What Is Sibilance In Audio And How To Avoid Or Remove It

The spoken word, in our case English, is probably the most important and extensively researched "instrument" in the recording industry. Hardware and software have been specifically developed to allow vocals to be recorded in the most accurate way possible.

Ironically some of the sounds we produce while speaking or singing,  are the cause of some of the biggest headaches during the recording process. The two main culprits here are the plosive sounds and sibilant consonants our mouths produce. 

The plosive sounds we make with consonants like the P's and B's  cause unpleasant popping distortions in the recording. This led to the repositioning of the mouth in front of the microphone, as well the popular pop filter we see in front of microphones in so many studios, to deal with the issue. 

The second big problem is the vocal sibilance that is responsible for some serious recording issues. But what exactly is sibilance?

Sibilance is the unpleasant distortion and harshness in a sound, often caused by the overemphasis of consonant syllables (for example T, S and Z) during a vocal performance. This results in the unwanted "hissing" or "popping" sound in a recording that can negatively impact an audio track.

There are a variety of ways to prevent vocal sibilance, but we first need to better understand exactly how it works before we can look at ways of controlling it. 

Why Do Vocal Sibilance Occur

Using consonants like T's, S's and Z's when communicating verbally, is part of everyday vocal conversations and discussions. It occurs naturally during vocal communication and normally never sounds unnatural or out of place in almost any situation.

However, the problem occurs when these sounds are perceived or captured by recording devices which have a much smaller dynamic range than that our ears are able to perceive.

When too much emphasis is put on pronouncing these syballic consonants, especially in the upper mid-range frequencies, the dynamic range of these sounds often exceed the capabilities of the recording equipment.

As a result, these sounds that fall outside the dynamic of the recording device, get "clipped" (abruptly cut-off) resulting in the familiar and unpleasant hissing or popping sound. 

It should be noted that this not an indication of an vocal problem from the performer's (speaker or singer) side. Trying to change the way in which a vocalist perform to address the issue will be a very bad idea, as you will be interfering with the style and uniqueness of the artist's voice.

This simple discrepancy between our vocal range and the that which we are able to record, should and can be addressed in a different way.

How To Prevent Vocal Sibilance

The are 2 ways of getting rid of vocal sibilance. The one is during the recording process and the second while doing your mixing.

You know the saying, "prevention is better than cure". Well this is very true in the case of eliminating sibilance. Addressing the issue during the recording stage is much easier and more effective than trying to eliminate it later on while mixing.

Lets take a look at the 2 different approaches:

1) Eliminating Sibilance While Recording

The first and easiest way of addressing the effect of vocal sibilance, is by re-positioning the microphone. By increasing the distance from your microphone to your mouth, you allow the the peak volume of your sound to die down a bit before reaching the microphone, decreasing the effect of sibilance.

By also placing the microphone slightly to the side of your mouth at the same time, the full force of the sound produced by your mouth is also not directed straight at the microphone, which can drastically further reduce this sound distortion.

By choosing the right microphone for a specific type of sound, you will be able to completely eliminate the problem. Although the condenser microphone is normally the microphone of choice for vocal performance, it's extremely sensitive diaphragm make it very susceptible to vocal sibilance. Making use of a less sensitive microphone like a  dynamic microphone  will reduce the harshness of the sound and create a more pleasant listening experience without any sibilance impacting the sound quality.  

(Please note that using a pop filter will not help in the case of vocal sibilance. These filters are designed to effectively deal with plosive sounds produced by P's and B's. The high-pitch sounds from consonants like T's, S's and Z's will not be effectively addressed by pop filters.)

2) Eliminating Sibilance While Mixing

De-essing is one of the most widely used techniques employed by your DAW Software during the mixing stage to deal with vocal sibilance on a recording. (Simply put, de-essing is making use of a combination of compression, equalization and gain reduction to eliminate sibilance.)

It comes in the form of third-party plugins, or many DAW software has it build-in as part of their compression functions. The fact that the type of sibilance can vary from one source to another, means you sometimes have to do some playing around with the settings to get the right result.

You can also manually reduce the effect of sibilance by using the fader on your software. This means you have to go through the whole recording and manually reduce each instance where sibilance is found. This can be an extremely time-consuming and cumbersome task.

Conclusion

As we have seen in this article, vocal sibilance is not a fault or mistake on the vocalist part. It is simply a natural sound we use while communicating verbally (talking or singing), which pitch and volume can fall outside the dynamic range of a recording device, resulting in this harsh unpleasant sound.

You now also know that there are a variety of ways to limit or completely remove sibilance, on both the recording and mixing side.

And finally we now know that preventing vocal sibilance from happening in the first place, is much more effective than trying to deal with it during the mixing stage.

As always, feel free to leave me any comments or suggestions you may have, and I will respond and try and get to them as soon as I can.

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Catch you in the next article and happy recording!

Wessel