If you were to look closely at the surface of a CD under a microscope, you would see a spiral track with bumps of uniform height in polycarbonate plastic with a shiny aluminum backing. The bumps are extremely small: about 0.5µm wide, a minimum of 0.83µm long and 0.125µm high. (A human hair is about 1µm wide.)

When the CD is placed in a CD player, the CD is spun at 200 to 500 rotations per minute while light from a laser scans over the CD. Depending on whether the light hits the top of a bump or not, the light is reflected differently. This reflection information is translated into bits of high and low electrical signals.

But how do these bits of high and low electrical signals turn into the music from your speaker? The electronics in your CD player then read a collection of bits to make up a byte of information. Each byte (which can have one of 65,536 values) accurately represents the original acoustic signal or music with high fidelity so that it sounds virtually perfect to the human ear.