Using software called Dynameter , this collection of audiophiles took measurements of popular playlists like the Global Top 50 and albums of genres ranging from soul to metal, and discovered that the Spotify catalog had become quieter.

At the end of May, Spotify made a change to its music files that went unnoticed by almost all of the service's listeners. What was apparent, however, to sound engineers and studio wizards was that the volume had been reduced on every Spotify-hosted track.

What sound engineers have come to realize is that Spotify has reduced the LUFS index of everything on its platform from -11 LUFS to -14 LUFS, a number in line with that of competing musical platforms like YouTube (- 13 LUFS), Tidal (-14 LUFS), and Apple Music (-16 LUFS). In practice, the volume for human ears will be more controlled, and you may not even notice the change.

Unlike RMS, another measure used to determine the average volume of audiovisual productions, LUFS ignores low frequencies, instead focusing on average and high measures above 2 kHz—the most sensitive region for our ears. A scream, for example, carries more volume sensation than a double bass might, although RMS indicates higher numbers for the instrument (and basses weigh heavily with the old measure). This is because the human voice is in the middle region.

It was only in 2011 that the European Broadcasting Union, one of the main broadcasting organizations in the world, established a measurement unit of loudness with the EBU-R128 standard , called LUFS (acronym for Loudness Units relative to Full Scale). It is, in fact, a smarter unit of measure than decibels for understanding human perception of volume.

We consider "loudness" to describe the human perception of a rich sound. When you listen to something, therefore, what really counts is the perception of that sound, not the values that are registered on a decibel meter.

We reached out to Spotify for comment about the LUFS reduction: "Spotify is always testing new features to benefit its users. Recent changes in the playback experience are part of the aspects we are evaluating."

So why is this important?

A better sound

Initially, the approval of the EBU-R128 standard was not aimed at streaming platforms and the music world. The intention was to normalize the sound patterns of televised content. You know how some commercials are way louder than others? Or the difference in the volume between a TV program and an ad? The goal of the EBU-R128 standard was to streamline those differences and standardize the volume of TV channels.

One of the main techniques for boosting the volume perception of a song is through compression. It can be performed with specific hardware or programs during the mastering process. As the name implies, the technique compresses the sound wave. This places a ceiling on the waves' peaks while promoting the gain in the lower parts. Imagine taking an electrocardiogram and tightening those gauges so that the higher and lower parts are more level.

"While trying to boost the sound, they ended up sacrificing its quality."

"If you compress an orchestra, and the violinist is playing a smooth violin by himself, you're going to hear it loudly," explains Pedro Luce, a Brazilian music producer. "When the rest of the musicians come in with their instruments, you'll hear everything with the same intensity." The compression intensifies the calmest, emptiest moments of the song.