What Is Compression in Audio? Understanding the Two Types

The word compression is often used in audio production, but it can mean different things depending on the context. Generally, compression refers to reducing something — either the dynamic range of an audio signal or the file size of an audio recording. While both processes are essential in modern audio workflows, they serve very different purposes.

Let’s explore the two main types of audio compression:

1. Dynamic Range Compression

– audio level compression, in which the dynamic range, the difference between loud and quiet, of an audio waveform is reduced

2. Digital Audio Compression

– Audio compression (data), a type of lossy or lossless compression in which the amount of data in a recorded waveform is reduced to differing extents for transmission respectively with or without some loss of quality

1. Dynamic Range Compression

Dynamic range refers to the difference between the quietest and loudest parts of an audio signal. For example, in a vocal recording, a singer might whisper one line and belt out the next. This can make the performance expressive — but also inconsistent or difficult to mix.

Dynamic range compression is a tool used to control those volume variations. It works by automatically reducing the volume of the loudest parts and, optionally, boosting the quieter parts. This results in a more balanced, even sound.

Key Features:

• Applied during recording, mixing, or mastering.
• Makes quiet sounds more audible and loud sounds less overwhelming.
• Helps instruments or voices “sit better” in a mix.
• Can add punch or presence when used creatively.

Common Uses:

Vocals, drums, bass, podcasts, and any content where consistency is important.

Different compression ratios for a signal level above the threshold (source Wikipedia)

2. Digital Audio Compression

Digital audio compression refers to reducing the size of audio files for storage or transmission. This is especially important when streaming music, sharing audio online, or storing large amounts of audio data.

There are two main types:

• Lossy compression (e.g., MP3, AAC): Reduces file size by permanently removing audio data that is less noticeable to the human ear. Some quality is lost.
• Lossless compression (e.g., FLAC, ALAC): Reduces file size without removing any audio data. The original sound can be perfectly restored.

Lossy audio compression is used in a wide range of applications. In addition to standalone audio-only applications of file playback in MP3 players or computers, digitally compressed audio streams are used in most video DVDs, digital television, streaming media on the Internet, satellite and cable radio, and increasingly in terrestrial radio broadcasts. Lossy compression typically achieves far greater compression than lossless compression, by discarding less-critical data based on psychoacoustic optimizations

Key Features:

• Applied during file encoding or export.
• Has nothing to do with how the audio is mixed or performed.
• Essential for streaming, archiving, and portable devices.

Common Uses:

Music streaming, podcast distribution, online video platforms, file sharing.

Summary Table

In Summary

Although both are called “compression,” these two processes do very different jobs:

• Dynamic range compression changes how the audio sounds.
• Digital audio compression changes how the audio is stored.

Understanding the difference is essential for audio engineers, musicians, and content creators. Each type solves a unique problem, and both are crucial to producing, sharing, and enjoying audio in the modern world.