What Is Lossless Audio? How Music File Formats Work

Lossless audio can refer to both uncompressed audio file formats and lossless compressed audio file formats. Music streaming services use both lossless compressed files and lossy compressed files. Understand what each of these music formats means, learn how to tell them apart, and find out which one makes the most sense for your use.

What are audio file formats?

An audio file format is a type of file used to store digital audio data on a storage medium such as a microSD card, an HDD, an SSD, or a CD (Compact Disc).

These storage media are used together with a device responsible for playback (execution) of audio files, such as a computer, a smartphone, a Digital Audio Player (DAP), or a CD player (Compact Disc player, popularly known as a “Discman”).

What types of audio file formats are there?

There are many types of audio file formats, but we can divide them into three main categories:

• Uncompressed audio files
• Lossless compressed audio files
• Lossy compressed audio files

What are uncompressed audio files?

Uncompressed audio files are the result of encapsulating raw PCM (Pulse-Code Modulation) data with metadata [1]. PCM is a method used to digitally represent analog audio signals.

The main uncompressed music formats for local playback are:

• AIFF
• WAV

[1] Metadata is information about a song, such as title, artist, album, year, track number, and musical genre.

What are compressed audio files?

Compressed audio files use different audio codecs [2] to reduce file size. A codec implements an algorithm to compress and decompress the digital audio signal. The goal of compression is to represent the audio signal using as few bits (digital data) as possible while trying to maintain sound quality.

[2] Audio codecs are hardware components (electronic circuits) or software (programs) designed to encode (compress) and decode (decompress) a stream of bits (digital data), also known as bitrate.

What are lossless compressed audio files?

Lossless compressed audio files are between 50% and 60% the size of uncompressed audio files (WAV and AIFF). They do not suffer from information loss related to the sounds in a piece of music thanks to a technique called silence compression.

The main lossless compressed music formats for local playback are:

• ALAC
• FLAC

Uncompressed files vs. lossless compressed files: What’s the difference?

Uncompressed audio files treat moments of silence and moments of sound in a recording using the same number of bits. As a result, a song that contains periods of silence and sound will have the same file size as a track in which every second is filled with sound.

When using lossless compressed audio files, the codec’s algorithms apply silence compression, a technique used to reduce the bitrate (data flow) and the file size of the music. In this way, the sound data of the track is preserved while the space occupied by the file is reduced.

What are lossy compressed audio files?

Lossy compressed audio files remove part of the data related to the sounds in the music, resulting in an even smaller bitrate and file size compared to lossless compressed files.

The algorithms used in lossy codecs are based on psychoacoustics, which deals with the limitations of the human auditory system in perceiving certain sounds. Thus, the goal of this compression process is to remove only sounds that are less audible or harder to perceive.

Examples of sounds that are harder to hear include:

• Certain frequency ranges in the upper treble region (12 kHz to 20 kHz or higher)
• Sub-bass frequencies below 50 Hz
• Sounds that occur simultaneously with louder sounds

There are two categories of lossy compressed audio file formats:

• Formats designed for local audio playback, typically used with wired headphones or speakers
• Formats developed for wireless Bluetooth transmission, intended for Bluetooth headphones or speakers

The main lossy music formats for local playback are:

• AAC
• MP3
• MQA
• Ogg Vorbis
• Opus

For lossy formats used in Bluetooth transmission, the most popular ones are:

• AAC
• aptX
• aptX Adaptive
• aptX HD
• LDAC
• SBC

Is there a perceptible difference in audio quality between lossy and lossless files?

In practice, it is difficult to perceive differences in sound quality between lossless and lossy compressed audio files. Lossless audio files are useful for music production (recording, mixing, and mastering) or for archiving purposes (preservation of historical material for documentation).

However, note that although the differences between lossless and lossy formats are small, you may perceive differences in sound quality between music streaming services. This is due to the existence of different versions of the same album, each with a different mastering.

If you want to check a specific work (album), simply visit the Dynamic Range DB website using the provided link and use the search bar located at the top right of the page. There, you can check the Dynamic Range (DR) [3] of each album.

[3] Dynamic Range (DR) is the difference between the loudest and quietest sounds in a piece of music. The smaller the DR, the harder it becomes to hear certain sounds or nuances, because in this case all instruments and voices are at very high volume levels, causing masking of musical details.