Birthday of the Compact Disc

02
March 2020

Philips, Sony and Polygram produced the first compact discs. At the time, it was a true sensation. The CD had a 12cm diameter. Beethoven’s 9th Symphony was used as a demonstration recording, which lasted for 74 minutes. The then most popular version of the symphony had been recorded by laser and was read by a laser player. Gradually, optical discs started to carry other information beyond audio recordings. CD-ROMs, followed by CD-Rs and CD-RWs, could contain any digital information. CD-Rs allowed only one recording while CD-RWs allowed more than one recording with a possibility of deleting and rerecording information. The recorded data on the CD takes the form of a continuous spiral starting from the inside and moving outward. This spiral or track consists of a series of indentations called pits, separated by sections called lands. A tiny laser beam moving along the track reflects light back to a photo sensor. The sensor sees more light when it is on a land than when it is on a pit, and these variations in light intensity are converted into electrical signals that represent the music originally recorded. Algorithms of compressing information helped to considerably reduce the size of audio files without causing any problems for the human ear. МР3 became the most popular recording format. In the 21st century, flash technology made the Audio CD almost extinct just as the latter had previously made obsolete the vinyl records and the audio cassette.

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