Here is a salt vibration YouTube video: https://youtu.be/wvJAgrUBF4w

What are your observations about the pitch/note of the sound needed to make the salt "dance" (plate vibrate). What happens just before and after the sound? Explain how sound travels when the Hz is increased?

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?