Microphones are transducers that convert one form of energy into another. Microphones convert sound energy into electrical energy and speakers convert electrical energy into sound energy. Before we get into how they work, let us understand some basic properties of sound waves.
Sound waves are longitudinal in nature composed of ‘compressions’ and ‘rarefactions’. These are nothing but a variation in pressure. Area of increased pressure is called compression and area of decreased pressure is called rarefaction. Sound needs a medium to travel and it travels as waves of air pressure fluctuations. We hear different pitches depending on the frequency and amplitude of sound waves.
There are around ten types of microphones. Though the energy conversion takes place in different methods, the basic feature present in them is the diaphragm. It vibrates when it detects sound waves. The diaphragm is attached to a coil. Because of the vibrations, the coil moves backward and forward around a magnet. Thus current is generated.
Some microphones also have built-in amplifiers to boost the signal as the electric current produced by the microphones is very small. The speakers at the other end are also transducers that convert the electrical signals back to sound waves.