1. Speakers Microphones

2. What is sound? A vibration
A microphone is a transducer, something that converts on type of energy (sound) to another (electrical)
All microphones have diaphragm. A piece that vibrates when you speak into it.

3. Carbon microphones
A carbon microphone is a circuit with a power supply and a pile of carbon that will be squished together by the vibrating diaphragm.
This carbon acts as a resistor to the current.
This changes the current.

4. Dynamic microphones
In this type of microphone, the diaphragm moves a magnet through a coil of wire, making an electric current like a generator

5. Condenser microphone
This type of microphone uses a capacitor behind the diaphragm.
An external power source creates a current and the capacitor affects the current.

6. The current
Since the resistor is vibrating the current changes with the frequency of your voice, or whatever sound is present.
That current is now a representation of the sound, or an audio signal.
A current can travel across a wire (old phone lines)
It can also be sent by electromagnetic wave (radio, cell phones)

7. Electromagnetic wave (EM wave or radiation)
Electromagnetic waves need no medium to travel through.

8. Electromagnetic waves
Electromagnetic waves can hit an antenna causing the current to reform
If they are sent a long distance a disc that acts like a convex mirror can force a large number of rays into a smaller point

9. Converting the current back into sound
A speaker converts the current created by a microphone back into sound.
The current runs through a coil of wire.
This creates an electromagnet.
The coil is in front of a permanent magnet.
That makes the speaker VIBRATE because of the magnetic force.
The speaker is placed in a diaphragm that acts as a sounding board.