How is electricity transformed into sound?

1. Sound is energy.

2. Energy can be converted from one form to another.

Picture a microphone. A simple device that has a permanent magnet, a coil of copper wire, and a thin diaphragm.

The copper wire is coiled around a thin cylinder of paper so that it encircles the magnet without touching it.

That coil is attached to the diaphragm and positioned over the magnet.

When sound hits the thin diaphragm, the diaphragm vibrates moving the the copper coil back and forth over the magnet. This action creates electrical impulses in the coil. This is energy conversion.

To see this in action, take a speaker apart. A microphone and a speaker work on the same principals only in reverse.

If you connect a volt meter to the leads on a speaker and move the cone, you'll see the meter register small amounts of electricity.