Developments in loudness normalization are coming thick and fast, these days – and TIDAL just raised the bar.
Quality has always been one of the major selling-points of TIDAL’s streaming service – it’s one of the few places that lossless streaming is available, still. And that means they’ve been wanting to enable normalization by default in their players for some time. So that we won’t be blasted by sudden changes in level, which is a major source of user complaints.
But there’s a problem…
…and it also relates to quality.
Most normalization right now is done on a track-by-track basis, meaning all songs are played back with similar loudness. This seems to make sense for shuffle or playlist listening, but it doesn’t work for albums, where it changes the artistic intent.
You spend days, weeks, months crafting the perfect balance for your music, including from song to song – why would you want a computer changing that ? Research shows that only 2% of albums in TIDAL’s catalogue have songs that are all the same loudness, even in the current ‘loudness war’ era. So messing with that balance is something TIDAL really want to avoid.
The solution to this challenge seems straightforward, and it’s called Album Normalization. Instead of making all songs play with the same loudness, you measure the overall loudness of a whole album, and adjust all the songs by the same amount. The overall level is managed, to prevent “blasting” and improve the user experience, but the artistic intent is preserved.
Simple, right ?
Well… not necessarily. As usual, the devil is in the details. How does the playback software detect the difference between Album or Shuffle mode ? What should happen in Playlist mode ? And what happens when you switch between them ? If the user starts listening to a song in Shuffle mode with “Track” loudness, but then chooses to listen to the rest of the album, the next track would have to be played at “Album” loudness, which breaks the loudness sequence… Apple have had album-style normalization for some time, but it still has some rough edges and bugs, especially on mobile.
And even at a more basic level, users want things to be simple. The more options, the more potential for confusion. Spotify’s normalization has been in place for years, but many people still aren’t clear on exactly how it works.
TIDAL’s approach to this challenge was refreshingly simple – they asked an expert to research the best solution. That expert was Eelco Grimm, one of the original architects of the loudness unit measurement system, and a fellow member of the Music Loudness Alliance.
Eelco’s research was exhaustive and fascinating – you can hear all about it in my interview with him on the latest episode of The Mastering Show podcast in the player above, or read his findings in full on his website.
But here are the highlights:
Users prefer Album Normalization – EVEN in shuffle mode
This is the big one. Eelco analysed TIDAL’s database of over 4.2 million albums (!) and found examples with the biggest difference in loudness between the loudest and quietest songs. These are the albums whose dynamic structure will be changed most significantly by Track normalization, but would also presumably sound the most uneven when listened to in Shuffle mode.
Eelco built two random shuffled playlists, containing examples of these loud & soft songs, from 12 albums, with 7-10 dB of difference between the loud and soft examples. And he sent the playlists to 38 test subjects, who listened to them blind, and reported back on which ones they preferred.
I was one of those test subjects, and what I heard surprised me. The difference between the playlists was easy to hear. Album mode worked pretty well, but with Track Normalization, the songs didn’t sound equally loud ! Most would be OK, but then you’d suddenly have a song that is supposed to sound “loud” which felt too quiet, or a “quiet” song that sounded too loud. Album Normalization sounded better to me – more natural, more effective, more satisfying – even in shuffle mode.
And it wasn’t just me – 71% of the test subjects voted blind for Album Normalization, with a further 10% saying they would prefer this method by default. That’s over 80% of people preferring Album Normalization, all the time. Even when listening to Playlists, or with Shuffle enabled.
And with the benefit of hindsight, it’s not hard to see why. These albums were all mastered with care, meaning the relative levels of the songs worked on a musical and emotional level. If they worked in the context of the original album, why wouldn’t they work in shuffle as well, once all the albums were playing at a similar loudness ?
That leads us to another interesting finding, though.
Normalizing to the loudest song on an album sounds better than using the average loudness
Apple and Spotify both use the average loudness of each album for their Album Normalization, but Eelco recommended that TIDAL normalize to the loudest song of each album instead. Again, the reasoning behind this is straightforward.
Imagine an album with many soft songs and just one loud song, in comparison to one where all the songs are loud. If the overall loudness of these albums is matched, the loudest song on the album with “mostly quiet” songs will end up playing louder than the songs on the “all loud” album ! This doesn’t work artistically, and also opens the door for people to “game” the system and try to get some songs louder than most others. In contrast, matching the loudest songs on each album and scaling everything else by the same amount plugs this loophole, and keeps the listening experience consistent for the user.
(In fact, it’s exactly the strategy I use myself, when making loudness decisions in mastering, too.)
There were plenty of other interesting findings in Eelco’s research, too – we go into them in the podcast and I recommend you take a listen, even if you’re not that interested in normalization. But right now I want to move on to some…
It happens all the time: The Company has a problem. The Company commissions research. The research comes back, and tells The Company something unexpected, or unwelcome. The Company ignores the research.
But not TIDAL. Not only did they accept the findings of Eelco’s research in full, they paid attention and implemented his recommendations. And we learned yesterday that their new loudness normalisation method is live now – by default, in every new install of their player application on iOS or Android devices. All the time – even in Shuffle mode – and they’re working on the same system in their desktop application, too.
And that’s huge. It means Apple is now the only major streaming service not to have normalization enabled by default – apart from SoundCloud and Google Play, neither of which offer normalization yet.
And not only that, but it’s a significant upgrade in comparison to the normalization used everywhere else. By using the “loudest song method” of Album Normalization to balance albums against each other, TIDAL have ensured not only that their normalization can’t be “gamed”, and the artistic intentions of the artists are preserved, but also that their overall loudness level will comply with the AES streaming loudness recommendations.
So what ?
The momentum is building all the time. We saw the most recent signs that streaming services are really taking normalization issues seriously when Spotify reduced their playback reference level to be more in line with Apple, Pandora and YouTube earlier this year, and I’m confident the same thing will happen with these improvements by TIDAL.
After all, it’s a win-win. Using Album Normalization to the loudest song (@ -14 LUFS) gives a better user experience, is simpler and easier to understand, and is preferred by over 80% of users ! What’s not to like ?
These changes are simple, but profound. Most importantly, they overcome a major (and real) objection to normalization in general – that it shouldn’t disturb the delicate balance between songs. I’ve often heard people say “I don’t want the loudness of my songs changed”, and now it won’t be – except to keep a consistent maximum playback level from album to album.
All the streaming services care deeply about music, and high quality – despite the cynicism I sometimes see – and I’m confident they will all adopt Eelco’s recommendations in the near future.
And personally, I can’t wait.