I wonder about this.
If you pour water in a closed tank, it makes a noise. I have noticed that as the container becomes more and more full, the pitch of this noise also increases. Why is that?
I do not study, nor have any knowledge of beyond basic concepts, of the physics involved in sound and vibrations.
However, my hypothesis is that this happens because the "chamber" where the sound is produced gets progressively smaller, therefore it behaves like a flute - as you change the shape of the chamber, the sound that air makes as it passes also changes.