The Art & Science of Sound

Dynamic Compression and the Loudness Wars

By Jack Sharkey, November 20, 2018


Years ago I had a neighbor. I don't think he worked or anything. He basically just sat by his pool from mid-May to early September drinking beer and listening to music. He was very popular, because it seemed like people from miles around would arrive at his house at 4:00PM on Friday and stay there until 10:00PM on Sunday. I’m not complaining or anything – all of this entertainment was non-stop and didn't cost me a dime.


After a couple of years of this however, I dared to ask him to cut back on the volume a little, and even though he was fairly drunk, he was able to give me this technical explanation about why the music was so loud:

"You know, on the iPod, how sometimes some songs are louder than others, and then sometimes they're really quiet? There's nothing I can do about that." 

He didn't exactly address my concerns, but he did raise an interesting point. There's a hidden reason his vast musical library was so difficult for him to operate and you can pretty much thank your favorite radio DJ and record label pitchman for that.

Back in the days of the original mp3, the 45rpm single, radio stations would get stacks and stacks of new material on a weekly basis. The problem label pitchmen faced was how to get their horrible song noticed before everybody else's horrible song. And the best way to get a record to jump out at a program director? Make it louder than every other record. Hence, the loudness wars. Once the CD came along in the late 80s, there was virtually no limit to how loud a song could be – even if it was just an acoustic guitar and a lone singer.

Music produced in 2005, was on average, 5dB louder than music produced in 1969 (Sound On Sound magazine: Dynamic Range & The Loudness War - Sept 2011). However, as with everything musical, there is no single explanation for the loudness war.

On vinyl, there is only so much volume you can master onto a disk before it starts to make the needle jump out of the groove. This is especially true with 45's because their grooves are so much shallower than the grooves on an LP. On vinyl, my Slade LPs were way the hell louder than my America LPs, but on CD, America and Slade pretty much play at the same volume, and this disrupts the harmony of the cosmos.

With digital replication, there are no physical volume constraints, so with the CD came an explosion of source volume. The problem with volume, as all of you who spend the holidays with your families can attest, is that it is fatiguing. Our ears tire quickly when confronted with a constant volume with few quiet spots.

Compression: It's How Music Gets Made Louder 

Dynamic Compression should not be confused with Data Compression, the other type of compression that ruins music.

Basically, Dynamic Compression (DRC for Dynamic Range Compression) quiets the loud parts and amplifies the quiet parts, making the overall volume more consistent. This is accomplished by setting a threshold and then raising or lowering (respectively) any signal that crosses that threshold.

Downward Compression reduces the level of a signal that is louder than the set threshold.

Upward Compression increases the level of a signal that is quieter than the set threshold.

Theoretically you can end up with a mastered song that does not vary in amplitude at all, regardless of its arrangement, but compressed music can still have dynamics. Music recorded properly by people who know how to layer and work with dynamic compression are proof of that, but compression isn't the only culprit. When we talk about the loudness wars and listener fatigue, we also need to consider the role limiters play.

The Difference Between Compressing and Limiting

A dynamic compressor slowly and smoothly limits a signal that crosses a set threshold. Compressors change the dynamic range of a signal based on the ratio they are set for. A ratio of 4:1 means that a 4dB increase in volume at the input results in a 1dB increase of volume at the output. A ratio of 10:1 means a 10dB increase in volume is output at 1dB. There are a lot of other factors with compressors, but they are way beyond the scope of this piece.

A limiter is like a really angry compressor. A compressor can be set to turn on slowly and turn off quickly to make the compression transition less noticeable, whereas a limiter just clamps on and cuts the signal back (soft clipping). If driven too hard, limiters will hard clip a signal, making it sound very harsh to listen to.

Harshness + volume = listener fatigue. Listener fatigue = less musical enjoyment.

I Knew It! Technology Has Destroyed Music! 

Yes. And No.

"I don't know anybody who's made a record that sounds decent in the past 20 years. You listen to these modern records, they're atrocious, they have sound all over them. There's no definition of nothing, no vocal, no nothing, just like ... static." - Bob Dylan, 2006.

We can argue all we want about the state of music today, but the argument is nothing new. 

Maybe the Very Nature of Music Today Makes It Seem Louder? 

Possibly. Let's listen to a drummer from the Classic Rock era who is thought of as loud and punishing, but who, in reality had a touch equal to that of the great jazz drummers. Warning: Explicit.

As you listen to this, take notice of the spaces between the notes. The air and space are what gives his drumming – and therefore his band's music – the dynamics it has. He hits hard or lays back depending on the demands of the arrangement of the song. 

Now let's listen to Roar by Katy Perry, an excellent representation of popular music in the twenty-teens.

From a pure songwriting point-of-view, this is a great song – you can’t deny the hook. Unfortunately, it's a boring production of a great song. I couldn't find an isolated drum track (presumably because the computer that made the track is still collecting royalties) but listen to the drums and nothing else: dull, lifeless, with no real spaces or air between notes. There are no dynamics. Couple that with the synth bass which really just fills the space beneath the doubled (tripled) super-compressed vocal track and you have a song that could be stirring and moving but is instead just flaccid and dull. Our ears are straining for air and space, so we perceive the lack thereof as flat and fatiguing.

Is it possible we are to blame for the perceived loudness in music because of what we buy and the way we listen? I submit that we, the music fan, are partially to blame for the very things we hate in music today. Katy is cute and the camera loves her, and on my nineteen dollar earbuds I don't need a lot more than that, but as a musical statement played on the quality equipment our ears deserve? Meh.

So, the truth, as usual, is somewhere in between music is horrible today and no it's not. We listen to music differently than we did thirty years ago, so that must be taken into consideration when we talk about the loudness wars. We also listen to different music as well.

From a technical standpoint (not an artistic one), compression (and limiting) changes the original source signal. That may be the artist's goal and when it is, that's fine (Nine Inch Nails come to mind), but when an artist's goal was to perform a piece with space and air in between the notes, then the modern way we produce music gets in the way.

When the majority of music is consumed on computer speakers and earbuds, the dynamic range becomes less important. In modern music, the guitar and keyboards (organ and piano) and complex arrangements and soundstages have mostly taken a backseat to driving bass and repetitive melodic structures. This is no accident: Music is not worse today because it is louder per se, but there is no argument that music that is less dynamic is generally more popular right now. Our ears have become conditioned to the way we listen to what we listen to, and maybe the recording industry is just responding to that. It's a chicken or egg argument with no simple answer.

The science cannot be disputed: Overly compressed music loses the human component that makes music enjoyable in the first place. Overly compressed music becomes fatiguing and annoying to listen to so our listening habits reflect that – why sit and listen to something that’s going to physically annoy you after ten minutes?

Take heart – there is plenty of music out there (new and old) produced with dynamic range in mind, the loudness wars have only made some if it harder to find.

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