>>12048068yes, resonance and harmonics, one interesting thing that a lot of the people that are into this do NOT know is that the main reason this pattern forms is because the surface used goes into "breakup", this term is used in sound engineering this is a condition where a louidspeaker's cone can't handle the inertia and literally "breaks" creating harmonics, the cone's surface can not follow the original signal (its too heavy or doesn't have enough rigidity) and creates regions that vibrates on their own resonance, is basically "harmonic distorsion", the cool thing is that this patterns are very beautiful
this is how a cone should act (it follows the movement of the center "voicecoil")
https://www.youtube.com/watch?v=PfkOVB6owwkthis is under "breakup"
https://www.youtube.com/watch?v=ZRdieN8xTxMhttps://www.youtube.com/watch?v=Q3oItpVa9fs 
