Have you ever noticed that certain songs, headphones, or speakers produce a harsh, piercing high-frequency hiss, which makes you want to stop listening? That is called sibilance, which is caused by many different things.
First, you need to understand what the annoying hiss is, why it happens, and how to prevent it. And if it appears when listening to your headphones, you have to know how to eliminate, or at least reduce it.
What is Sibilance?
When talking about audio, the sibilance is the painfully hissing sound that is audible in specific recordings. It happens when a singer pronounces the word with consonants such as s, z, and t.
While we all produce a little bit of sibilance when speaking, some people’s sibilance is worse than others. It occurs because of the way we say those problematic letters. For example, when forming the “s”, we bring our tongue closer to the roof in our mouth, projecting the air into the upper teeth.
It’s the way our teeth grow (gaps between them), the shape of our tongue, and its proximity to the teeth, that generate the hissing sibilance. Some people might even be sibilant in real life when speaking to others.
Try to say: “Sally sells seashells by the seashore,” and evaluate how good you are at controlling the hiss.
The frequency in which vocal sibilance usually sits is around 5kHz to 8kHz, although piercing sounds can still occur at higher frequencies (cymbal crashes).
Sibilance in Headphones
Sibilance can be a tricky thing since it can already be present in the recording itself. Many factors result in a sibilant track, making your listening experience worse than expected: from the wrong microphone usage to incorrect microphone position and improper mixing.
However, some headphones can amplify the sibilant sounds, despite the same songs sounding fine on other audio equipment.
It has a lot to do with the tuning of the headphones. Bright, analytical, and V-shaped headphones are usually the ones that cause sibilance because they boost the upper midrange/lower treble frequencies.
While that brings out more detail, especially in the vocals, it can also exaggerate the hissing “s” noises. The result is a fatiguing sound that is impossible to listen to for extended periods.
How to Reduce Sibilance in Headphones?
You might want to consider these things before purchasing a new pair of headphones, especially if you’re sensitive to high frequencies:
Choose a headphone with rolled-off/smooth treble
To combat sibilance, many manufacturers tune their headphones in a way to subdue treble. Or at least reduce the specific frequency range that causes sibilance.
When a treble loudness starts continually reducing, we’re talking about “rolling-off”. That way, the high-end frequencies never reach a point of producing piercing sound. That takes a toll on detail rendition, but it’s much more pleasant to listen to for more extended periods.
Play with an EQ
If your existing headphones produce a lot of sibilant hissing, you might try out tweaking with EQ settings. You can either download the app for PC or mobile phone or use the EQ that is already built inside your existing app.
Try to find an equalizer with as many different frequency bands as possible. That way, you can choose and reduce the exact frequency range between 5-8kHz and see if it helps. There is a good chance someone uploaded the frequency graph of your headphones and left it on the internet. Try to find it to see where the peaks are, so you can later reduce them in the app’s EQ.
Sadly, this approach can affect the overall sound presentation, making your headphones sound a bit different than before. That is why it’s crucial to use EQ with lots of frequency bands, since you can fine tweak the sound, reducing the chance of completely changing the sound signature of your headphones.
Use different earpads/ear tips
The same way the speaker’s sound can be affected by room acoustics, different padding materials used on headphones, such as ear pads and ear tips, can change the overall signature. Every material acts as a sound absorbent, modifying a specific frequency range when those get in contact with it.
That is why leather earpads are known to boost the bass, making the sound fuller, while also slightly masking the treble. Velour pads are usually more breathable, offering a brighter and airier presentation.
The same thing applies to the silicone and foam tips on earbuds. Silicone tips provide a better seal, with fuller bass, whereas foam tips offer slightly more airy sound.
However, you should check the forums to see what other people are experiencing. Sometimes silicone ear tips produce more sibilance than foam ones. You should also note that changing earpads or tips might completely change your headphones’ sound. Hopefully, audio quality turns out better than before.
Use damping in front of the drivers
We are going into the modifying territory, where playing with your headphones can result in breaking them or voiding the warranty. So, you should take this step as the final resort to fixing the sibilance.
Like with the full-sized speakers, there are damping materials inside the headphone’s housing. With it, the manufacturer further shapes the sound that comes out of your headphones. Foam materials can be placed in front of the driver or behind it.
The least intrusive way of shaping the sound is by changing the foam inside the ear cup. That foam can easily be replaced and put back in. Again, try to find some advice on the forums, where people are already suggesting which materials are the best to achieve the desired effect.
Some modifications can also be done by opening your headphones, changing, or adding something internally. Doing so will expose the driver, making it vulnerable. If you haven’t done anything like that before, we advise you to skip this step.
Use passive headphone filters
This trick does not apply to all headphones, especially the wireless ones. That is because it involves placing a physical filter between the headphone’s cable and a source. Also, there is no universal filter since each of them is made for a specific headphone.
Filters use capacitors to tweak a audio signal that comes into the headphones, which evens out the output. The result is a reduction in problematic peaks, including sibilance.
However, getting one can be tricky since they’re not massively produced. If you know how to handle circuitry, you can do one yourself. Of course, you need the necessary parts and measurements from the internet to make a very specific filter. The other option is to contact someone who knows how to work around electronic circuits or order one online from a person who makes them.
Sibilance in Audio Recordings
The interesting thing is that even though some people are not sibilant when speaking in real life, their speech can be harsh when using the microphone. That is why vocal sibilance isn’t the singer’s problem in many situations, but the microphone’s.
Some audio equipment can’t handle the noise when we pronounce sibilant consonants, exceeding the dynamic range of what the microphone can pick up. That is why those sounds beyond the microphone’s range get clipped, leaving you with a fatiguing hiss.
How To Prevent Sibilance From Getting Into Your Recording
The best way to deal with sibilance is right before the recording starts. Eliminating it later can damage the overall quality of the final product, so it’s better to watch for these few things:
Pick the right microphone
Not all microphones pick our voices equally. Dynamic microphones, usually seen on stage, have a narrower dynamic range. For the studio work, condenser microphones are a much better solution.
Placing the microphone
When positioning the microphone in the studio, try not to place it right in front of your mouth. Consider putting it from 12 inches (30.5 cm) to 18 inches (45.7 cm) away from the singer. Sometimes it can also help to speak off-axis slightly, directing the sound of your voice away from your mic.
Angling the microphone on stage
Many singers like to hold their microphones in a way that looks cool. However, holding your dynamic microphone incorrectly may reduce the loudness of the picked-up voice and amplify the sibilance if the mic is too close to your mouth.
Use a chewing gum
You stick the gum to the roof of your mouth. This way, you can dampen the airflow that produces sibilance. However, this can also result in changing the overall singer’s pitch, so this method might not help everyone.
How to Eliminate Sibilance After Recording
If you did everything you can and still end up with some sibilance in the audio mix, it’s time to implement software-based solutions to combat the issue.
First, we need to understand how our ears work. During evolution, our ear canals formed in a way to amplify a human speech. That is why we need big subwoofers to play the bass, while tweeters usually are quite small and consume less energy.
That is important when mixing because some sounds in our waveform might appear loud, but we don’t perceive them as loud. Sibilance is at the frequency range where our ears boost the loudness, so in the waveform, sibilant noise can stay hidden. That is why correcting your vocal track afterward takes a little bit of time.
Use a fader
That is the most time-consuming thing since you have to reduce every sibilant frequency in the vocal track manually.
There are Frequency Selective (Split Band) and Wideband de-essing techniques. The first one involves reducing a specific frequency to eliminate the sibilance, while the other uses a broader range of frequencies. The result is a somewhat non-sibilant audio recording. However, it can also cause the vocals to sound dull.
If you’re more interested in the topic of eliminating vocal sibilance during or after recording, check this page for a more detailed explanation.