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Mixing and Processing Audio - Coggle Diagram
Mixing and Processing Audio
Levels, Pan, and Automation
Mixing
Levels
Levels refer to the volume levels, each track relative to each other.
Everything is relative and different sounds cut through differently, it all depends on context and there's no substitute for using your ears.
When setting the faders remember good gain staging practices. It's usually better to turn down sounds that are too loud instead of turning up sounds that are too quiet because sounds that are too loud can clip.
When you mix sounds together the mix will be louder than any individual sound by itself.
If the individual tracks are fairly loud, then mixing them together might exceed the limit and cause distortion.
When mixing, think of what needs to be quieter instead of what needs to be louder. That way, you won't run out of dynamic range and you'll avoid clipping distortion.
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Panning
Panning refers to where each track is placed in the speakers or headphones, left, right, or in-between.
Pan is short for panorama. Audio panning lets you move sounds around between the left and right sides.
Stereo audio always has two tracks, one for left and one for right. Hearing panning requires listening in stereo.
Rather than recording each instrument or vocal in stereo individual tracks are usually recorded in mono and then panned so that the mix as a whole has a stereo image.
There are three factors to making good panning decisions.
One-ear compatibility, mono compatibility, and bass management.
The only way to be sure everyone can always hear the most important elements is to pan those elements at, or near, the center so they appear in both ears.
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Panning means moving that single source around in the stereo field.
Automation
Lets us create changes over time to the volume, panning and other aspects of the mix.
Automation means the computer moves faders and other controls for you over the timeline of your project according to a plan that you create. Automation is what lets you control the mix at every moment of the song.
Getting the levels balanced just right is the most important aspect of the mix.
Monitoring Levels While Mixing
When mixing audio, we need to be aware of how the mix comes across at different listening sizes, that is, volumes.
The listening volume, or more precisely, the monitoring level makes a big difference in how we hear while mixing, and therefore, which mix choices we make.
Part of that is how the acoustic personality of a room, good or bad, becomes stronger at higher levels.
At low volumes, our ears are less sensitive to bass and treble frequencies.
When you turn up the volume, the bass and treble seem to get louder in comparison to the mid-range.
And when you turn down the level, the mid-range becomes, relatively, more dominant again.
To comply with the standard, an engineer sets the listening level so that a test signal, played at -20 dB, full scale, sounds at 83 dB SPL acoustically.
Most commercial music mixes are victims of the loudness war. That is, they're dynamically compressed, peak limited, and clipped so that their average level is - 8 dBFS.
Lower the level of those compressed tracks until the average is at about -20 dBFS.
Keep checking different listening levels.
Partials, Harmonics, and Equalization (EQ)
Here's a graph of amplitude versus frequency. It's called a spectrum analyzer. And it tells us which parts of the frequency spectrum.
Every sound, no matter how complex, is made up of ingredients of sine waves at different amplitudes, frequencies, and timings or phases constantly coming and going.
On the spectrum analyzer, there's a pattern of equally spaced sine wave ingredients at multiples. 100, 200, 300, 400, 500, and so on. The mathematical relationship of those ingredients is what makes the combined sound wave consistent and melodic.
Each ingredient frequency within a sound is called a partial. We also call the lowest partial the fundamental frequency, and all these higher partials harmonics, or overtones.
The fundamental frequency determines the overall pitch of the sound, and the tone, or shape of the waveform, is influenced by the other partials. That is, the harmonics or overtones.
All of the partials are exact multiples of the fundamental, so, they fit within a repeating pattern.
Those mathematically related partials are called harmonic partials. Some sounds have non-harmonic partials, which are not mathematically related to the fundamental frequency.
The recipe of partials that make up a sound determine its waveform shape, and vice versa.
So many partials are coming and going all the time that our visual tools are less useful for seeing exact partials and more useful just to watch the overall trends.
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Types of EQ Components
Equalization, or EQ for short, alters the relative amplitude of different frequency ranges.
Parametric equalizer which gives us a lot of control over the sound with several different EQ tools
high pass and low pass filters
high shelves and low shelves
peak notch filters.
Digital parametric EQs are great because they visually show how the amplitude of certain frequencies are being adjusted within a sound.
Wherever the curve goes up or down from zero, it means partials in the sound at those frequencies are turned up or down that much in amplitude.
Most of the tools in the EQ toolbox create specific shapes in the curve.
First, we have the low pass and high pass filters.
The low pass let's low frequencies pass through and progressively cuts the highs,
The high pass let's the highs pass through and cuts the lows, which is useful to get rid of low rumbling noise.
Cutoff frequency is where the roll off begins.
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Compression and Other Dynamic Processing
One meaning is data compression. Making a file take up less computer space.
Let's define dynamic range compression by describing the tool that does it. The compressor.
The goal is to reduce the sound's dynamic range, that is compress that range.
The Dynamic Range of a sound refers to how different it's quietest and loudest moments are from each other. So, a sound with very loud and very quiet moments has a wide dynamic range, and a sound that stays fairly near the same loudness has a narrow dynamic range.
The compressor is probably the most well-known member of a family of audio tools called Dynamic Processors which are used to manipulate the dynamic range of sounds.
The four main types of dynamic processors are the Compressor, the Limiter, the Expander and the Gate or Noise Gate.
The expander and the gate both increase the dynamic range of a signal, while the compressor and the limiter both decrease it.
The compressor and the expander both generally affect the signal in more subtle ways while the limiter and the gate both have more drastic effects.
There's a parameter called the Threshold which refers to a specific volume level. The difference between the four processors is based on how they behave regarding the threshold.
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Four Types of Dynamic Processors
We can define each dynamic processor in terms of two parameters
Threshold
The threshold is the volume level the processor is always watching to see if the signal's amplitude crosses it.
Ratio
The ratio is a mathematical ratio like two to one, one to two, three to one, ten to one, and so on.
A compressor kicks in whenever the signal goes above the threshold. And then the ratio determines how far the compressor turns it down in response.
When the input signal is below the threshold the compressor goes back to neutral volume and leaves the sound alone.
Most compressors have a gain-reduction meter that moves from right to left to show how far the processor is turning down the signal.
Many processors also have a graph like this called a transfer function. The input level is on the X axis and output level is on the Y axis.
The term limiter can also simply mean a compressor with a very high ratio because a compressor with a ratio of around ten to one or higher acts basically as a limiter.
The usual kind of expander, a downward expander, watches for when the signal is quieter than the threshold.
If the signal drops below the threshold though, the expander uses the ratio to figure out how much to turn down the signal even more.
If the signal is above the threshold, the expander leaves it alone.
Just as a limiter is like an extreme compressor, a gate is like an extreme expander. Setting an expansion ratio of one to infinity means that the expander is now a gate.
Attack, Release, and Knee Parameters in Dynamic Processors
Time
Dynamic processors don't operate instantly. If they did, they would distort the waveform's shape instead of responding intelligently to volume changes.
In order to sound natural, dynamic processors have parameters to adjust their reaction times. These are the attack and release parameters.
On a compressor, the attack time sets how quickly the sound is turned down once it exceeds the threshold.
Attack times are generally measured in milliseconds, or even microseconds.
And the release time sets how quickly the compressor lets go and brings the volume back to normal when the input signal falls below the threshold.
Release times tend to be longer. Because sounds often fade away more slowly. So, release times are usually measured in milliseconds or sometimes full seconds.
A compressor with a very short attack and medium release smooth out the drum sounds. A longer attack and release makes the transient cut through the drum sound.
A compressor can sound very different depending on the attack and release times.
Attack and release work exactly the same on a limiter as they do on a compressor. Since a limiter is basically a very high ratio compressor.
No matter which dynamic processor you're using, attack always effects sounds louder than the threshold, and release always effects sounds quieter than the threshold.
Many dynamic processors, especially compressors, let you set a parameter called Knee, ranging from hard to soft.
Soft knee means that instead of the threshold being a strict line, there's a gradual transition.
Hard knee can be used more easily as an effect, and to have tighter control over the exact volume levels.
Most dynamic processors let you set up what's called a sidechain. The processor will watch the sidechain signal and compare it to the threshold but then, actually control the volume of the main signal.
One easy-to-hear example is to create a pumping effect.
Sidechains can also be used in spoken word recordings to do what's called ducking.
Put a compressor on a background music track, then set the sidechain to listen for when the announcer is speaking, so that the background music gets quieter whenever someone is talking.
Reverb, Echo, and Delay
These three are related because they all involve copies of a sound repeated over time, which gives the sound a sense of space.
Reverb
Reverb happens physically in the acoustic domain. Reverb can also mean a simulation of acoustic reverberation, such as a plug-in in a DAW.
Reverb begins when sound hits a surface and a copy or echo bounces back.
The original sound continues on its way, hitting other surfaces and creating other echoes. The echoes made from those surfaces then bounce off still more surfaces, splitting and multiplying.
The result is an uncountable number of echoes of the original sound, all blurring together into reverb.
Various surfaces absorb or reflect different frequencies in different amounts. So each echo is EQ'd in the acoustic domain. The shape, size, and materials of the surfaces in the environment determine the sonic character of the reverb.
Whenever you record a sound, you're also recording the reverb of the space it's in. So record in a space where you like the sound of the room. Rooms with a lot of reverberation are referred to as live sounding.
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Echo and Delay
To refer to a single delayed copy of a sound, usually created by bouncing off a surface, I've used the term, echo.
to refer to an audio effect of individual, countable repetitions of a sound, I usually say delay.
Engineers would then set up a mixing console to send one track, or a mix of tracks, into the spare tape recorder. The delayed output of the tape machine would come back into the mix on its own track, creating a single echo effect called a slapback.
Then, by sending just a bit of the echo sound back into the tape recorder again, engineers would create a controlled feedback loop which makes repeating echos
There are plug-ins that let you specify the timing, volume, EQ, and other aspects of a couple dozen or more delays. This lets you create everything from simple slapback to more complex echoes that are almost like reverb or even, turn a sound into an entire moving beat.
Echo and delay are also the foundation of modulation effects, like chorus and flanger.
Characteristics of Analog and Digital
Many audio interfaces like this one allow multiple separate audio streams to flow into and out of the computer, converting them from analog to digital or back as appropriate.
You can set up custom signal paths in your DAW to take advantage of this and send some tracks to analog processors and others to digital plugins in the DAW.
The sound you get depends less on whether the gear is digital or analog and more on how you use it.
Analog effect processing has the chance of introducing analog problems like unpleasant or unwanted distortion, noise and hum.
Now analog recording media like tape and vinyl alters the sound with subtle distortion which adds a character that digital recording lacks. Sometimes this is called euphonic, meaning good sounding distortion.
Digital effect processing has the chance of introducing digital problems like aliasing, clipping or quantization distortion.
High-quality digital recording is essentially neutral, it doesn't significantly change the sound. Because of this you can even combine the two to get the best of both worlds.
All of that said, common myths about digital audio necessarily sounding less warm or less faithful to the original recording than analog are mostly based on misunderstanding.
Digital recording captures sound over a wider frequency range and dynamic range than analog recordings and does so without significantly coloring the sound.
Even standard CD-quality digital audio captures frequencies that exceed the bounds of human hearing.
