Categories of effects in audio production

por Rafa

Hi! This is Rafa Monteiro, from Montpellier, France. This is an assignment for lesson for week 3 of “Introduction To Music Production” at Coursera.org. Today, I would like to talk to you about the categories of effects in audio production.

Last week we discussed a bit of the properties of sound, the mechanical waves that travel across the air, the earth, the water and all solid objects. In fact, sound travel across everything, with the vacuum being the only exception. Do you remember the properties of sound? They were briefly discussed along the course in many topics and videos. They are:

  • Frequency: it’s a value that represents the number of sound vibrations in a given period. We measure in Hertz (Hz), which represent the number of times a given sound will vibrate in a second interval. The higher the frequency, the higher the pitch of the sound. Humans can hear roughly between 20 Hz and 20.000 Hz, but sound can vibrate in frequencies beyond those values.
  • Amplitude: it’s a value that represents the intensity of the sound vibrations. Higher amplitude means louder sounds. It’s closely related to the dynamics of music, although they aren’t exactly the same thing. In audio production, we measure amplitude in decibels of sound pressure level, (dB SPL). Note that the decibel (dB) is not a unit of loudness. In fact, it is a logarithmic unit that express the ratio between two values of a given physical quantity. Usually, it’s power or intensity. In audio production, it measures logarithmic variations in the sound pressure of  the vibrations, with 0 dB at the threshold of human hearing.
  • Spectrum: it represents the periodic harmonic properties of a given sound. Except for pure sine wave tones, all sounds generate harmonics. Their frequencies are multiples of the fundamental frequency that generated them, with different arrangements of amplitudes for different harmonics. Some sources of sound will have louder even harmonics, for example, when others might have higher odd harmonics, or even some crazy combination of them. That spectrum (which can be seen in the spectrum analyzer of a DAW) is what gives the timbre of a sound. In essence, it’s what makes a piano sound like a piano and not like a flute.

These properties of sounds can (and are) manipulated during audio production, creating many different effects of timbre, ambience, loudness that can (and should) enhance the artistic expression of music. They are manipulated by a series of different hardwares or softwares, that we will call plugins. They got this name from the past, when all effects were produced by big electronic devices that were plugged in the mixing board. We can still see them being used in professional studios, but nowadays it’s much more common to see softwares running in DAWs doing the very same work. All you have to do is to add a plugin to a channel in the DAW Garage Band Plugin The number of effects available for use is infinite, but they all can be grouped in just three* categories. They are:

  • Dynamic effects: these effects manipulate the signal in order to change the amplitude of the sounds, changing the dynamics. That’s why they got this name. Compressors, limiters, expanders and gates fall into this category.
  • Delay Effects: these effects work on propagation. They act in two ways: manipulating the intensity of the sound (just like the dynamics), but also creating repetitions of the sound in order to give the sensation of ambience. Reverbs, delays, phasers, flangers fall into this category of effect.
  • Filter Effects: these effects work on the frequencies of the sound. They can manipulate fundamental frequencies as well as the harmonics to alter the pitch and timbre of the sounds. Pass filters, Equalizers (graphic of parametric), envelop filters, pitch shifters fall into this category.

It’s important to understand these categories of effects because it’s only possible to work with them understanding their logic and how do they work on the sound properties. Again, there are billions of different plugins available in the market, both in hardware, software or a mix of the two. They range from the most simple compressor with a button or two to the very complicated effects that mix two or all the three categories in a single unit that can create very crazy sounds. All in different sizes, prices and quality.

Many, many buttons! O.O

They might appear menacing and confusing with a lot of buttons and knobs, but they all have their logic. All becomes clear once one understand it.

*I like to think that Distortions and Boosts fall into a “fourth” category, even though they work like other Dynamic effects, by affecting the amplitude of the sound through manipulation of the audio signal. Their electronic design and circuits are very similar, but they have a totally different purpose. Boosts are usually meant to add color and warmth to the signal (pretty much like the pre amp does) and distortions are used to change the timbre of an instrument. They aren’t used the same way a compressor or gate would be used.

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