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Story of CDs

A standard CD will have a diameter of just 12 cm and about 80 minutes audio data can be saved on it. Smaller CDs are also manufactured for storing single songs (called CD singles). They are 8 cm in diameter and can save 24 minutes of audio data.
The key research and improvement work was done by Phillips and Sony. One of the first CDs came in market way back in the year 1982 and till date, remains one of the most common means of audio recordings.

In 1979, Phillips and Sony started off a joint working group in order to model a successful digital audio disc. After a year`s work and lot of experiments and planning, the compact disc was invented. No sole person can be said to have invented it, a large group collectively invented the compact disc.
In August, 1982, the earliest CD for commercial purposes was manufactured in a Phillips factory in Germany. The first music title that was released on a CD was `The Visitors (1981) by ABBA`. Soon after, in October of the same year, the CD players from Sony also reached the markets. The incident is often called as `the Big Bang` in the area of digital audio.

The new concept was an immediate success in the market. Customers were enthusiastic about the superiority of the audio on the CDs. The price of CD players sank really fast, as a outcome of which, the popularity amplified even more.

A Compact Disc is a 1.2 mm thick polycarbonate plastic disc weighing around 16 grams. To make the plane reflective, a very thin layer of aluminum is applied on one side of the disc. A film of lacquer is also applied to act as a protecting shield. The label is printed on the other side using normal printing process like offset or screen printing. The data is saved on a CD in shape of an array of tiny grooves called pits that are encoded in a spiral track. A pit is just 500 nm wide and 100 nm deep and the length varies from 850 to 3500 nm.

The CDs are much more long-lasting than the preceding formats of audio storage. However, they can be spoiled a little from the environment factors and daily usage. The data is a lot nearer to the label side, so more damage occurs if scratches are made of the label. The logical format to store audio data on a CD is a 2-channel 16-bit PCM encoded data at a sampling rate frequency of 44.1 KHz. The sampling rate was chosen directly as a result of the sampling rate theorem of double frequency needed in recordings. With some more calculations, the exact sampling rate of 44.1 KHz was decided.

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