What is sibilance

Whether it’s broadcasting, music, film, or online content creation, eliminating hissing is crucial to creating high-quality audio productions and enhancing the overall impact of the media. In this article, you’ll learn everything you need to know about hissing sounds.

What is hissing?

So, what are audio sibilants? These are the “S” and “Sh” sounds in vocal recordings. They may not bother you personally, but recording vocals through microphones can make them much more pronounced, resulting in shrill and harsh vocals. For example, recording a podcast with a condenser microphone from close range can highlight these sounds.

Excessive hissing sounds make the sound harsh and unpleasant. Add to this a bad audio mix, and it can be quite painful to listen to. Why? Hissing sounds occur in the 2 kHz to 8 kHz frequency range, where our hearing is most sensitive.

Hissing is natural in speech, and we don’t notice it in normal conversations or unamplified live performances. The problem only arises when you record or amplify vocals with a microphone.

Unraveling Sibilance: Understanding Its Definition and Frequency Range

Sibilants are the hissing or sharp “s”, “sh”, “ch”, and “z” sounds produced by human speech. These sounds are characterized by high-frequency energy and sometimes sound harsh or distracting when recorded. This occurs when the airflow during speech passes through the narrow space between the tongue and the roof of the mouth, creating a turbulent sound.

Example: “She sells seashells on the seashore.”

In this sentence, the sibilant sounds are:

• The “s” sound in “sells” and “seashells”;
• The “sh” sound in “she” and “seashore.”

These sibilant sounds give speech a hissing or sharp quality. Controlling sibilance is important in audio production to ensure clear and pleasing speech recordings.

Sibilant frequency is the range of frequencies in which the sibilant sounds are most pronounced. In audio and speech analysis, hissing frequencies typically lie at the high end of the audio spectrum, typically between 4 kHz and 10 kHz or higher. This frequency range is critical for sound engineers and producers as it must be identified and controlled in post-production, as excessive hissing can result in distorted audio or even discomfort for the listener.

Is it possible to use sibilance rather than just remove it?

This is where things get a little murky. The general consensus is that sibilance is, by definition, an unpleasant harshness in a recorded vocal. Fair enough. We spend a lot of time using plugins like de-essers to get rid of those overly powerful es.

The problem with calling all sibilance ugly and harsh is that there is a lot of pleasing clarity in that same frequency range. So it’s safe to say that to a certain extent we use sibilance to our advantage when mixing live, in-your-face vocals.

When working with this, the goal should first be to figure out how naturally bright your artist’s voice is. You can put a bright vocal on a dark mic, and vice versa, to tone down the harshness of the input. Then see how the vocal (hiss and all) sits in the mix as is. Does the whistle add a bit of presence and help cut through the vocals, or is it too harsh and distracting?

What are the different types of hissing sounds?

Hissing sounds are produced by creating a narrow opening in the vocal tract, which causes turbulence in the airflow. The different types of hissing sounds vary depending on the shape of the tongue, the place of articulation, and the point of contact with the tongue. Let’s look at the most common types of hissing sounds:

[s] Sound (Voiceless alveolar sibilant)

Tongue shape: the tongue is slightly raised, its front part touches the alveolar process – the bony protrusion behind the upper front teeth.

Place of articulation: alveolar, that is, the sound is formed when the air flow narrows on the alveolar ridge.

Contact point on the tongue: the air flow passes along the sides of the tongue.

Example: [s] as in the word “sea”

[z] Sound (voiceless alveolar sibilant)

Tongue shape: similar to [s], tongue raised and its blade touching the alveolar ridge.

Place of articulation: Alveolar, similar to [s].

Point of contact on the tongue: Difference from [s] is that the vocal cords vibrate, creating a voiced sound.

Example: [z] as in “zebra”

[ʃ] Sound (Voiceless postalveolar sibilant)

Tongue shape

Place of articulation: postalveolar, i.e. the sound is produced by narrowing the airstream slightly further back than the alveolar ridge.

Point of contact on the tongue: the airstream passes along the sides of the tongue.

Example: [ʃ] as in “sheep”

[ʒ] Sound (voiceless postalveolar sibilant)

Tongue shape: similar to [ʃ], the tongue is raised and its blade is located just behind the alveolar ridge.

Place of articulation: postalveolar, similar to [ʃ].

Point of contact on the tongue: The difference from [ʃ] is that the vocal cords vibrate, creating a voiced sound.

Example: [ʒ] as in the word “measure”.

How to Reduce “S” Sounds While Recording

Reducing the amount of “S” sounds in a recording is crucial to achieving a clean and pleasing sound. There are two main methods used to solve the hiss problem: “fix it at the source” or “fix it in the mix”.

• Fix it at the source: This method minimizes hiss during the recording process;
• Fix it in the mix: If there is still hiss in the recording, it can be removed in the post-production mix.

Combining these approaches allows you to effectively manage hiss and ensure a smoother, more professional-sounding recording.

Hiss can be a headache for those new to audio recording. It is often caused by poor microphone technique or poor microphone choice. In this digital age, producers love to tweak plugins. But with microphone recordings, you need to do it in real time.

Choose the wrong microphone or place it poorly, such as in a room with bad acoustics, and you will end up with a poor-quality recording full of hiss. What is the best way to eliminate this? Choose the right microphone and place it correctly. You will also need technical knowledge and a singer with the right technique.

Choosing the perfect microphone is not a walk in the park. You need one that not only reduces hiss, but is also suitable for your project. As a general rule, choose microphones that are less sensitive to high-frequency sound. Avoid those that emphasize the 2 kHz to 8 kHz range for hiss-free recordings.
Consider using directional microphones, such as dynamic microphones (such as the SM57). These help reduce the ambient hiss that sensitive condenser microphones can pick up. Of course, test different microphones to find the perfect one to minimize hiss and suit the needs of your singer.

A dynamic microphone may be suitable for heavy metal singers like Lemmy of Motorhead (who loved his SM57), but for intimate performances by artists like Billie Eilish, more sensitive microphones like condensers are needed. If you are working with a vocalist who needs a sensitive microphone, take steps to reduce hissing by proper placement and adjustment of the microphone. For example, with a sensitive condenser microphone, hissing can leak out if the singer is too close to it. So be sure to maintain an appropriate distance between them.

Experiment to find the optimal distance. If the singer is too close, you will get a hissing noise. If they are too far away, they will lose vocal power. Sometimes tilting the microphone away from the hissing noise helps, but it can reduce the quality of the recorded vocal performance. Consider using a pop filter to mute the hissing frequencies.

Pop filters can work well, but be aware that they can change the characteristics of the microphone. If you need a pop filter but don’t have one, use a sock over the microphone. Work closely with the singer to ensure proper microphone recording technique. Inexperienced singers may sing too close to the microphone or not through a pop filter.

Tips for Preventing Hissing While Recording

Start by positioning the microphone slightly away from the speaker’s mouth. This reduces the direct impact of hissing sounds and allows for a more even vocal tone.

It is also recommended to use a pop filter or foam windscreen in front of the microphone. This helps to disperse the force of plosive sounds (like “p” and “b”) and reduce the intensity of hissing sounds. Avoid speaking too close to the microphone, as this can amplify hissing sounds.

How to Reduce Whistling in a Mix

While it is best to prevent sibilance from occurring in the first place, there may be times when some sibilance slips through despite your best efforts. Below are a few techniques you can use to effectively remove sibilance in post-production.

Dynamic Range Compression

Compression is a common audio processing technique used to control the dynamic range of a recording. In the context of sibilance reduction, you can set up a compressor with a fast attack and release time to specifically target the sibilance peaks. By compressing the sibilance, the overall level of harsh frequencies is reduced, resulting in a smoother, more controlled vocal.

Multi-Band Compression

This is when you apply different compression settings to specific frequency ranges. In this case, you can set up a multi-band compressor to target the frequency range where the sibilance is most pronounced (usually around 4-10 kHz).

Manual Volume Automation

For more precise control, use manual volume automation to reduce the level of sibilance at specific points in the recording.

Equalization (EQ)

Equalization (EQ) is essential for reducing sibilance in audio recordings. By selectively adjusting certain frequency ranges, typically targeting the higher frequencies where sibilance is present (around 4 kHz – 10 kHz), an EQ smooths out sounds. With Auto-Tune Vocal EQ, you can make targeted cuts, monitor the results, and fine-tune for a polished, professional sound.

Using a De-Esser

A de-esser is a tool specifically designed to eliminate and control sibilance in vocal recordings. Its primary purpose is to reduce the harsh “s,” “sh,” “ch,” and “z” sounds that can be distracting and unpleasant to the listener. If you want to take your audio recordings to the next level and provide an immersive listening experience, consider adding a vocal de-esser to your toolbox. Its advanced algorithm automatically detects and targets sibilant frequencies, allowing you to effortlessly achieve a professional and balanced vocal mix.

So, you’ve recorded a band and got a great vocal performance, only to discover that the track has too much sibilance. Going back to the studio isn’t always an option. Maybe you no longer have studio time booked, the singer is unavailable, or the performance is too good to throw away.

You’re not alone in this problem. To fix sibilance, audio engineers have created a technique called de-essing. A de-esser is a specialized dynamic audio processor that reduces or eliminates sibilance. Nowadays, you can get a high-quality de-esser using audio plugins.

A de-esser isn’t groundbreaking. It’s like a compressor that selectively compresses sibilance frequencies when they exceed a certain threshold. You can adjust parameters such as the threshold and intensity of the compression and target specific frequencies. When used correctly, a de-esser can reduce harsh tones while maintaining the sound and quality of the original recording.

Studio Space Matters Too

The room you record in affects the hiss in your recording, so choose a room with proper acoustic treatment. Acoustically treated rooms absorb some of the hiss, resulting in less noise. Ensure effective and accurate monitoring of the microphone’s audio playback.

Amateur recordings often do not have sufficient monitoring settings, and hissing tones become apparent in other settings. If you are unsure of the quality of your monitoring, use headphones to check the hiss levels. Be sure to use studio-quality headphones, as commercial ones may color the sound in an undesirable way.

Using the Fader to Reduce Hiss

The primary role of the fader is to control the overall volume and balance of the mix, which indirectly affects how prominent the hissing sounds will be in the final audio recording. Here’s how to use the fader to eliminate hiss:

• Relative balance: Lowering the vocal fader can reduce the prominence of the hissing sounds, making them less prominent in the overall audio mix;
• Masking: Hissing sounds can sometimes mask other important elements in the mix. You can minimize the masking effect of hiss by allowing other parts of the mix to shine through.

A word about frequency masking, a common problem that engineers and producers regularly encounter. It occurs when one sound drowns out the clarity of another sound in the same frequency range, creating a muddy and unprofessional mix.

As for hiss, while you can use the fader to mitigate the problem, an equalizer is a better option. First, use a spectrum analyzer to identify conflicting frequencies. Although most sibilants are in the 3 kHz to 8 kHz range (female voices have higher sibilants than male voices), scan the entire spectrum to identify any potential frequency issues before applying an equalizer.

Next, use a combination of high-pass and low-pass filters to identify conflicting frequencies without compromising the clarity of the mix. By cutting and boosting frequencies, you can enhance dominant frequencies and tone down plosive sounds.

• Fader control: An engineer can manually adjust the vocal level in real time while mixing. When a sibilant word or phrase is encountered, they can quickly lower the fader level for those specific moments to reduce the intensity of the sibilance;
• Volume automation: In a DAW, faders can be automated to adjust volume levels at specific points in a recording. For example, you can automate a fader to reduce the volume during a vocal performance with a lot of sibilance.

Final thoughts

Hiss has a significant impact on a variety of audio production and communications environments, including radio, music production, television, podcasts, and more. Excessive hiss can be distracting, reduce engagement, and reduce the clarity of a vocal performance. With the skillful use of de-essers, equalizers, fader controls, and microphone recording techniques, you can effectively reduce hiss and improve sound quality.