Video: Loudspeaker (How it works?)

Sound is a mechanical wave – also called an acoustic wave. To produce sound, it is necessary to set molecules of air in motion.

This animation represents a loudspeaker. It is an electromagnetic  transducer that transforms an electrical signal into a mechanical signal.

(…)

It is made up of:

• a  flexible membrane in direct contact with the medium of propagation (…)
• a  conducting wire coil (…)
• a permanent magnet that encircles the coil (…)
• a rigid container that holds everything together 

(…)

Note, because it is important, that the flexible membrane is connected to the electrical coil, which is able to move freely along the length of its axis.

The principle behind the functioning of this device rests on magnetic forces, to  which the coil  is subjected when a current is flowing through it.

(…)

Let’s look now at the physical chain of events:

The coil vibrates at the rhythm of the electrical signal, carrying the flexible membrane along with it.

The membrane transmits the mechanical vibration to the molecules of air around it and the wave is propagated, successively, to nearby neighbors, like a wave in water, at a speed that is approximately 1000 km per hour.