mshilarious
Banned
The molecules are vibrating back and forth, but it is a very small amount.
Actually we can calculate this:
Particle displacement - Wikipedia, the free encyclopedia
But we don't need to because you already proved to yourself that air must move based on your candle experiment. What you are experiencing is air movement combined with some cognitive dissonance.
We know that air must move when a drum is struck; the deflection of the top head is a few mm; the bottom head must therefore move somewhat less (due to the small port on the side of the drum, and also the acoustic impedance of the air inside the drum). When the bottom head moves, we know all of those molecules that were resting near the reso head have to get the F out da way because the head now occupies the space where they were living. And once they start moving they ain't gonna stop right away due to inertia, until surrounding air molecules absorb their energy. As the wave spreads the number of affected air molecules will increase, this is accounted for in the formula that tells us that sound pressure in free air will drop with the square of distance.
This is why if you put your head next to the reso head your eardrum will burst, but if you are a few feet away the air motion (and therefore sound pressure) is low enough for your ear to survive.
Note how in the formula for particle displacement that it increases with decreasing frequency (the 1/w term) and increases with increasing sound pressure (Pa), exactly what we would expect from our experience.