2011-11-29

Sound, dynamics, and such

This morning I came across a newspaper article trying to describe difference between current and former mastering practices for records.  And of course with generous helpings of confusion.  Most records today are mastered in a way that leaves very little dynamics.  For those of you not familiar with what "dynamics" means in this context;  high dynamics means that there is a bigger difference between the loud and the silent parts of a recording.

There are lots of tricks to boost silent parts and dampen the loud parts, but the most important tool in the arsenal to accomplish this is various forms of compressors.  For more information on dynamic compressors the article on Wikipedia might be helpful.

While over-zealous use of compressors makes the sound somewhat dull and uninteresting it might be useful to point out why this is done.  It is an adaptation to make recordings sound a bit better in challenging listening conditions.  Most of us do the majority of our listening (to music and other content) on crappy earbuds in noisy environments.  By compressing the dynamic range you don't have to ride the volume controls on your device when you are listening to music in your car, for instance.

This is nothing new, but it is, and has always been, a balancing act.  There have always been devices and listening conditions where dynamics is a challenge.  For instance, a lot of mastering engineers will have multiple sets of loudspeakers, some of which are rubbish, to test their settings.  In an interview I read years ago, one mastering engineer pointed out that he used the crappy stereo in his car to test his work.  If it worked there, and on his high end studio monitors, it was probably a good final master.

As a consumer I've long wished for compressors to become part of the player -- so that you can choose to what degree content should have its dynamic range compressed.  For instance, if I am listening to a record at home, on a decent'ish stereo, I want the full dynamic range and as little compression as possible.  However, if I am in my car, I might want the dynamic range to be as narrow as possible so the faint parts are not drowned out by noise and the loud parts do not burst my eardrums.

Some movies have awful sound mixing.  The silent parts are too silent and the loud parts are too loud. If you are watching a movie in a noisy environment you end up riding the volume buttons and being annoyed.

Some devices have very simple compressors.  For instance I had a CD player years ago that had a built-in compressor.  (Generally you want to perform any compression on the digital signal, not the analog signal).  However, this is not a very wide-spread feature.

Learning how to use a mastering compressor takes time.  In fact, they can be quite complex beasts, featuring different compression parameters for different frequency bands etc.  It is going to take a while for fully automated detection of adequate compression parameters is going to sound good.  This is why I would love if the sound industry could come up with a reference model for compressors and encode the parameters into an automation track delivered with the content.  This way the consumer could turn compression on when desirable -- or even be given a control that lets the consumer decide the severity of compression.

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