1. How is sound captured for a CD
Every second 44,100 samples are taken.
Each sample is converted into a 16-bit number. (16 bits allows for 65,500 numbers)
These numbers are stamped into the metallic layer of a CD

2. CD Rom- Digital data storage
Data is represented as edges between pits and bumps
Track is a outward moving spiral

3. CD Bumps are the digital data - approx. 640 MBytes
Data Track is typically 3 ½ miles long.
Human Hair width is about 100 um (microns)

4. Reading the bumps with a laser and optical sensor

5. Click for animation
Pit Edges cause some light to reflect off of the bump and some to reflect off of the pit. These two reflected beams are “out of step”. They interfere with each other causing the total reflected light to be dimmed.

6. The tracking drive keeps the laser under the track that is being read.
The disk motor spins between rpm as the laser moves outward with the track.
Animation at:

7. How data is arranged on CDs
Data is interleaved so scratches on the CD won’t be a complete loss of data
Data is read one revolution at a time, and software orders the interleaved data in the correct sequence.
Extra data is present for error-checking
Meta-Data is present to identify songs