When you pour a glass of water, why does the pitch of the sound of the water going into the glass get higher?
In: Physics
Sound is made of waves. You can picture it like if you tie an end of a rope to a wall, and hold the other, waving it up and down. The faster you do that, the higher the frequency (which means the pitch is higher. No matter what, the side that’s tied to the wall is a node (a point that doesn’t move) and the side you’re waving is the antinode (a point which moves the full distance from top to bottom). The same happens in a tube, like a glass of water. Now, whichever frequency takes the least energy and fits like that will be the pitch you hear. As you fill up the glass, it’s like you’re holding the rope at a point closer and closer to the wall, so the frequency has to be higher, and that’s why the pitch you hear changes.
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