What is a Pop Filter and Why Do I Need One?

A pop filter is a device used when recording that sits between the sound source and the microphone. It is most commonly used for vocals, but can also be used in other recording situations.

There are generally three types of pop filter:

1. Single nylon mesh
2. Dual nylon mesh
3. Metallic disc

Pop filters come with a clamp for mounting to a microphone stand and an adjustable neck for positioning.

Figure 1: Microphone And Pop Filter

Large professional recording studios tend to have at least two of each type - some engineers prefer one to the other. For a small home studio, however, most owners opt for a dual nylon mesh pop filter, as these are the most common and fit a tight budget.

Pop filters are used in the recording process to limit the effect of short bursts of high-pressure sound waves (generally referred to as pops). The pop shield reacts to the sound waves and reduces the high pressures heading towards the microphone.

Why are Pops so Evident?

Pops are heard mostly in vocals due to the ‘plosive’, consonant sound of words in song lyrics, such as the ‘B,’ ‘D', and ‘T’ in “Baby Did a Bad, Bad Thing.” Plosives are unavoidable - it's how we speak and sing. However, the effect of plosives can be minimized, as we will see later.

Pops are also heard on other instruments, for example, a close mic'd hi-hat will pick up the short bursts of high pressure when the top-hat closes down and pushes air out radially. This is more pronounced when the top-hat is more substantial, or the drummer is very energetic and slams the two hats together. I'd bet Steve Gadd doesn’t need a pop filter!

Air Produced by Vocalist - Plosives

Plosives are the consonant sounds ‘P,’ ’T,’ ‘K,’ ‘D,’ ‘B,’ and ‘G.’ We use them every day when we speak, and vocalists use them when they sing. A plosive sound is produced when air from the lungs is momentarily held by the throat and mouth before being released. The increased sound pressure is picked up by the microphone diaphragm.

Say the letter ‘T’ out loud a few times, and you'll soon understand the plosive mechanism. Say it loud enough at home, and somebody may even provide you with a freshly brewed cup of tea. ‘Tea!’, ‘Tea!’, ‘Tea!’.

A nice cuppa! Positive Effects of Practicing Plosives!

So, if plosives sounds are unavoidable, why don't I hear them on the music I listen to?

There are a few reasons why plosives sounds don't make it to the finished product:

• The vocalist has controlled their voice so that the plosive consonant sound pressure is reduced (not removed), to a level that is not noticeable.
• The engineer has set up the microphone off-axis so that the vocals are not sung directly into the recording. We'll discuss this in more detail later on.
• Each plosive occurrence has been digitally reduced by the mix engineer. There are automatic (plugins) and manual (clip gain reduction, selective EQ) techniques to achieve this. We’ll discuss these a little later on too.
• A pop filter has been placed between the sound source (vocalist) and the microphone (see discussion later on).
• Combinations of the above, or all of the above.

At your home studio, you may not have access to a professional recording engineer - you probably do that yourself. You also probably won’t have the most experienced vocalists or musicians either - there is nothing wrong with that, but we need to consider how to manage the recording and minimize unwanted artifacts, like pops.

And, the most practical way to avoid pops is with a pop filter. The advantages of a pop filter are:

1. Easy to use. All commercial pop filters come with a stand clamp and a flexible gooseneck. Positioning a pop filter is easy when you know where to place it and what its function is.
2. Plosives from vocalists are reduced before they reach a microphone’s diaphragm. With a little trial and error, you can soon figure out what works best for your microphone setup and vocalist. There are techniques for pop filter distances and angles that we'll see later.
3. A pop filter can also help to reduce sibilance (Hissing sounds of words like ‘SSS,’ ‘SHH,’ ‘ZZZ’).
4. The physical barrier of the nylon or metal reduces food or saliva being passed from the singer’s mouth to the internals of the microphone. Most microphones have a mesh guard, but these do little to stop debris from entering.

If you don't have the budget for a dedicated, high-end vocal mic and use something less suitable, a pop filter will help make the vocal recording sound more acceptable.

A pop filter can be used as a physical barrier to help inexperienced vocalists unintentional get too close to the microphone during their performance. Unless, of course, you have a vocalist, who thinks they know better where a pop filter should go!

It sounds like a pop filter is a great tool to use, but is there a downside? Yes, there is. The disadvantages of a pop filter are as follows:

• Using a pop filter can attenuate (reduce) high-frequency content of a recording. For example, the ‘air’ in a vocal or the ‘chick’ of a hi-hat. Sometimes these frequencies are filtered out anyway, but sometimes not.
• Anything that can reflect sound back to the microphone can cause unwanted standing wave or comb filtering. Using the dual mesh pop filter compounds these effects, as it is possible for waves to oscillate between the two nylon mesh surfaces, and oscillate between the pop filter and the microphone. See figure 2.

Figure 2: Pop Filter Reflections and Standing Waves

Apart from a pop filter, what else can be done to reduce or remove plosives?

1. Good Vocal Technique

In some cases, it'll be necessary to advise the vocalists exactly how far away from the microphone they need to sing. One reason for this is that inexperienced vocalists will stand way too close to a microphone. Another is they can not control their own vocal dynamics into the microphone well enough - the loud bits should be sung further away, and the quieter bits can be ‘in position’. Sometimes it is useful to take advantage of the low-end produced by the ‘proximity effect’ of the microphone, but not always.

2. Microphone Setup and Vocal Position

The microphone’s and vocalist’s positions can be set up so that the sound waves do not go directly to the microphone diaphragm. An alternative is to put the vocalist off-axis so that the sound waves glance the diaphragm. This is something that can be set up quickly, but make sure that you are not losing the vocalist’s uniqueness by moving off-axis.

Can I Make My Own Pop Filter?

Yes! Very easily. Take a steel wire coat hanger, open it out to a diamond shape, and wrap a single nylon pop sock over it. Then, duct tape it to a microphone stand. Ten-minute job!

But it looks awful! It's probably a little smelly, it’s difficult to mount and adjust, and to store away when not in use. So, the advice here is DON'T - don’t make your own. You can find budget pop filters online for as little as $8.99. Much better quality than a homemade one - looks good - smells new - easy to mount and adjust - and easy to store away.

If you are feeling extravagant, you can even upgrade to a $20 version! And if you do a lot of vocal recording and need to manage those plosives more seriously, go for something like the Stedman Proscreen – the daddy of all pop filters!

Joking aside, by all means, make a pop filter if it's an emergency and you want to record today. But when you do have time, get one for your studio. If you are recording vocals, it will get a lot of use.

Setting Up the Pop Filter

Now that you understand the function of the pop filter and realize its merits and limitations let's talk about setting one up. All pop filters come with a clamp, usually a G-clamp, which will open up to fit most microphone stand tubes. Set the clamp height to the point that allows the filter to be positioned about 6 inches in front of the microphone.

Basic Setups

Use the flexible gooseneck and swivel to place the pop filter parallel to the microphone body (See Figure 3). Place it 4 inches away from the microphone. Ask the vocalist to sing 2 inches in front of the pop filter.

You can put the pop filter closer - down to one inch or further away - up to six inches, but the 4”/2” rule works well in most situations, and it is a good starting point.

Figure 3: Microphone And Pop Filter Distances

There can be a minimal difference in performance between single and double mesh pop filters. A double mesh will increase the amount of standing wave because there are two nylon membranes. A single mesh pop filter counterintuitively filters more out - but I challenge anyone in a home studio to spot the difference between the two designs.

Advanced Setup

Again, use the flexible gooseneck and adjust the G-clamp position if necessary to angle the pop filter down towards the microphone (See Figure 4). Angle the pop filter about 30°. On a 6-inch diameter pop filter, that’s just over three inches back.

Figure 4: Pop Filter 30° Angle

By angling the pop filter down, the surface area restricting air pressure is increased, and therefore, the pop filter effect is also increased.

Additionally, the effects of standing waves and comb-filtering should be reduced, as air and sound waves are reflected away from the microphone diaphragm.

On a single mesh pop filter, waves traveling to the microphone are deflected up, and waves reflected from the microphone back are deflected down. Comb-filtering is improved, and the effect of standing waves is reduced.

It is possible to adjust the pop filter angle up to 45° or as low as 10°. But as with a lot of setups, if it looks right, it probably is, and 30° is a suitable starting angle.

Treating Plosives and Pops with EQ

There are more than a few ways to process your vocal tracks to reduce or remove the plosive ‘pops’. The process you employ will largely depend on your technical know-how and the extent of the ‘pops’.

Permanent High Pass Filter

Insert a High Pass Filter (HPF) into the first position on a track. Set the frequency to about 150Hz, listen to some offending pops and adjust the frequency if necessary. Leave the insert on the track, filtering out all of the audio. There is often very little audio information needed on vocals below 120Hz, so the HPF maybe enough on its own to remove the pops.

Selective HPF - On/Off

In this process, we are going to set up an automation lane to un-Bypass the ‘Permanent HPF’ (from the step above) only when it is needed. So, first insert the HPF and dial in the frequency. Next, set up an automation lane to control the BYPASS control of the HPF.

Figure 5: Selective HPF - On/Off Automation

Setting up an automation lane is different in each DAW. I use Pro Tools, but the method is the same in any other DAW, like Logic Pro or Presonas - check out some Youtube videos if you want to know how to set up automation in your own DAW.

Next, we're going to find every plosive that needs filtering and manually write automation to switch the HPF on and off.

Selective HPF - Sweep

Although the method above for switching the HPF On and Off is perfectly fine for most situations, here is a third method that gives a more specific level of control over the filtering.

Follow these steps:

1. Set up the high pass filter as described in ‘Permanent High Pass Filter’ (but set the frequency cutoff to 50 Hz).
2. Set up two automation lanes: One automation lane to control frequency and the other to control output. The output is the control on the DAW plugin to control the output level of the track. With these two automation controls, it is now possible to dial in the frequency amount for each plosive and reduce the volume of the pop.
3. Manually go through each pop and set the OUTPUT level and FREQUENCY. Note that you can sweep the two dials in and out. So, for example, the output can drop 0dB to -1.2dB and frequency can sweep from 50Hz to 170Hz and back to 50Hz.

Figure 6: Selective HPF - Sweep Automation

Although this method is a time-consuming process, you now have the technical know-how and the ability to dial out every pop individually without affecting the other parts of the track. You have also figured out how to set up an automation lane in your DAW, which is going to be very useful down the line!

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Final Notes on Pop Treatment

There are a few other methods for reducing pops in a track:

• Clip gain reduction - modify the track clip gain just for the plosives . This is a straightforward fix but does not always provide the level of control that is needed.
• Selective Compression. Use an automation track to bypass and un-Bypass a compressor to reduce the pops.
• With any Multi-Band Compressor, compress the low end and a little of the low-mid frequencies.
• Third-Party Plug-Ins - Try the Waves C1 Compressor on the de-pop preset or try Isotopes Audio RX.

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Metal Mesh Pop Filter

A metal mesh filter provides the same functionality as a nylon pop filter, but functions in a very different way. The metal screen has a series of punched dimples that are angled away from the microphone. As air meets the angled surface, it is deflected from its original path, and it is pushed into open space.

Because sound waves behave differently than air, they continue on their journey to the microphone. This phenomenon, known as diffraction, happens when sound waves meet obstacles they can get around, such as metal sheets or slits they can get through - such as the punched dimples.

The result is that air is deflected while the original sound waves arrive unharmed (almost!) at the microphone.

Managing Pops: Distance to the Microphone and the Proximity Effect

If you didn't know already, speaking directly into a microphone (about 0.5 inches to 1 inch away) makes vocals sound deeper and gives them increased low-end. Radio presenters and podcasters use this to their advantage to warm-up their voices.

The increased low-end is caused by low-frequency build-up in a microphone, causing some out of phase wave displacement. This is called the proximity effect - the closer you are to the microphone, the more significant the effect. Therefore, it is worth knowing if you are trying to manage plosives.

Due to the ‘pop’ from the vocal, the proximity effect amplifies the low frequency of the pop and makes them stick out on your track.

Keep the vocalist about 6 inches from the microphone. In some cases, the proximity effect will add about 16dB to the low end, but the amount depends on the type of microphone, the singer’s voice, and the distance between the sound source and the microphone diaphragm.

Related Questions

Does a pop filter reduce background noise? A pop filter does not reduce background noise. The pop filter is most useful for lowering plosive sounds produced by vocalists when recording. If you need to remove background noise, such as wind, what you need is a windscreen. A windscreen is a device most often molded from foam that fits snuggly over the head of the microphone. The windscreen also reduces vocal breath sounds and can be particularly useful for radio or podcast broadcasts. Another, although less effective, way to overcome background noise is to use a semi-circular reflection screen, which sets behind the microphone. These can help with reducing background noise in a home studio but are not practical for outdoor recording due to their size and weight.