Physics Earbud Dissection Lab

Summary of my dissection analysis: When we connect an earbud/headphone jack to a computer, the computer sends electric current through the copper wire into the solenoid that is wrapped around a small magnet. Pulses of current through the solenoid produces a magnetic field that attracts and repulses the magnet continuously. This back and forth movement oscillates the plastic film and the air around it creating sound.

Further questions I’m pondering over:

Why is the plastic film connected to the solenoid directly rather than just the surround metal casing. The dissection revealed where the copper wire connected to, but where does the green wire lead? It seems to have disappeared behind the magnet that I was unable to remove. Why is the second metal casing layer with a bunch of holes in addition to the center one needed? It is only for the sake of protection and letting some air in to vibrate or is there something more?