Audio files are delivered to Spotify from distributors all over the world and are often mixed/mastered at different volume levels. We want to ensure the best listening experience for users, so we apply Loudness Normalization to create a balance.
It also levels the playing field between soft and loud masters. Louder tracks have often been cited as sounding better to listeners, so Loudness Normalization removes any unfair advantage.
Note: The web player and Spotify apps integrated into third-party devices (such as speakers and TVs) don’t currently use Loudness Normalization.
How does Spotify adjust loudness?
When we receive your audio file, we transcode it to delivery formats Ogg/Vorbis and AAC. At the same time, we calculate the loudness level and store that information as metadata in the transcoded formats of your track.
Playback levels are not adjusted when transcoding tracks. Tracks are delivered to the app with their original volume levels, and positive/negative gain compensation is only applied to a track while it’s playing. This gives users the option to adjust the Loudness Normalization if they want to.
- Negative gain is applied to louder masters so the loudness level is at ca - 14 dB LUFS. This process only decreases the volume in comparison to the master; no additional distortion occurs.
- Positive gain is applied to softer masters so that the loudness level is at ca - 14 dB LUFS. A limiter is also applied, set to engage at -1 dB (sample values), with a 5 ms attack time and a 100 ms decay time. This will prevent any distortion or clipping from soft but dynamic tracks.
The gain is constant throughout the whole track, and calculated to match our desired output loudness level.
