Compressors and Gates
“Compressors and limiters are used to reduce dynamic range — the span between the softest and loudest sounds. Using compression can make your tracks sound more polished by controlling maximum levels and maintaining higher average loudness.”
Some of the basic elements of compression are as follows:
Threshold
The threshold sets the level at which the compression kicks in. Only when any signal input exceeds the set threshold will the signal be compressed. Once the level is set, only signal peaks that exceed this level will be compressed.
Knee
The knee affects how the compressor reacts to and transitions between the compressed and non-compressed versions of audio signals running through it. A hard knee immediately compresses the signal. A soft knee on the other hand gradually attenuates the signal before and after the threshold to allow for a more gradual sweep into the compression. A soft knee is more useful for things like vocals and melodic instruments.
Ratio
The ratio is how much compression is applied. A ratio of 5:1 means that for every 5dB (5.0) of increased volume, the compressor will only allow 1dB (1). A ratio of 1:1 means that no compression is taking place, whereas a ratio of 20:1 or greater means the compressor is acting as a limiter; all signal peaks that exceed the threshold are cut off.
Make-Up Gain
Compressors reduce the level of the loudest signals, which means that you end up with a quieter signal after compression. When you add make up gain, it basically increases the volume of the audio by increasing the smaller frequencies to the the same level as the higher levels were previously. Now the level of the audio shouldn’t be affected.
Attack
The attack time is how quickly the compressor takes to kick in. Faster attack times tend to distort audio tracks due to the quick progression of the lower frequencies. Slower attack times help to smooth out the audio transition once the compressor has kicked in.
Release
The release time serves the same purpose of the attack but relates to how quickly the compressor stops after the signal falls below the threshold. Like the attack time, smaller the release times cause clipped, unnatural sounding audio. If the release time is too slow, it will mean that some of the signal is still being affected by the compressor.
“Loudness meters are essential tools used in music production, mixing and mastering. A loudness meter can analyse, measure, and monitor audio levels in real-time for various purposes.”
LUFS references Loudness Units to full scale (i.e., the maximum level a system can handle). Basically, Loudness Units are used in the process of expressing the level of the perceived volume by analysing the average level over time. If two pieces of audio have the same LUFS should sound the same. The highest point the analog signal reaches is called the true peak while the highest digital sample is called the sample peak. As a digital signal has to be converted into an analogue one to be heard, the true peak is a
much more sensible measurement for the peak level of a waveform.
References
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McClellan, R. (2015). True Peak Detection. [online] iZotope Tech Blog. Available at: https://techblog.izotope.com/2015/08/24/true-peak-detection/ [Accessed 14 Nov. 2019].
PQ, R. (2019). What Are Loudness Meters and Why It Matters | Icon Collective. [online] Icon Collective College Of Music. Available at: https://iconcollective.edu/loudness-meters/ [Accessed 14 Nov. 2019].
Pro Audio Files. (2016). What is Compressor Makeup Gain? — Pro Audio Files. [online] Available at: https://theproaudiofiles.com/video/compressor-makeup-gain/ [Accessed 12 Nov. 2019].
Sweetwater. (1997). Attack. [online] Available at: https://www.sweetwater.com/insync/attack/ [Accessed 12 Nov. 2019].
Sweetwater. (2018). [online] Available at: https://www.sweetwater.com/insync/what-is-lufs-and-why-should-i-care/ [Accessed 14 Nov. 2019].
Uaudio.com. (2018). Audio Compression Basics | Universal Audio. [online] Available at: https://www.uaudio.com/blog/audio-compression-basics/ [Accessed 11 Nov. 2019].
Vincent, S. (2012). The Beginner’s Guide to Compression. [online] Music & Audio Envato Tuts+. Available at: https://music.tutsplus.com/tutorials/the-beginners-guide-to-compression--audio-953 [Accessed 11 Nov. 2019].