add together to make complicated waves. So you take a wave at 4 Hz (that’s 4 up and downs per second) and add it to a 3 Hz wave and a 5 Hz wave and you get an even more complicated wave.
And the coolest thing is, you can take that complicated wave and separate it back out into the simple waves! That works by the resonant frequencies mentioned above. Imagine you were pushing the kid on a swing with some complicated pattern, but among the seemingly random pushes, some of the pushes are just the right timing to make the kid swing higher. Even though your push pattern is super complicated, when we see the kid starts swinging higher, we know that somewhere in that pattern is the perfect swing frequency.
Your ear contains tons of swings of different sizes that respond to different rhythms (frequencies). A sound wave (that complicated swing pushing pattern) passes through all those swings, and *some* of them start swinging. So your brain knows that in that super complicated pattern, there was actually *this* frequency and *that* frequency.
And your brain has a big database of different frequency patterns and what those mean. So that’s why you can hear violins and trombones and drums in just the vibration of air.
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