Understanding the Causes of Mouth Sounds and Popping

Recording dialogue in close proximity—often within six to twelve inches of the talent—introduces a host of acoustic artifacts that go unnoticed at typical conversational distances. The primary culprits are mouth sounds (lip smacks, tongue clicks, saliva bubbles, breath noises) and popping caused by plosive consonants like p, b, t, d, k, and g. When a speaker articulates these sounds, a burst of air is expelled from the mouth. In close-miked situations, that blast can strike the diaphragm directly, producing a low-frequency “thump” or a distorted transient that is difficult to remove cleanly.

Mouth sounds arise from the natural moisture and movement of the lips, tongue, and palate. Dry mouth can increase stickiness, causing more clicks and smacks. Conversely, excessively moist mouths create soft, wet sounds. The close microphone captures these subtle noises with unnerving clarity, turning what is barely audible in natural conversation into an obvious distraction. The consistency of saliva plays a significant role: thicker, stringy saliva produces more audible separation noises when the tongue or lips part, while thinner saliva tends to create less friction.

Understanding the physics behind these problems is the first step toward solving them. Plosives behave as short, high-air-velocity events. The microphone’s proximity effect—a boost in low frequencies as the mic gets nearer—amplifies the low-end thump of a plosive, making it sound like a rumble or a kick drum hit. Mouth clicks, on the other hand, are high-frequency transients that cut through a mix and can be particularly jarring on sensitive condenser microphones. The transient nature of clicks means they often exceed the average program level by 10–20 decibels, making them stand out even in dense mixes.

Pre-Production Gear and Setup Strategies

The most effective approach to reducing mouth sounds and popping is to prevent them at the source. Investing in the right gear and configuring it correctly can eliminate the majority of issues before post-production. Every item in the signal chain—from microphone selection to the recording environment—contributes to the final sound quality.

Pop Filters and Windscreens

A pop filter is a simple mesh screen placed between the talent’s mouth and the microphone. It works by dispersing the force of the air blast from plosives, reducing the impact on the capsule. There are two main types: nylon mesh and metal mesh. Nylon filters are common and inexpensive but can slightly attenuate high frequencies. Metal mesh filters (often double-layer) allow better high-frequency clarity while still breaking up air bursts. For field recording or podcasting, a foam windscreen (sometimes called a “dead cat” or “blimp”) can also help, though it is less effective against plosives than a pop filter because it covers the capsule rather than creating an air gap.

For maximum protection, combine a large-diameter external pop filter with a foam windscreen. The gap between the pop filter and the mic gives the air puff room to dissipate before hitting the capsule. A distance of 2–4 inches between pop filter and mic is optimal; too close and the air burst may still reach the capsule. Some engineers also use a second pop filter in series for extreme plosive handling.

Microphone Selection and Polar Patterns

Not all microphones handle plosives and mouth noise equally. Dynamic microphones (e.g., Shure SM58, Electro-Voice RE20) are generally less sensitive to high-frequency transients and have better inherent resistance to plosives due to their heavier diaphragms and built-in windscreens. Many broadcast dynamic mics feature a “pop filter” grille design. Condenser microphones, while offering greater detail and a wider frequency response, tend to reproduce mouth noises more faithfully—including the ones you don’t want. If you must use a condenser for its clarity, pair it with a high-quality external pop filter and consider a cardioid or supercardioid pattern to reject off-axis noise, though be aware that hypercardioid patterns can have increased rear pickup of reflected sound that may amplify room artifacts.

Another factor is the microphone’s proximity effect. Cardioid mics boost low frequencies as the source gets closer. This can be flattering for voice (adding warmth) but exacerbates plosive thumps. Some microphones have a low-cut or bass roll-off switch that attenuates frequencies below 80–100 Hz, reducing the thump while preserving vocal intelligibility. If your mic lacks such a switch, consider using an inline low-cut filter or an EQ in the recording chain.

Proper Microphone Placement

Even the best pop filter cannot compensate for terrible placement. The standard technique is to position the mic slightly above or below the mouth axis, angled upward or downward by about 15 to 45 degrees. This “off-axis” position directs the blast of air away from the diaphragm. For dialogue, place the microphone slightly to one side of the mouth (e.g., near the cheek) and aimed toward the corner of the lips. This not only reduces plosives but also softens sibilance and mouth clicks.

Maintain a working distance of roughly 6 to 12 inches. Closer than 6 inches increases proximity effect and the likelihood of catching every small sound. Farther than 12 inches may introduce room reflections and reduce presence. The “fist test” works well: have the talent hold their fist between their mouth and the mic to gauge proper distance. For boom mics in film, the placement is often overhead and aimed at the mouth, requiring careful angling to avoid capturing nose breathing or heavy exhalations. In that scenario, the same off-axis principle applies—point the boom capsule slightly forward of the mouth to let plosives pass by.

Room Treatment and Acoustic Environment

A live, reverberant room forces you to move the microphone closer to isolate the voice, which in turn amplifies mouth noises. Treating the space with absorption panels, bass traps, and diffusion reduces background noise and early reflections, allowing you to use a slightly greater mic distance while still getting clean dialogue. Even simple measures like hanging moving blankets or using a portable isolation shield can help. A quieter room means less need for close-miking, which naturally reduces the prominence of mouth artifacts.

For podcasters or voice-over artists working at home, consider a reflection filter (a curved panel placed behind the mic) to deaden the immediate environment. However, do not rely solely on these; they do little to stop plosives and can cause comb filtering if placed incorrectly. Pay attention to the corners of the room—bass buildup there can mask plosive thumps during monitoring, leading you to underestimate the issue until post-production.

Monitoring and Real-Time Correction During Recording

Prevention extends beyond positioning. When monitoring the talent, use closed-back headphones to hear exactly what the mic captures—including subtle clicks you might miss through open-back headphones or room speakers. Apply a gentle high-pass filter (80–100 Hz) in the monitor chain to reduce the perception of low-frequency thumps, but remember this is only monitoring; you still need to record clean.

Some engineers use a compressor with a fast attack (1 ms or less) and a high ratio (4:1 or more) ahead of the recording device to catch plosive transients before they overload the converter. However, this approach can pump and color the voice. A better solution is to use a hardware de-esser or a dynamic equalizer that only attenuates bands where sibilance or clicks occur. Tools like the SPL Dynamax or a simple threshold-based limiter set to –3 dBFS can catch the occasional pop without affecting continuous speech. Always record at least 24-bit/48 kHz to retain headroom for post-processing.

Performer Technique and Preparation

The talent plays a critical role in clean audio. Encourage performers to hydrate well before recording—dry mouth produces more clicks and sticky sounds. However, avoid excessive drinking immediately before takes, as that can cause slurping noises. Some voice actors use a small sip of water or a slice of apple to moisten the mouth without creating salivation problems. Room-temperature water is preferable to ice water, which can constrict the throat and alter tone.

Coaching on plosive delivery can make a huge difference. Ask the actor to soften the “p” and “b” sounds by reducing the force of exhalation. Another trick is to turn the head slightly away from the mic when articulating plosive consonants. For persistent sibilance (excessive “s” and “sh” sounds), the performer can speak slightly off-mic or the engineer can place a pencil or finger vertically in front of the lips to break the air stream—a technique known as the “pencil trick.” This works because the narrow object creates turbulence that scatters the focused air jet responsible for sibilance.

Mouth noises often increase with nervousness or tension. Encouraging a relaxed jaw and controlled breathing reduces saliva build-up and tongue muscle tension. Short warm-up exercises that articulate plosives and sibilants can help the performer become aware of their mouth mechanics. For example, reading a rhyme-heavy passage containing many “p” and “b” sounds lets the actor practice soft delivery. Hydration timing is key: sip water 15–20 minutes before recording, then give the mouth time to produce normal saliva levels. Avoid dairy products and sugary snacks immediately before takes, as they can increase saliva thickness.

Post-Production: Editing and Processing

Despite all preventative measures, some mouth sounds and pops will always appear in a raw recording. Post-production offers several weapons to clean them up without ruining the natural quality of the dialogue. The goal is surgical removal while preserving the voice’s texture and dynamics.

Manual Editing

For short productions, manually locating and removing mouth clicks is viable. Use a spectral editor (like iZotope RX’s Spectral Layers or Adobe Audition’s spectral display) to visually identify clicks—they appear as thin, vertical streaks. Simply selecting and deleting or applying a gentle “spectral repair” can eliminate them. But for longer content, this becomes tedious. Many editors use keyboard shortcuts to quickly zoom and cut out audible breaths or smacks between phrases. When working on dialogue, listen in solo mode to spot these artifacts; a common workflow is to mark regions of silence and then inspect them for clicks.

De-essing and De-clicking Plugins

Dedicated post-production tools are designed specifically for these issues. De-essers (e.g., Waves DeEsser, FabFilter Pro-DS) reduce sibilants without dulling the rest of the voice. De-clickers (e.g., iZotope RX De-click, Accusonus VoiceGate) target transients like lip smacks and tongue clicks. They work by analyzing the audio and reducing the gain of short, spikey sounds. Most offer adjustable frequency ranges and sensitivity—set them conservatively to avoid artifacts. Overzealous de-clicking can create a phasey “watery” sound or remove necessary consonant attacks.

Also useful is a high-pass filter set around 60–80 Hz to eliminate low-frequency rumble and thumps from plosives that escape the pop filter. A gentle roll-off (12 dB/octave) is usually enough. For more aggressive cleaning, a multiband compressor can suppress the low-end burst of plosives while leaving the midrange intact. Set the lowest band’s threshold to catch peaks around 50–150 Hz without engaging on the voice’s fundamental.

Equalization

Mouth clicks occupy a wide frequency range, but many cluster around 2–5 kHz. Cutting a narrow (Q) notch around 3–4 kHz can reduce their presence, but be careful not to dull the voice. Alternatively, a dynamic EQ that only activates when a click triggers its threshold can surgically remove the noise without affecting continuous speech. Plugins like TDR Nova or FabFilter Pro-Q 3 allow you to set a sidechain trigger that listens for the transient and cuts just those brief events.

Plosive bursts are mostly below 150 Hz. A high-pass filter at 80–100 Hz removes most of the thump. However, if the voice has important low frequency content (e.g., a deep male narrator), use a steeper slope or a dynamic EQ that only cuts when a plosive triggers it. A low-shelf cut around 120 Hz can also help without fully rolling off the bass warmth.

Noise Gate and Expander

A noise gate can silence gaps between words, hiding tiny mouth noises that occur when the mouth moves before speaking. But a simple gate can cut off natural room tone or the tail end of words. An expander (a soft gate) gently reduces level during quiet sections, making it less noticeable while preserving a natural decay. A threshold set just above the level of mouth clicks (typically –40 to –50 dB) can effectively mask them. For dialogue, set the release time around 100–200 ms to avoid choppy transitions.

Advanced Techniques: Spectral Repair and AI Tools

Modern audio restoration software has made huge strides. iZotope RX offers a full suite: Mouth De-click, De-wind, Breath Control, and Spectral De-noise. RX’s Mouth De-click module uses machine learning to identify and remove clicks with adjustable artifact suppression. It can be applied in real-time or processed offline. Other tools like Waves Clarity Vx and Accusonus ERA bundle de-click/reverb/noise removal into one-step processes. AI-based tools are particularly effective at distinguishing between vocal transients and unwanted clicks, but they require careful parameter adjustment to avoid removing natural mouth sounds like the beginning of a consonant.

For film and television, dialogue editors often use AudioSuite or dedicated restoration suites to batch-process large amounts of production sound. The key is to use these tools in moderation—overprocessing creates a sterile, “robotic” sound that lacks vibrancy. Always A/B compare with the original to ensure you’re not losing natural texture. Spectral repair can fill in missing frequencies left by a removed click, but if you remove too much, the voice will sound hollow. Start with conservative settings and increase only where necessary.

Common Mistakes and How to Avoid Them

Even experienced engineers fall into common traps when dealing with mouth sounds. One frequent error is over-relying on post-production tools instead of fixing the source. A de-clicker can only do so much; if the recording has extreme plosives or constant wet mouth noises, the result will sound unnatural. Always prioritize placement, pop filtering, and performer coaching.

Another mistake is using a high-pass filter that’s too steep. A 24 dB/octave filter at 100 Hz can remove the body of a voice, making it sound thin. Use a 6 or 12 dB/octave slope and listen in context. Similarly, applying broadband de-essing on the whole track rather than only the problematic sibilant regions can dull the overall treble. Automate the de-esser threshold to increase only during prominent “s” and “sh” sounds.

Finally, failing to check the recording environment for low-frequency rumble (from HVAC, traffic, or electrical hum) can mask plosive thumps during recording, leading to surprises later. Use a spectrum analyzer to identify and treat these frequencies before you hit record.

Practical Workflow Summary

To combine all strategies into a repeatable workflow:

  1. Pre-record setup: Place a double-layer metal pop filter 2–4 inches from the mic. Use a long foam windscreen on the mic capsule for additional protection. Set mic at 45-degree angle off the talent’s mouth axis.
  2. Room prep: Minimize reflective surfaces with absorptive panels. Test walkie-talkie levels to avoid having to boost gain excessively, which amplifies noise. Check for low-frequency rumble with headphones and a spectrum analyzer.
  3. Talent coaching: Instruct to soften plosives, avoid exaggerated enunciation, and maintain consistent distance (fist test). Offer water (room temperature) and a small snack (apple slice) to moisten mouth. Do warm-up exercises with plosive-heavy phrases.
  4. Recording: Monitor with closed-back headphones and watch for plosives on the meters. If you see a thump, adjust placement or angle immediately. Apply a gentle high-pass filter in the monitor chain only.
  5. Post-production: Run a high-pass filter (80 Hz, 12 dB/octave), then use a de-clicker set to moderate sensitivity. Manually check problematic regions with spectral view. Add a gentle de-esser if sibilance remains. Use an expander (threshold around –45 dB, release 150 ms) to lower silence gaps. For stubborn clicks, apply spectral repair with a narrow selection.

Conclusion

Reducing mouth sounds and popping in close-miked dialogue is a multi-layered process that begins before the first take and continues into the final mix. By choosing the right microphone and accessories, positioning them intelligently, preparing the performer, treating the recording space, and applying precise post-processing, you can achieve dialogue that is clean, natural, and free of distracting artifacts. The investment in gear and technique pays off in listener immersion and professional credibility. Remember that no single solution works in isolation—combine prevention with correction for the best results.

For further reading, explore articles on pop filter design from Shure, microphone polar patterns from Audio-Technica, and advanced de-clicking workflows from iZotope. These resources offer deeper dives into the science and tools behind clean dialogue recording. Additional insights on vocal technique can be found at Voice Actor’s Guide to Plosives and on room acoustics from Recording Magazine.