Thanks to our ears we can hear sounds produced by various devices such as horns, bells, bass drums, speakers, etc. Speakers today are in various electronic devices, being widely used to increase car sounds, as shown in the figure above.
We can simplify the definition of loudspeakers as components that transform electrical signals from an electric current into pressure oscillations in the air, in the form of a sound wave. If we look closely at a speaker, we can see that its basic components are a permanent magnet, attached to the speaker’s frame, and a moving coil, which is attached to the paper cone.
When we apply a variable electric current to the coil, it is repelled or attracted by the magnetic field of the permanent magnet. In this way, the coil-cone assembly is moved back and forth, pushing the air around it, creating a wave of compression and rarefaction in the air, that is, a sound wave.
For example, by applying an oscillating current of 440 Hz to the coil, the speaker cone will move back and forth at the same frequency, producing a sound wave of 440 Hz.
