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?
In: 80
It is because of superposition of waves.
Imagine the following scenario, you are on a swing and swinging, you will moving in an arc
Now you start standing and sitting while you are swinging, what kind of motion is that? Up down, an arc or mixture of both?
Now imagine that someone is rotating the swing and now you are also spinning? What are you doing? swinging, going up and down or rotating?
The answer is, you are doing a mix of all these, and this is called superposition.
Now imagine that someone is rotating the swing and now you are also spinning. What are you doing? swinging, going up and down, or rotating?
The first instrument vibrates the air from a stand-still position, the second instrument vibrates the air on top of the first’s vibration, third will vibrate the air on the resultant of first 2 instruments, and so on.
No add wind to the mix, will move all of this vibration along the wind direction.
Look up standing waves on YT.
A bunch of people have answered the direct question about how one medium can contain many frequencies of vibration, but another thing going on with your ears is that you have two of them, and they’re each hearing slightly different vibrations. If you have one sound source to your left and another to your right, their two different vibrations overlap differently in your left ear compared to your right ear.
Your brain has heard and already knows the sound of, for example, a violin or clarinet. So if you hear those two sounds at once, your brain is naturally capable of isolating them.
The one item missing here is to understand that what we perceive as “time” when it comes to sound is not how we typically think of time. When we normally think of “now”, it’s an instantaneous moment, like a single frame of a movie when you hit the pause button. At that instant, the air a sound wave (or multiple waves) is moving through has a discrete pressure at any particular location (but may be different at different locations). In the case of multiple waves, the pressure at any location reflects the sum of all the waves passing through that spot. Pressure, however, doesn’t generate sound. Sound is generated by changes in pressure, which requires some amount of time to let the waves move through. Hence the sound you here right ‘now’ is actually your brain sampling over several ‘nows’. The more time points your brain samples over, the more accurately it can make judgements about pitch (the reverse is also true). Hence a sound wave played for only a tiny fraction of a second is too short for your brain to figure out a pitch, and instead it sounds like a ‘bang’ of a drum. Play the same sound for longer and it begins to actually have a tone (or multiple tones). You needed the extra time to figure out what the sound was, but you didn’t even realize you were doing it.
So this brings us to the last part: how does a sound contain multiple sounds in it? if each single sound is a wave of a single frequency, then a combined sound is a wave of multiple frequencies. The combined sound wave excites all the neurons that detect the component frequencies over the same period of time that you heard the combined wave, and each frequency has an intensity (volume) of detection corresponding to how loud each component in the wave was.
Here’s a simple diagram: [https://puu.sh/Jo4TD/e80645943c.png](https://puu.sh/Jo4TD/e80645943c.png)
First line is how a high frequency, treble note looks like.
Second line is how a low frequency bass note looks like.
Third line is them both being heard at the same time. You can combine any number of random notes like this, you just add together the different vibrations.
Oh and if you have two vibrations that are opposite of each other, they can cancel each other out, that’s how noise canceling headphones work. [https://puu.sh/Jo4S0/49836b7f8b.png](https://puu.sh/Jo4S0/49836b7f8b.png)
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