Audio Recording, Compact Disk

The compact disk (CD) brought digital recording and playback technology within the reach of the average household. It offered a quality of sound reproduction good enough to satisfy the audiophile, unprecedented recording length within a compact format, and a system that did not damage sound quality with use.

These qualities made it far superior to the micro-grooved vinyl disk for the reproduction of sound, and it rendered this long- lived technology obsolete within a decade of its introduction. The technology employed in this product has been applied to a variety of uses, from data storage and retrieval systems to an integrated audio and video (play only) disk for the home user.

Methods of saving and reproducing data have been a major area of research for engineers and scientists from the nineteenth century onwards. Many of the technologies developed have found applications in home audio—from Edison’s revolving wax cylinders in the 1880s to magnetic recording tape in the 1940s. At every step, the accuracy of reproduction, the range of sound frequencies captured, and the durability of the recording medium have been progressively improved to reach its zenith with the compact disk.

In the 1960s and 1970s technologies from several different areas of this research were combined into a system of digital encoding and retrieval using optical readers to retrieve the data and computer sampling to turn analog sound into digital code. Much of the research was aimed at video recording, but it was soon applied to audio.

Many scientists and business executives involved in this corporate research were audiophiles who wanted a superior method of saving and reproducing sound. The revolving vinyl disk and the system of stamping copies of master recordings provided important paradigms in the research effort. The compact disk was first introduced as a commercial product in 1982 by Sony Corporation of Japan and Philips electronics of the Netherlands.

The research that led to the CD was carried out in the U.S., Japan and Europe. James T. Russell, a physicist at the Battelle Institute, invented a system of using light to read binary code in the 1960s. By 1970 he had a digital-to- optical recording system using tiny bits of light and dark—each about 1 micron in diameter— embedded on a photosensitive platter.

A laser read the tiny patterns, and a computer converted the binary code into an electrical signal that could be converted into audio or video streams. I.S. Reed and G. Solomon published a multiple error correction code in 1960 that would be employed in the encoding of data on CDs to detect and correct errors.

In Japan the NHK Technical Research Institute exhibited a pulse code modulation (PCM) digital audio recorder in 1967 that sampled sound and saved the binary data to videotape. Two years later Sony introduced a PCM recorder, and in 1978 it offered a digital audio processor and editor, the PCM-1600, to record companies and radio stations, which used them to make master recordings.

Credit for the idea of the compact disk is usually given to Klaas Compaan, a physicist working for the Philips Company. In 1969 he realized that an RCA system of stamping copies of holograms could be used to reproduce disks holding video images. With his colleague Piet Kramer he devised a glass disk on which they recorded video signals, along with a track of dimples to record the analog sound signal, that were read with a laser beam. They then moved to recording a digital code on the disk and used a digital-to-analog converter to reproduce sound from the encoded binary stream.

In the 1970s Philips, Sony, and several other companies introduced digital systems to save video and audio. In 1978 35 manufacturers of digital recorders met in Tokyo. Philips took the lead in establishing standards for the format of the audio system: the diameter of the disk was finally set at 120 millimeters; the sampling rate was to be 44.1 kHz; and a 16-bit standard was adopted for the encoding of the audio signal. This enabled 74 minutes of sound to be recorded on the disk. Manufacturers agreed to run the data track from the inside to the outside of the disk and use a polycarbonate material (developed by Polygram, a subsidiary of Philips) for the disk substrate.

Philips and Sony collaborated in the development of prototypes, and in 1980 they proposed a set of standards whose worldwide adoption was an important factor in the success of the compact disk. In 1983 CDs were first introduced in the U.S., and 800,000 disks were sold; in 1986 53,000,000 were sold. By 1990 an estimated 1 billion CDs were sold globally. Within a few years after the introduction of the compact disk player, smaller units were available as car stereos and personal audio systems.

Several other products were quickly developed from the technologies used in compact disks. Compact video disks ranging from 120-300 mm in diameter were introduced in the 1980s. CD- ROM (Read Only Memory) units were developed as high-capacity data storage systems for computers. In the 1990s CD-I (Interactive) technology was introduced to merge interactive combinations of sound, pictures, computer texts, and graphics in one format. A combined audio and video 120 mm disk system (Digital Versatile Disk) was launched in 1996, which went on to successfully challenge the VHS video tape cassette recorder.

The compact disk quickly proved to be far superior to its vinyl distant cousin. Not only did it sound better and hold much more music, it was also free of the scratches and background noise that had become an accepted part of sound recording and reproduction. Yet it failed to dislodge the compact magnetic tape cassette from its preeminent position in home audio because it was a play-only format.

The union of Sony and Philips was broken in 1981 and the two companies went their separate ways to develop compact disk technology and devise a suitable recorder. Several different systems were introduced in the 1990s ranging from Sony’s Mini Disk recorder to the recordable CD-R used in home computers. The popularity of downloading MP3 files from the Internet and burning the sound onto recordable CD-Rs has made this format the most likely successor to the cassette tape.