Moving coil Microphone & Loud Speaker

Moving coil Microphone
Microphone is an instrument which can convert sound signals to electrical signals continuously. Today different types of microphones are in use. They work under different theories. Here we are going to study about moving coil microphone.
Voice coil is an important part of moving coil microphone and it is a coil of very thin insulated wire. The voice coil is designed such that it can vibrate freely in between the poles of a magnet. This coil is connected to a diaphragm.
Let’s see how the microphone converts sound signals into electrical signals.
The diaphragm vibrates when sound signals incident on it and voice coil also vibrates in accordance with the diaphram. These vibrations cut the flux lines and thus electrical signals are induced in the voice coil. These signals are strengthened by using an amplifier and send to a loud speaker.

Moving coil Loud Speaker
The structure of moving coil loud speaker is same as that of the microphone. The important part of a loud speaker is permanent magnet, voice coil and a diaphragm.
The voice coil is placed between the opposite poles of the permanent magnet. A paper cone or a diaphragm is attached to this coil. The electrical signal corresponding to the variations of sound from the microphone is amplified by an amplifier and is fed to the voice coil. The voice coil placed in the magnetic field vibrates in accordance with the intensities of the electrical signals. These vibrations induce vibrations on the paper cone attached to the coil causing vibrations to the air around it. As a result original sound is reproduced more loudly.

It is only after the discovery of electromagnetic induction, that the large scale production of electricity became possible.