How Does a Speaker Make Sound With Electric Energy?

A loudspeaker contains a metal coil, known as an electromagnet, that creates a magnetic field when an electrical current passes through it. It is the action of the electromagnet that is responsible for converting electrical energy into audible sound.

Electromagnetism

• Reversing the direction in which electrical current flows through the electromagnet reverses the poles of the magnet. This means that, depending on the direction of the current, the electromagnet is attracted to or repelled by a fixed, permanent magnet inside the speaker and vibrates back and forth.

Vibration

• The electromagnet is attached to a flexible cone, typically made of paper or plastic. The cone amplifies the vibrations of the electromagnet and creates waves in the surrounding air, which we hear as audible sound.

Frequency & Amplitude

• The frequency of the vibrations determines the frequency, or pitch, of the sound reproduced by the speaker. The amplitude, or strength, of the vibrations determines the volume of the sound.