We have seen how radio waves are generated. It is possible to embed information on radio waves such as sound, image or data in order to transfer these in long distances. Let us take the example of sound. First of all we need to capture sound. But what is sound exactly? How do we make a sound? For instance let us hit a drum. The membrane of the drum will be set in motion, in a vibratory manner. The vibrations of the molecules of the drum will cause vibrations of the molecule of the air they are close to and these will transfer the vibration to their neighbours. Eventually the vibrations reach the air molecules that are inside our ears and these will transfer the vibrations on our ear drum. This mechanical signal will be captured by the receptors of our nervous system and will be transformed to an electric one to be subsequently processed by the brain.
How do we capture sound? By using a microphone. What does a microphone do? It transforms sound to an electric signal. How could we link sound to electric signal or electricity generation?
How can we generate electricity given what has been presented on this site?
According to the law of Faraday, when we move the magnet towards the coil, electricity is generated on the coil. This happens because there is a change in magnetic flux, represented by the magnetic field lines.
Now, we want sound to generate electricity. What is sound? Air vibrations. Meaning air moving back and forth. Could we make air move the magnet? How? By attaching a drum or a membrane on the magnet. For practical reasons, we attach a membrane on the coil. We immobilise the magnet and we allow the coil to move towards the magnet. When vibrating air molecules hit the membrane and make it move in a vibratory fashion, the latter will transfer the movement on the coil. The coil will move towards the magnet, and magnetic flux or magnetic lines will move inside the coil. As a result, electricity will be induced on the coil.
This is described in this link which includes a schematic representation of a dynamic microphone