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An optical disc that is used specifically to store digital audio data is known as an audio compact disc. Also known as a CD, the main design has been available to the public since 1982 and remains one of the most prevalent forms of data storage well into the 21st century. Audio CDs are primarily used by the music industry to release albums and audio tracks and also for burning or copying discs in computers. The standard version is 4.7 inches (120 mm) and can hold 80 minutes of audio.
Both Philips and Sony began to design the audio compact disc in the late 1970s. The general idea was stimulated by the early quality of Laserdisc™ technology. Both companies had rival ideas and decided to unite to determine a standardization. By 1980, the technology was ready for consumer use and preparations were made for commercialization. Sony released the first compact disc player called the CDP-101 and the first CDs began to be pressed. Throughout the 1980s and early 1990s, much of the music industry's catalog was converted to audio compact disc.
The original concept of the compact disc was to replace the traditional vinyl record. However, the format revolutionized digital media in other ways that were not predicted. With the advent of burnable audio compact discs, people were able to make their own copies of albums. This had detrimental effects on the profits of the recording industry in general. In addition, further understanding of how the process worked sparked a growth in alternative mediums such as MP3. Essentially, the audio compact disc brought the concept of the “audio file” to the public.
The physical design of a compact disc is standardized by the early agreement between Sony and Philips. It is made of polycarbonate plastic that measures 0.05 inches (1.2 mm) thick and weighs 0.6 ounces (16 grams). A layer of dyed metal is placed on the surface. This part is the portion that holds the information. The tint of the reflectivity is what determines the data that is held on the CD. As a laser directs a beam onto the surface of the disc, a photodiode reads the reflection and sends a signal to an device which plays the audio.
One drawback of audio compact discs is the fragile nature in which they are designed. A variety of daily use and exposure to elements can do detrimental damage to the format. Scratching on either side of a compact disc can cause the information to be misread. This is known as skipping. A cheaper audio compact disc as well as those released during the 1980s often suffer from something known as “CD rot.” This is the degradation of the reflective surface over time from repeated exposure to the laser.
People have actually been making illegal copies of albums for years. When cassettes were standard, people used to copy those on dual-deck tape recorders or record directly from albums. So, there was nothing new in that regard as far as piracy goes -- the media used was just different.
What was revolutionary was that people figured out how to take those huge audio files from CDs, compress them into MP3s and make them available on the Internet. When broadband Internet connections became the norm, stealing a whole album that had been converted into small MP3 files became very easy and fast.
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