There is a theory, that all matter is energy in vibration in it's core. I have read a lot of articles and watched a lot of videos and documentaries about that topic and they all state, that there is basically no matter and all is vibration. What we call matter is basically the energy in the low states of vibration.
Vibration is energy. Energy is vibration.
What does vibrate then??
Sound is the vibration of the air molecules (mechanical wave of pressure and displacement, through a medium). That means, that the sound is the vibration of matter (air). If matter is also vibration, then air must be a vibration of something else (because how can vibration exist without a medium?). That means, that sound is the vibration of the vibration of something, which should also be a vibration... But what does actually vibrate?