SEPTEMBER 27, 2023

What is Spectral De-Essing?

pro tools session with m-de-esser and rx showing spectrogram

In mixing, we always strive to create something exciting that moves the hearts of people, that connects with them. It’s a highly creative task, but it can also be very technical. No wonder we often use the term "mixing engineer" to emphasize the technical side of the process.

When working on a song or any other type of production, we try to make audio sources sound their best. After all, how can we think creatively when there is an annoying sound getting in the way? To effectively eliminate such issues, we need to be able to identify them, understand what they are, and know what tools we can use to remove them.

Of course, not all humans perceive sounds exactly the same way. There's a degree of subjectivity regarding what can be considered a "bad sound." However, the human auditory system generally reacts similarly to especially annoying sounds, such as harsh sibilant sounds. These are the types of sounds that almost everybody considers unpleasant. It's very easy to identify them once you hear those sharp "s" or "sh" sounds—you'll probably want to do something about them.

pro tools session with dyn3 de-esser

There are many tools that can help you do that. Thankfully, we live in a digital world with an abundance of tools aimed at dealing specifically with sibilance. You can use dynamic EQ, multiband compression, dedicated de-essers, or simply lower the volume of sibilant sounds. All these tools are perfectly fine and capable of dealing with sibilance. Some of them require more manual labor like editing, while others are more automated, like a de-esser plugin. However, in some cases, they may not achieve the level of audio quality you desire.

That's when you might want to start looking into automated plugins that intelligently analyze the audio spectrum and make adjustments based on very advanced algorithms.

Understanding Spectral Shaping

So, what is exactly spectral shaping? Spectral shaping is the art of manipulating the frequency content of an audio signal to achieve desired tonal characteristics, balance, and clarity. Think of it as a sculptor's chisel for sound, capable of enhancing specific frequency ranges, attenuating unwanted resonances, and creating entirely new timbral textures. This process involves working in the frequency domain, where audio signals are analyzed and modified. This can involve various techniques to modify the spectral characteristics of the sound, such as boosting or cutting specific frequencies, altering the balance between different frequency components, or even creating entirely new spectral features.

Of course, all engineers shape the spectrum of audio sources within the mix just by applying an EQ or using multiband compression. Therefore, it's important to add that when we talk about spectral shaping, most of the time we are referring to plugins that automatically manipulate the spectrum by intelligently identifying frequencies or resonances and altering them dynamically. By relying on such advanced and intelligent algorithms, we greatly decrease the amount of time we must spend battling those sibilant sounds, and we get better, more transparent results. Such plugins can be more precise, removing only what needs to be removed, unlike other processes that can be too heavy-handed when a more delicate approach is needed.

The Inner Workings of Spectral Shaping

So, how does this process work exactly? Well, it can vary from plugin to plugin, but let's try to go through a general concept:

  1. Signal Analysis: The plugin starts by analyzing the frequency content of the signal.
  2. Detection: If the plugin's main goal is to remove resonances, it aims to identify problematic frequencies or resonances by looking for patterns in certain frequency ranges.
  3. Dynamic Adjustment: Once the plugin identifies the issues, it applies dynamic adjustments to the signal. In many cases, plugins change the amplitude of these resonances, much like a very precise multiband compressor or a dynamic EQ. Whatever technique is used to adjust the audio spectrum, adjustments are not static and are made in real-time.

The significant advantage of these plugins lies in their adaptive nature. They can adjust their processing with high precision based on the incoming signal. They continuously analyze the audio and adjust their behavior accordingly. Another key achievement of these plugins is transparency. The adjustments are designed to maintain the natural character of the audio while addressing the specific issues they target. The algorithms aim to enhance the sound without introducing noticeable changes or improving audio in ways that cannot be achieved with traditional tools.

Comparing Spectral De-Essing and Regular De-essing

pro tools session with m-de-esser

If you compare a regular de-esser with one employing spectral shaping, you'll notice that a spectral de-esser can maintain quality even at extreme settings. Techivation’s M-De-esser is a prime example, as pushing every setting to the maximum may not result in lisping, unlike with regular de-essers, where this can occur even with very mild settings.

This distinction arises because regular de-essers function essentially as compressors, and the artifacts generated by compression can adversely affect the sound, particularly with sibilant sounds. Spectral shaping, on the other hand, employs an algorithm that intelligently determines which part of the signal and how much should be controlled, focusing only on the most crucial areas, rendering the effect more transparent.

Another advantage of spectral de-essers like M-De-esser is that they not only help control sibilance but also enhance the spectrum of audio sources, stabilizing and improving it. For instance, the preset “Warmer Vox” not only eliminates sibilance but also generally enhances the sound of vocal recordings, making them sound as if they were recorded with a better microphone. This feature can be particularly beneficial in situations where a microphone was too bright for a vocalist.

Spectral shaping not only helps us achieve better results with day-to-day mixing tasks but also offers additional benefits, elevating the overall quality of tracks. It's akin to the effect you sometimes get from running signals through certain pieces of analog gear to achieve a better sound. Analog gear has this almost magical ability to uncover pleasing aspects of audio signals, bringing them to the forefront. Similarly, spectral shaping helps remove unpleasant frequencies, revealing the best in your tracks. While the technical process may differ, the end result is smoother and more pleasing sound.

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  • Gleb Karpovich

    Gleb is an engineer with over 10 years of experience. In addition to engineering, Gleb played in bands as a guitarist, taught mixing, and worked as a marketing manager with several pro audio companies.

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