Most of what I see with the aluminum file and paper plate is not a workable design for processing an electrical audio signal It might work as a resonator to improve the sound of a tiny speaker that is processing an electrical signalThe attached link shows how to make a working speakerFrom this you should see that there is an interaction between a permanent magnet field and the electro magnetic field generated by the audio signal THe interaction between the two fields creates movement which is applied to the diapram or speaker cone to move air which inturn generates the sound waves
