# compact disc audio

> kind of optical disc

**Wikidata**: [Q107196246](https://www.wikidata.org/wiki/Q107196246)  
**Source**: https://4ort.xyz/entity/compact-disc-audio

## Summary
Compact disc audio (CD-Audio) is a type of optical disc designed to store high-quality digital audio. It was the dominant format for commercial music distribution from the mid-1980s through the early 2000s. CDs use laser technology to read binary-encoded audio data stored in pits and lands on a reflective surface.

## Key Facts
- **Classification**: Subclass of optical disc.
- **Primary Use**: Storage and playback of high-fidelity digital audio.
- **Data Encoding**: Uses pits and lands on a reflective layer to encode binary data.
- **Physical Format**: Flat, circular disc typically 120 mm in diameter.
- **Standard**: Defined by the Red Book standard developed by Sony and Philips.
- **Launch Year**: Commercially introduced in October 1982.
- **Capacity**: Holds up to 74 minutes (later extended to 80 minutes) of stereo audio.
- **Creators**: Jointly developed by Sony and Philips in the late 1970s.

## FAQs
### Q: What is a compact disc audio used for?
A: Compact disc audio is used for storing and playing back high-quality digital stereo audio. It became the primary medium for distributing recorded music from the 1980s onward.

### Q: How does a CD store audio?
A: A CD stores audio as a series of microscopic pits and lands arranged in a spiral track. A laser reads these variations to reconstruct the digital audio signal.

### Q: Who invented the compact disc?
A: The compact disc was co-developed by Sony and Philips during the late 1970s, with the first commercial release occurring in 1982.

## Why It Matters
The introduction of compact disc audio revolutionized the music industry by replacing analog formats like vinyl records and cassette tapes with a durable, high-fidelity digital alternative. Its error-correction capabilities and resistance to wear made it ideal for both consumers and broadcasters. As the first widely adopted digital audio format, it laid the groundwork for later developments such as DVD-Audio, SACD, and digital file-based media. The CD also played a key role in the rise of personal computing and portable audio devices, influencing how people consume and manage their music libraries.

## Notable For
- First commercially successful digital audio format.
- Superior sound quality compared to analog predecessors like cassettes and vinyl.
- Physical durability and longevity under normal conditions.
- Global adoption due to standardized specifications (Red Book).
- Enabled innovations in portable audio players and computer-based music storage.

## Body
### Technical Overview
Compact disc audio is based on digital encoding of sound using Pulse Code Modulation (PCM). Audio is sampled at 44.1 kHz with 16-bit resolution per sample, following the Red Book standard established by Sony and Philips.

### Physical Characteristics
- **Diameter**: 120 mm (standard size), though smaller 80 mm variants exist.
- **Thickness**: Approximately 1.2 mm.
- **Layers**: Polycarbonate substrate, reflective aluminum layer, protective lacquer coating.
- **Data Track**: Spiral path of pits and lands beginning near the center and extending outward.

### Development and Launch
- **Development Start**: Late 1970s collaboration between Sony and Philips.
- **First Release**: October 1982 in Japan; Europe and North America followed shortly after.
- **Initial Adoption**: Slow uptake initially but gained momentum throughout the 1980s.

### Specifications
- **Storage Capacity**: Up to 74 minutes of audio (extended to 80 minutes in some cases).
- **Channels**: Two-channel stereo by default; supports subcode data for track information.
- **Playback Speed**: Constant linear velocity (CLV) of approximately 1.2–1.4 m/s.

### Legacy and Impact
Despite declining sales since the 2000s due to digital downloads and streaming services, CDs remain relevant in niche markets and among audiophiles. They continue to serve as reference masters in professional audio production and are still used in automotive and legacy systems worldwide.

## References

1. [Source](http://www.tesauromuseus.com.br/detalhe-tesauro-ordem-alfabetica/disco%20compacto%20de%20audio)