CD with holes of increasing size
CD with holes of increasing size
CD with holes of increasing size

 

Code Number: 3E80.10

Demo Title: Digital Reproduction CD with Holes

Condition: Good

Principle: Digital coding and interleaving.

Area of Study: Oscillations & Acoustics

Equipment: 

CD with holes of increasing size, CD player and audio system.

Procedure:

Holes of increasing size have been drilled into this CD.  They are: # 80 (.25mm), # 75 (.45mm), # 60 (.9mm), # 50 (1.65mm), #31 ( 2.9mm).  Play the CD and you will see that the data on the CD is coded so as to override localized damage to the disc, correcting for "burst errors".  On this disc you will start to hear skipping on the third track somewhere between 2:45 and 4:00 minutes depending on the quality of the CD player.  This is approximately where the largest hole is drilled.

References:

  • Matthew Vick, "Digitizing Sound: How Can Sound Waves be Turned into Ones and Zeroes?", TPT, Vol. 48, # 7, p. 468.
  • H4 - 67, University of Maryland, Lecture Demonstration Site.