When you pour a glass of water, why does the pitch of the sound of the water going into the glass get higher?

Question

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

Answer 1

You know how different size drums make different notes, right? A little toy drum makes a high pitch *pang-pang*. A regular drum kit makes lower sounds, and the biggest drum in that kit (the bass drum on the floor) is the lowest. Then there’s the [huge Japanese drums](https://i.ytimg.com/vi/C7HL5wYqAbU/hqdefault.jpg) – if you’ve ever heard them, they’re seriously low and booming.

Well, the air in a glass vibrates just like the air in a drum. The fuller the glass, the smaller the air-space, the higher-pitched the “drum”.

(For one more level of detail “*why* is a smaller drum higher pitch?” Well “pitch” is the same as “frequency” aka how many times the air vibrates per second. Sound moves at a given speed, so the smaller the space it’s trapped in the faster it will be bounced back and forth between the walls aka higher frequency/pitch.)