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In this first installment of the Foundations of Audio series, author Brian Lee White shows how to improve the sound of a mix with compressors, limiters, gates, de-essers, and other dynamic processors. The course explains the fundamentals of sound waves, and amplitude, explores common compressor controls, and shows how to eliminate unwanted noise using gates and expanders. The course also demonstrates best practices in compression and limiting in a variety of audio applications and covers sculpting the attack and decay of individual notes with transient shapers and applying frequency specific dynamics control with multiband compressors. Exercise files accompany the course and include special Get in the Mix session files.
Dynamic range is the difference between two extremes. In audio, dynamic range represents the ratio between the loudest and softest signal being produced over any given interval. Every day we experience this concept of dynamic range almost constantly across all of our senses. And as humans, we're quite adept at recognizing it: light and dark, hot and cold, hard and soft, and for the purpose of this course, loud and quiet. A sound's amplitude directly correlates with its loudness.
But what is loud? What is quiet? Is a concert loud? Is a library quiet? That depends. But I can assure you, if you walked out of a library and into a rock concert, you would have a pretty good idea of the difference in loudness between the two spaces. Loudness in our minds is not finite. It's all about perception. The key thing to understand is that we need both ends of the spectrum to fully evaluate what's loud and what's quiet. The distance between these extremes is what we call dynamic range.
For example, if you heard a book fall off a desk in a library, it would startle you. This is because the difference between the sound of the book falling in a library versus the library's quiet environment is fairly extreme. This same effect is used by movie sound designers. Ever jump out of your seat from a loud explosion? At its limits, the human ear can experience roughly 120 dBs of dynamic range, with 0 dB being imperceptible and 120 reaching the threshold of pain, although much of our day-to-day experience of dynamic range exists in a much narrower space.
For example, a modern pop mix may only have around 8 to 10 dB of dynamic range between the peak and average amplitude values over the entire song, while a modern film may have around 20 dBs of peak-to-average dynamic range, which is why you would be more likely to jump out of your seat at a movie theater during a loud explosion than you would be listening to a song in your car. Let's listen to some examples. This first example has a wide dynamic range. Imagine a quiet park interrupted by car horns and sirens.
(ambient sound) (car honking) (sirens) Now, here's an example of reduced dynamic range, a fully mastered pop mix. (music playing) Unlike the quiet park scene that's interrupted by loud horns and sirens, the pop mix maintains the same perceived loudness, thus exhibiting a much narrower dynamic range.
As a side note, 16-bit recording systems offer 96 dBs of dynamic range. In comparison, 24-bit recording offers a much wider range of 144 dBs, exceeding the range of human perception, which is generally accepted to be around 120 dBs. Because of this, 24-bit recordings can accommodate a wider range of amplitude values before digital clipping. Now that we understand the basic concept of dynamic range, we can begin to harness the power of dynamics processors to control it.
Just as we can measure the change in perceived loudness of quiet dialogue in a film to a loud bomb-explosion sound effect, we can also measure the dynamics over shorter periods of time, like the volume differences in phrases of a vocal track from line to line or the amplitude curve of the crack of a single snare hit. And since we can measure these dynamic range relationships, we can change them if they aren't working for us. We'll do just that using dynamics processors.
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