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Alessandro Fois

Pianist, Composer, Arranger, Sound Engineer, Writer, Blogger

Alessandro Fois is a musician, composer, pianist, arranger and sound engineer. Since 2018, he has also been a writer, blogger and webmaster. He currently resides in Ivrea (Turin) where, in addition to the above activities, he manages Lycnos, studio for audio, video and web services, and the recording studio Glamour Recording Studio.

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Mastering Guide for Streaming Platforms: Normalisation, LUFS and Loudness

With the 84% of digital music consumed via streaming in 2023, it has never been more important to understand how to optimise mastering for platforms such as Spotify, Apple Music and many others. This step-by-step guide will walk you through understanding and applying essential concepts such as loudness, LUFS and normalisation to ensure your music resonates at its best wherever it is heard.

What is Loudness and Why is it Important in Mastering

Definition of Loudness

Loudness represents the perception of the volume of a sound, but it is not an absolute concept. It depends on:

• The sound pressure (SPL) in the environment.
• Audio characteristics, such as frequency distribution.
• The individual sensitivity of the listener.

To measure loudness objectively in the digital domain, instruments such as the loudness meterswhich adopt universal standards to quantify their perception.

LUFS: The Loudness Measurement Standard

LUFS (Loudness Units Full Scale) is the globally recognised unit of measurement for perceived loudness. LUFS meters simulate human hearing through a process called K-weighting, which:

• Attenuates frequencies below 100 Hz.
• Amplify those above 2 kHz.

LUFS gauges offer five main metrics:

1. Momentary Loudness: It measures the RMS level over a 400 ms time window.
2. Short-Term Loudness: Similar to the previous one, but over a 3-second window.
3. Integrated Loudness: It calculates the weighted average of a song, excluding very low signals (-70 LUFS) and moments that are too quiet (-10 LU compared to the average).
4. Loudness Range (LRA): It assesses the dynamics of a song, from high levels (e.g. classical music, 20 dB) to extreme compression (e.g. metal, 3-4 dB); in modern pop, an average of around 5-8 dB can be considered optimal between the need for compression and respect for expressive dynamics.
5. True Peak: It measures the actual peaks of a digital signal, taking into account any distortions introduced by the digital-to-analogue conversion (DAC).

K-weighting: Filter introduced in the ITU-R standard BS.1770 (2006) by the International Telecommunication Union (ITU) to measure perceived loudness. It simulates human sensitivity by attenuating frequencies below 100 Hz and emphasising those above 2 kHz. Based on previous studies such as A-weighting, it improves the representation of loudness in professional contexts such as broadcasting and streaming. Developed in collaboration with international experts, including Eelco Grimm and Thomas Lund, it is designed to offer a more accurate and consistent measurement than listeners' actual perception.

Normalisation: What It Is and How It Affects Mastering

The Concept of Normalisation

Normalisation adjusts the loudness of a track to a predefined level to ensure a uniform listening experience. In streaming platforms, the reference is often the integrated loudness (LUFS), not maximum peaks. This ensures that volume variations between tracks are minimal, providing a pleasant and consistent listening experience.

The Objective of Standardisation

The aim is not to standardise the work of sound engineers, but to offer the end user a consistent experience. However, standardisation allows sound engineers creative freedom, since:

• More dynamic pieces (such as classical music, traditional jazz and more 'orthodox' world-music) can retain their naturalness.
• More compressed tracks (such as pop, dance, metal and others) can achieve higher loudness, being then adapted by the platform.

Mastering for Streaming Platforms

Should I burn at -14 LUFS?

Not necessarily. Although many platforms have a reference of -14 LUFS, it is not mandatory to follow it. Here are some considerations:

1. Artistic Intention: Sound quality and artistic coherence must be a priority.
2. Differences between Platforms: Apple Music uses -16 LUFS, Deezer -15, and Pandora is not based on LUFS.
3. Evolving Specifications: Reference levels may change over time.

The best approach is to create a master that expresses the full sonic potential of the track, without sacrificing dynamics or quality. However, it is good to specify that in 2024, the recording industry's trend is to master at between -9 and -7 LUFS.

This approach seems to exhume the nefarious practices implemented during the period of the Loudness Warpartially abandoned around 2005. In fact, elevated compression levels in mastering seem to have made a comeback in pop music since the 2000s in particular, but with better results than then, thanks to improved digital tools and more efficient step-by-step control techniques during the mastering process,

True Peak Management and Album Balancing

The True Peak represents the maximum level an audio signal can reach after conversion from digital to analogue. Strict control of this parameter is crucial to avoid clipping and distortion, especially with the spread of the lossless streamingwhich fully preserves the original signal.

Streaming Lossy

Lossy formats, such as MP3 and AAC, reduce file size by removing sound information, but compression can generate higher peaks to the levels visible in the original files. To prevent unwanted artefacts during playback, it is recommended to keep True Peak below -1 dBTPleaving a sufficient margin to compensate for any over-peaks introduced by the coding process.

Lossless streaming

In the case of lossless streaming, which uses codecs such as FLAC or ALAC to transmit audio without loss of quality, the signal retains full fidelity to the original source. However, stricter control of peak levels is necessary. The traditional limit of -0.3 dBTP, typical of CD mastering, may not be sufficient to guarantee flawless reproduction, especially on sensitive devices. It is therefore recommended to keep True Peak below -1 dBTP for greater security.

N.B.: In extreme cases, such as highly compressed audio or very low bitrates, a margin of -2 dBTP to avoid distortions.

Recommended Mastering Chain

To ensure control of True Peak and prevent problems in any context, we recommend:

1. A standard limiter set to -1 dBFS to manage general levels.
2. A True Peak limiter configured at -1 dBTP (or lower in more complex cases) to avoid clipping specifically.

Careful control of True Peak not only guarantees distortion-free audio, but also preserves sound quality, making it compatible with all playback platforms and devices, in both lossy and lossless formats.

Balancing Albums

For albums, platforms follow two approaches:

• Track Normalisation: Each track is individually normalised (Amazon, YouTube, Deezer).
• Album Normalization: The entire album is adapted to the level of the strongest or average song (Spotify, Apple Music).

This preserves the dynamic balance desired by the artist, but suggests to the mastering engineer to do a careful balancing check between the perceived volume ratios within the same album.

The choice between the two approaches is specified in the table below, in the column Mode.

Loudness Specifications for Major Platforms

Here is a table including loudness specifications and True Peak levels for the main streaming platforms, SoundCloud and the audio CD:

Notes:

• SoundCloud: Does not apply loudness normalisation and does not specify a reference level in LUFS. However, it is advisable to keep True Peak at -1 dBTP to avoid distortion during playback.
• Audio CD: There is no LUFS standard for audio CDs. Traditionally, the maximum allowed peak level is 0 dBFS. However, many professionals prefer to keep True Peak at -0.3 dBTP to prevent clipping during playback on different devices.

Final Guidelines for Optimal Mastering

1. Serve the Music: The loudness of the mastering must respect the artistic intention and not bend to rigid standards.
2. Manage Levels: For pop, an integrated level of around -12 LUFS, with peaks below -1 dBTP, works well on all platforms, but is less suitable for typical audio CD and SoundCloud habits; moreover, it is good to know that in pop and derivatives the trend of the year 2024 is a finalisation to -9/-7 LUFS. For high-dynamic genres such as classical music, it is often better to stay between -23 LUFS (maximally purist approach) and -14 LUFS (maximally progressive approach, but in that case it is better to have compression applied to the entire dynamic range of the track rather than using 'wild limiting' on the peaks.
3. Preserves Dynamics: Don't sacrifice dynamics to bring loudness closer to arbitrary reference levels, keep the LRA high enough for music.
4. Maintain maximum cleanliness of sound and dynamic coherence, and absolutely avoid all of the following:
   1. mechanical' distortion caused by the limiter's intervention rating: if you use zero time in attack, always use the maximum LookAhead value; if you use a slower attack to better preserve transients, you can decrease it to obtain more loudness
   2. the 'breathing' of the compressor (i.e. the sudden lowering of the volume after each peak, and then the subsequent more or less rapid but audible rise in volume
   3. where it is not possible to avoid the above, compress the entire dynamic range of the track before the limiter intervenes, using a very low ratio (maximum 2:1, but often much less is sufficient, which also allows you to use very fast attack and release values); in this way, the limiter intervention will be more moderate, preventing the above-mentioned problems
5. Perform detailed mastering editing: If a specific point in the song causes you dynamic problems that are difficult to resolve in the mastering phase, you could apply (using the automations) different volume, compression or limiting parameters only at those specific points (sometimes even a drastic intervention over a duration of a few milliseconds may be necessary, to extinguish the exuberance of an extreme peak of short duration, without significantly mortifying the impact of the transient; if the same problem occurs only on specific frequency bands, you could use (before limiting) a compression targeted only on the specific tonal band.

With these pointers, your mastering will be technically accurate and musically respectful, adapting to both current and future standards.

Tonal balance in mastering

See also this other blog article

Mastering Guide for Streaming Platforms: Balancing Equalisation and More

For more on Digital Audio Mastering

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