Top 7 Tips To Reduce Sibilance In Microphones & Audio Mixes

Sibilance is a natural and necessary part of human speech but can be a distracting nuisance in microphone signals and audio mixes. Speech and vocal intelligibility are important, but so is a great sounding mix!

Here are the top 7 tips to reduce sibilance in your microphones:

1. Choose a microphone with a darker character
2. Distance yourself from the microphone
3. Tilt the microphone slightly off-axis
4. Place your finger or a pencil against your lips
5. Fix with a de-esser
6. Fix with equalization
7. Ride/automate the fader/levels

The first 4 have to do with the microphone and performance, while the last 3 can help to reduce sibilance in recorded audio signals and mixes

In this article, we'll describe sibilance in greater detail and then run through the 7 methods to reduce sibilance in our microphones and our mixes.

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What Is Vocal Sibilance?

Phonetic sibilance is a vocal formant known as “fricative consonant,” in which the tip or blade of the tongue is brought up near the teeth or palette, and air is pushed past the tongue. It is better known as the hissing sound. In English, sibilance happens on the consonant sounds of S, Z, Sh, and Zh (as is “leisure” – lei-zh-ure).

As we'd expect, sibilance is a necessary part of speech intelligibility. Try saying “sentences starting and stopping with sibilances” as a silly example. Without sibilance, we wouldn't be able to speak (or sing) this sentence.

When we talk about sibilance in the audio world, it's usually in a negative way. This is because vocal sibilance often causes harshness in the microphone audio signal.

Sibilance is typically in the frequency range of 5 kHz to 8 kHz (though it may occur below or above that range). When a sibilant sound hits the microphone, these frequencies are disproportionately represented in the mic signal, and the audio often becomes overly harsh-sounding.

These tricky sibilant formants can be a real headache for audio engineers and certainly for listeners if the issue isn't solved at the source or in the mix.

Fortunately, there are ways to reduce the harshness of sibilance at the source (in the microphone). If, for some reason, we have recorded audio with particularly irritating sibilance, there are ways to fix that as well.

With that being said, let's get into the top 7 tips to reduce sibilance in microphones and audio mixes!

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How To Reduce Sibilance In Microphones

A common saying in the audio industry is “get it at the source.” This means that we record the vocals (or any sound source) correctly to begin with so that we do not have to deal with altering it in the mix to have it sound right.

Before we get into it, it's important to understand that every vocalist is different. Therefore, a method that works amazingly well at mitigating the sibilance of one vocalist may fail to help with another vocalist (and vice versa).

To reiterate the methods of reducing microphone sibilance, I'll repost the first 6 tips here:

1. Choose a microphone with a darker character
2. Distance yourself from the microphone
3. Tilt the microphone slightly off-axis
4. Place your finger or a pencil against your lips

Let's discuss each of these tips in more detail.

1. Choose A Darker Microphone

Sibilance typically occurs in the frequency range of 5 kHz – 8 kHz (though it sometimes causes a disproportionate boost outside this range).

So one way to reduce sibilance is to choose a microphone with a darker colour/character. These microphones have slight dips in their sensitivity in the upper-mid and high-frequency ranges and won't be as affected by sibilance as brighter microphones.

This is, of course, at the expense of a brighter microphone audio signal. I would suggest trying this if, when working with a new vocalist, you find the vocals overly bright and the sibilance overly harsh.

Ribbon dynamic microphones naturally have gentle high-end roll-offs, which gives them a dark yet accurate frequency response.

On the other hand, FET condenser microphones sound overly accurate and often sterile (especially when they're used to record digital audio).

To learn more about coloured mics, ribbon mics, and FET mics, check out the following My New Microphone articles, respectively:
• What Are Coloured And Flat Microphone Frequency Responses?
• What Are FETs & What Is Their Role In Microphone Design?
• Dynamic Ribbon Microphones: The In-Depth Guide

2. Distance Yourself From The Microphone

Having some distance between the vocalist and the microphone is a great way to reduce the likelihood of sibilance overload.

Start by positioning the vocalist two fist-lengths away from the microphone as a rule of thumb (or rule of hand). One fist between the mic and the pop filter and the other between the pop filter and the vocalist.

To learn more about pop filters, check out my articles What Is A Microphone Pop Filter And When Should You Use One? and Best Microphone Pop Filters.

At closer distances, microphones are more sensitive to the vocals' sibilance (and plosives) and will be more easily overloaded by the vocalist.

This sibilance overloading is caused by excessive levels of upper-mid “sibilant” frequencies. By placing the microphone further from the vocalist, we give these high frequencies space to dissipate, helping to reduce their overbearing presence in the overall sound waves.

3. Tilt The Microphone Slightly Off-Axis

In addition to positioning the mic at an appropriate distance, it's also worth tilting the microphone slightly off-axis. This simple technique, like the distancing, works double-time to reduce both sibilance and plosives in the mic signal.

I personally angle studio vocal microphones downward about 15°-20°, having the primary axis of the microphone point toward the throat rather than the mouth, which is the source of sibilance of the vocalist. I usually start with this mic positioning and adjust if need be.

Other engineers will turn the mic slightly to the left or the right of the vocalist rather than tilting it down, and that's fine, too. However, I've found tilting down to be better since the vocalists tend to naturally move toward the front of the mic (if the front/primary axis is obvious).

Basically, angling the microphone will alter how the higher frequencies are captured. All microphones tend to become less directional at lower frequencies (and more directional at higher frequencies).

So tilting the mic slightly off-axis will colour the sound, lessening the top-end (see tip #1). At the same time, the sibilant energy travelling through the air will reach the diaphragm at an angle rather than straight on, further reducing the effect of “sibilant overload.”

To learn more about microphone directionality and plosives, which have been mentioned above, check out my articles The Complete Guide To Microphone Polar Patterns and Top 10 Tips For Eliminating Microphone Pops And Plosives, respectively.

4. Place Your Finger Or A Pencil Against Your Lips

This is a rather strange trick, but it actually works in practice. The “pencil trick” is primarily a method to reduce plosives in the microphone signal but, like many of the plosive-reducing techniques, also has the effect of helping lower sibilance.

By holding a pencil/pen or your finger up to your mouth, you effectively dissipate sibilant energy at the source, sending it in many different directions with less energy rather than more directly with more energy.

This reduces the impact of sibilant energy at the mic diaphragm and helps to reduce harsh sibilance in the microphone signal.

Alternatively, and this is probably easier, we could strap a pencil to the microphone's grille in front of the capsule. This would cause dissipating much closer to the diaphragm, so, in theory, it would be less effective.

However, it would likely be more effective in practice due to its stationary nature (versus the dynamic nature of physically holding a pencil up to your mouth).

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How To Reduce Sibilance In An Audio Mix

Along with “get it at the source,” another common phrase for audio engineers is “fix it in the mix.” I much rather the first saying.

Sometimes there's just no winning the battle against sibilance during recording. Fortunately, there are methods to undo the recorded harshness of sibilance in recorded audio.

Let's have a look at these methods once again:

5. Fix with a de-esser
6. Fix with equalization
7. Ride/automate the fader/levels

Let's discuss each of these tips in more detail.

5. Fix With A De-Esser

The de-esser is the holy grail of sibilance reduction in the mixing world.

De-essing is a classic compression technique to reduce vocal sibilance through audio processing. With de-essing, a compressor acts on a limited frequency band rather than the entire audio signal. As you may have guessed, this frequency band is in the sibilance range (the de-esser sidechain band is typically a thin slice of the 5-8 kHz range).

Essentially what happens is, any time the sibilance energy is too hot in the mic signal (or any audio signal being processed), the compressor reduces the gain (volume) of that signal. So any time a sibilant peak in the audio signal would occur, the gain is dropped, and the audio becomes much less harsh to the listener.

With that brief introduction, let's look at de-essers more closely. After all, they are the primary method of reducing audio sibilance, so it would be a disservice to you, the reader, if I did not take the time to explain them in detail!

The De-Esser Signal Flow

De-essers utilize a special feature available to most compressors. This feature/technique is known as sidechain compression.

Sidechain compression uses one signal to control the compressor but having the compressor act on a different signal. The most obvious form of sidechain compression I can think of is in Electronic Dance Music. The kick drum (often hitting on every quarter note) acts as a sidechain to effectively duck the synths, basses, and other instruments in the mix.

So in a de-esser, which is effectively a sidechain compressor, we have 2 signal paths:

1. The audio path: This is the full signal (whether from a microphone or not) that is subjected to the compressor's conditional gain reduction.
2. The sidechain path: This is a narrow band (in the sibilance range) of the audio path that triggers the compressor's conditional gain reduction.

All other processing aside, we'll say that the audio path is clean.

The sidechain path, however, has a rather drastic EQ applied to it. The offending sibilance frequencies are to be found within a frequency band in the sidechain path. All other frequencies are then EQed out of the sidechain signal (typically via a bandpass filter).

The compressor is then set to reduce the gain when the sidechain signal crosses a set threshold. When the threshold is set appropriately, any overly present sibilance will cause gain reduction in the audio signal, thereby reducing the harshness of the sibilance.

To learn more about compressor threshold control, check out my article Dynamic Range Compression: What Is The Threshold Control?

This user-defined frequency band in the sidechain signal makes it much easier to achieve gain reduction during heavy sibilance and only then.

It's important to note that the sidechain compression does not remove sibilance, per se. Rather, it ducks the audio signal when sibilance is high so that the harsh sound is not overpowering within the mix. The de-esser settings may be adjusted for varying amounts of gain reduction to suit the particular vocal track.

To learn more about sidechain compression, check out my article The Complete Guide To Sidechain Compression In Audio.

Preconfigured De-Essers

Sidechain compression can be a bit difficult to set up. As luck would have it, there are pre-configured de-essers on the market (often in software plug-in form).

These de-essers provide a relatively simple interface with compression settings, a peak-EQ centre-frequency control, and other adjustable parameters.

Adjust your compression settings and set your sibilance range, and you've got a great de-esser! From there, you may further tune the processing to make the vocals fit in the mix exactly as you'd like.

Note that compression, by itself on the entire audio path, is likely to worsen the sibilance of an audio signal. Squashing the harshest sibilant parts of the signal will only make them more prevalent to the listener.

De-Esser Plugins

Sidechain compression can be done with hardware compressors and equalizers but is best done, in my own opinion, through software plug-ins. The pre-configured de-esser plugins on the market now are powerful and precise enough to fulfill all your de-esser needs.

The best de-esser plugins I've had the opportunity to use are:

• Fabfilter Pro-DS (link to check the price at Plugin Boutique)
• Waves R De-Esser (link to check it out at Waves)

FabFilter and Waves Audio are both featured in My New Microphone's Top 11 Best Audio Plugin (VST/AU/AAX) Brands In The World.

How To Use A De-Esser

Let's now go over a quick checklist you can go through to get the most out of your de-esser:

1. Apply the de-esser plugin on the vocal track: it's typical to insert a de-esser plug-in at the beginner or end (or both) of the signal chain.
2. Loop a section of the vocal with particularly bad sibilance: I aim to find and loop the worst-case of sibilance and work from there. If the de-esser work on the worst sibilance, it should work on the weaker sibilance peaks. Always check the lower peaks to ensure the de-esser doesn't overdo it.
3. Set the frequency range of the sidechain path: some de-essers give you a centre frequency and Q-control to adjust the sidechain frequency band. Others give multiple controls to set the proper range. Set the sidechain range to cover the sibilant frequencies.
4. Set the threshold of the de-esser: This essentially controls the trigger-point at which a sibilant peak will cause gain reduction in the signal.
5. Set the reduction of the de-esser: This determines the amount of gain reduction that will happen when the sidechain signal exceeds the threshold.

6. Fix With Equalization

EQing the signal can help to reduce the sibilance in an audio signal similar to how a darker microphone can reduce the presence of sibilance. However, this method is not nearly as effective or transparent as a de-esser.

EQ should be applied sparingly in the sibilance range (5-8 kHz), or else the audio signal may begin to sound muddy and muffled.

That being said, a gentle high-end roll-off or even a slight dip in the sibilance range could help to bring down sibilance if it's particularly bad. Alternatively, a narrow band cut could help tremendously if the vocals have a very specific and narrow band of sibilance.

Note that much of the sibilance range overlaps with the presence range of vocals (roughly 3-6 kHz) which is often helpful in bringing vocals to the front of a dense or loud mix. All this is to say that special attention should be paid when EQing for sibilance reduction.

For more information on vocal presence in microphones, check out my article What Does “Presence” Mean In Terms Of Microphones?

To learn more about audio equalization, check out the following My New Microphone articles:
• The Complete Guide To Audio Equalization & EQ Hardware/Software
• Top 11 Best Tips For EQing Vocals

7. Ride/Automate The Fader/Levels

When done correctly, level adjusting is perhaps the most transparent method of reducing sibilance. It is also by far the most tedious.

Manually dipping the level of the vocal track when you hear an “s” is a meticulous task. It's essentially a form of manual compression, or in the case of sibilance, manual de-essing.

I personally stay away from manual tasks in professional work because they cut away into “profit hours.” However, I will manually dip levels if I have to deal with a particularly stubborn sibilance peak that cannot be taken care of with the above-listed methods.

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Related Questions

How do I reduce plosives or popping in my microphone? There are various methods to reduce plosives in mic signals. The primary method involves placing a pop filter between the vocalist and the mic. Pop filters allow sound to pass through while blocking/dissipating much of the plosive energy before it hits the mic diaphragm.

To learn more about plosive reduction, check out my in-depth article Top 10 Tips For Eliminating Microphone Pops And Plosives.

What is microphone frequency response? Microphone frequency response refers to the frequency-specific sensitivity of a specific mic. The audible range of frequencies is from 20 Hz – 20,000 Hz, and mics are designed to convert sound waves within this range into audio signals.

For everything you need to know about microphone frequency response, check out my article The Complete Guide To Microphone Frequency Response (With Mic Examples).

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