record observations about the size of the bowl and the pitch/note of the sound needed to make the salt "dance" (bowl vibrate). What happens just before and after the sound? Explain how sound travels?

Concerning the different patterns in the salt, what do the areas where the salt has not collected tell you about the movement of sound? What do the areas where salt has collected tell you? (Use technical terms).

https://youtu.be/aQNuP7vNn3k?feature=shared