Speaker is a device which converts electrical signal into sound waves. By
its property, sound is made when an object makes the particles around it
vibrate. These vibrations travel through the air, and reach our ears. Our brain
interprets this motion as sound. The amplitude of the waves corresponds to the volume level we hear and the frequency decides the nature of sound.
These vibrations are set up by the speakers using a set of magnets. One them
is a permanent magnet and the other is an electromagnet. To make these
vibrations, speakers have a set of magnets. One of them is called the permanent
magnet. The permanent magnet is fixed and the electromagnet is a coil of metal wire like copper or aluminum, fixed to the diaphragm. When an electric current is sent through the electromagnet, it is either attracted to or repelled away from the permanent magnet. The polarity of the coil can be reversed depending on the current. This back and forth movement causes the diaphragm or cone to vibrate, because it is connected to the magnetic coil. This is the sound that we hear.