Sound Capture - Plosives

Learning Outcomes

  • Define plosives and explain why they cause problems in vocal recordings.
  • Identify the speech sounds most likely to create plosive blasts.
  • Choose suitable microphone placement and accessories to reduce plosives at source.
  • Explain how microphone type, polar pattern and proximity effect affect plosive risk.
  • Apply suitable post-capture repair methods without damaging vocal tone.
  • Describe plosive prevention clearly in Component 1 recording logbook and exam-style answers.

Edexcel A-Level Music Technology (9MT0) Syllabus

In Component 1: Recording, you are assessed on your ability to capture, edit and mix audio effectively. Plosives are a sound capture issue, especially in vocal recording, because they can spoil an otherwise strong performance before mixing begins. You should be able to prevent them through planning, microphone technique and critical listening, and you should know how to describe your choices using correct technical language.

  • Capture vocals and spoken or sung parts with minimal unwanted noise.
  • Select appropriate microphones, stands and accessories for sound capture.
  • Position microphones to obtain a clean tone while reducing breath blasts.
  • Use critical listening during takes to identify technical faults early.
  • Apply suitable editing or processing only when prevention has not fully worked.
  • Explain recording decisions in a logbook using terms such as pop shield, polar pattern and high-pass filter.
  • Understand the difference between performance problems and recording technique problems.

Test Your Knowledge

Attempt these questions before reading this article. If you find some difficult or cannot remember the answers, look more closely at that area during your revision.

  1. What causes a plosive on a vocal recording, and which consonants are most likely to produce one?
  2. Why is a pop shield usually placed between the singer and the microphone rather than directly touching the microphone grille?
  3. How can angling a microphone slightly off-axis reduce plosives?
  4. Why might a cardioid condenser microphone close to a singer exaggerate low-frequency plosive thumps?
  5. Name two post-capture techniques that can reduce a recorded plosive, and one risk of using them too heavily.

Introduction

Plosives are one of the most common technical faults in vocal recording. They happen when a burst of air from the mouth hits the microphone and produces a low-frequency thump, pop or short blast. In a busy mix this can still be obvious, because the thump often appears below the main vocal tone and can trigger compressors, distort a preamp, or distract the listener from the words.

For Component 1 Recording, plosive control is mainly a sound capture skill. A well-planned session should deal with the problem before it reaches the DAW. Editing and EQ can help after the event, but the cleanest solution is to control the air movement before it strikes the microphone diaphragm. This means choosing suitable equipment, placing it carefully and listening back critically during the session.

Key Term: Plosive
A short burst of air produced by consonants such as “p”, “b”, “t”, “d”, “k” and “g”, which can create a low-frequency pop or thump when it hits a microphone.

How plosives are created in vocal recording

Plosives are part of normal speech and singing. To pronounce a “p” or “b”, the lips briefly stop the airflow and then release it suddenly. For “t” and “d”, the tongue releases air from behind the teeth. For “k” and “g”, the release happens further back in the mouth. These sounds are useful for diction, but they send a fast-moving air pulse forwards.

A microphone is designed to respond to sound pressure changes, not to be hit by a direct blast of air. When the air pulse reaches the microphone diaphragm, the diaphragm can move too far and too quickly. This movement is heard as a dull thud or pop, often stronger in the low-frequency range than in the main vocal sound. In severe cases the waveform may show a sudden large peak, and the sound may be distorted.

Key Term: Diaphragm
The thin moving part inside a microphone that responds to changes in air pressure and converts them into an electrical signal.

Plosives are not the same as sibilance. Sibilance is the harsh high-frequency sound produced by consonants such as “s”, “sh” and “ch”. Plosives are usually lower in pitch and feel like a pressure blast. In exam answers, confusing these two faults is a common way to lose accuracy. If the problem is a boom, pop or thump on “p” and “b” sounds, call it a plosive. If the problem is piercing brightness on “s” sounds, call it sibilance.

Plosives are often more noticeable when recording vocals close to the microphone. Close miking is useful because it captures a direct, intimate sound and reduces room sound, but it also increases the chance of breath noise and air blasts reaching the capsule. The Rhinegold study material stresses that close miking can reduce the amount of room sound captured, while greater microphone distance captures more of the surrounding acoustic. Plosive control is part of that same balance: very close placement may reduce room tone but create a higher risk of mouth noise, breath blasts and low-frequency problems.

Key Term: Close miking
Placing a microphone close to the sound source to capture a direct sound with less room ambience, but often with greater sensitivity to small noises and placement faults.

Test Tip: In Component 1 explanations, link plosives to sound capture rather than only to mixing. A strong answer might say: “I used a pop shield and positioned the cardioid condenser slightly off-axis to reduce plosive air blasts before recording.”

Preventing plosives before the take

The best way to manage plosives is to stop them being recorded in the first place. Once a plosive has caused distortion or clipped the input, it cannot always be repaired fully. Prevention is usually faster, cleaner and more professional than repair.

The most common solution is a pop shield, also called a pop filter. This is a thin mesh screen placed between the vocalist and the microphone. It slows and disperses the burst of air before it reaches the capsule, while allowing most of the vocal sound to pass through. Pop shields may be made from nylon mesh or perforated metal. Either type can work well if positioned correctly.

Key Term: Pop shield
A mesh screen placed between a vocalist and a microphone to reduce plosive air blasts before they reach the microphone diaphragm.

A pop shield should normally sit a few centimetres in front of the microphone, with the singer a little further back from the shield. If the singer’s lips are almost touching the shield, the air blast may still be strong when it passes through. If the shield is pressed directly against the microphone grille, there is little space for the air to disperse. A useful practical setup is to place the pop shield roughly 5–10 cm from the microphone and ask the singer to stay another 10–20 cm from the shield, then adjust by listening.

Distance is another key factor. Moving the singer slightly further away reduces the strength of the air blast reaching the microphone. However, this also changes the recorded tone. More distance may capture more room sound and may reduce the intimate vocal quality. For an A-Level recording, the aim is not simply “move the singer far away”; it is to find a sensible compromise between tone, room sound, spill and plosive control.

Angling the microphone can also help. Instead of pointing the capsule directly at the centre of the singer’s mouth, place it slightly above, below, or to one side, angled towards the mouth. The vocal sound still reaches the microphone, but the strongest air blast travels past the capsule rather than straight into it. This is called off-axis placement.

Key Term: Off-axis
A position away from the direct front-facing line of a microphone’s main pickup direction.

Singer technique matters too. A trained vocalist can reduce plosives by turning slightly away on strong “p” and “b” sounds, controlling breath pressure, or adjusting diction without losing clarity. In a coursework session, do not rely only on the performer to solve the issue. Use microphone technique first, then give simple performance guidance if needed. For example: “Keep your mouth aimed just over the top edge of the pop shield during loud lines.”

Another simple check is gain staging. Plosives can be worse if the microphone preamp is set too high. A sudden low-frequency blast may overload the input, creating clipping. Set levels using the loudest section of the song, including words with strong plosives, and leave headroom. A clean vocal take with a slightly lower recording level is far better than a loud take with clipped consonants.

Key Term: Clipping
Distortion caused when a signal level exceeds the maximum level that a system can record or process cleanly.

Exam Warning: Do not write that a pop shield “removes all popping automatically”. It reduces plosive air movement, but poor placement, excessive gain or very close singing can still cause problems.

Microphone choice, polar patterns and proximity effect

Microphone choice affects how likely plosives are to become a problem. Large-diaphragm condenser microphones are often used for lead vocals because they can capture detail, brightness and dynamic expression. However, they can also be sensitive to breath noise, mouth sounds and plosive bursts. This does not make them a bad choice; it means the placement must be controlled carefully.

Dynamic microphones are often less sensitive to small details and may tolerate loud sources well, but they can still suffer from plosives if used very close to the mouth. Handheld stage microphones often have built-in foam or grille protection, but a studio vocal take can still benefit from an external pop shield. Ribbon microphones can also be vulnerable to strong air movement, so direct plosive blasts should be avoided.

The microphone’s polar pattern also matters. A cardioid microphone picks up most strongly from the front and rejects more sound from the rear. Cardioid is very common for vocals because it helps reduce room sound and spill. However, directional microphones often show proximity effect when used close to the source. This means low frequencies are boosted as the singer gets nearer. Since plosives contain a lot of low-frequency energy, close cardioid placement can make them sound even more boomy.

Key Term: Polar pattern
The directional pickup pattern of a microphone, showing where it is most and least sensitive to sound.

Key Term: Proximity effect
The increase in bass response that occurs when a directional microphone is placed close to a sound source.

If a vocal sounds warm but suffers from heavy plosives, the problem may be a combination of close placement, directional pickup and strong consonants. Solutions include moving the singer back, using a pop shield, angling the microphone, or choosing a different polar pattern if the room allows it. For instance, an omnidirectional microphone has little or no proximity effect, but it captures more sound from the room. In a reflective classroom or untreated space, that may make the vocal less focused, so cardioid with careful pop control may still be the better choice.

Placement height is a useful practical tool. If the microphone is level with the mouth and directly in front, it receives the full blast of air. Raising the mic slightly above mouth height and angling it down can reduce plosives while keeping a clear vocal tone. Placing it slightly below and angling up can also work, though it may capture more chest resonance or breath depending on the singer. Always listen rather than relying on a fixed rule.

A foam windshield can help with light breath noise, but it is not always as effective as a separate pop shield for studio vocals. Foam covers are common for outdoor recording and live microphones, but in a close vocal recording a proper pop shield gives the air more space to slow down and spread out. Some engineers use both a foam windshield and a pop shield, but this can slightly dull the high frequencies, so use your ears.

Test Tip: When describing microphone placement, include the reason for the choice. “I placed the mic 15 cm away” is less convincing than “I placed the mic 15 cm behind a pop shield and slightly off-axis to reduce plosives while keeping a direct vocal tone.”

Identifying and fixing plosives after capture

Even with good preparation, some plosives may remain. The first step is to identify them accurately. Listen to the vocal in solo and in the full mix. A plosive may sound huge in solo but acceptable in context, or it may disappear in solo editing but still trigger a compressor when the mix plays. Look at the waveform as well: plosives often appear as short, large, uneven low-frequency peaks at the start of syllables.

A high-pass filter is a common repair tool. It reduces frequencies below a chosen cutoff point, allowing higher frequencies to pass. Since plosives often occupy the low end, filtering can reduce the thump. On vocals, a gentle high-pass filter may already be used to remove rumble. For a specific plosive, automation or clip-based processing can be more precise: apply stronger filtering only for the affected consonant rather than thinning the whole vocal track.

Key Term: High-pass filter
An EQ filter that reduces frequencies below a selected cutoff frequency while allowing higher frequencies to pass.

Clip gain editing can also work. If one “p” causes a large low-frequency burst, reduce the gain of that short section. This can stop it jumping out and can prevent compressors from reacting too strongly. The edit must be short and smooth, with fades if needed, so the word still sounds natural. If too much level is removed, the consonant may disappear and the lyric may become unclear.

Spectral editing, if available, can be used to reduce the low-frequency part of a plosive without affecting the rest of the vocal as much. This is a more advanced repair method and should be used carefully. In an exam or logbook answer, you do not need to claim advanced tools if you did not use them. Clear, honest explanation of simple techniques is usually better than vague claims about complex processing.

Compression can make plosives worse. A compressor responds to signal level, and a large low-frequency plosive can cause gain reduction that ducks the following syllable. If the compressor has a fast attack and the plosive is the loudest part of the word, the vocal may pump or lose clarity. For this reason, repair obvious plosives before compression where possible. You can also filter the vocal before it reaches the compressor, or use side-chain filtering on some compressors so low-frequency thumps do not control the gain reduction as strongly.

Editing is not a substitute for recording skill. If every line has severe plosives, retaking the vocal is often the best option. A retake with a pop shield and better positioning will usually sound more natural than dozens of repaired consonants. In Component 1, assessors are listening for the quality of capture as well as the final mix, so repeated obvious plosive repairs may reveal that the source recording was not well controlled.

Exam Warning: Avoid saying “I fixed plosives with reverb” or “I covered them with effects”. Reverb can spread the thump and make the problem more noticeable. Use prevention, editing, gain adjustment or filtering.

In your recording logbook, describe the practical decisions that improved the capture. For example: “During the first vocal take, strong ‘p’ sounds caused low-frequency pops. I moved the singer back from the microphone, added a pop shield, angled the cardioid condenser slightly off-axis, and checked the loudest chorus before recording the final takes.” This answer shows problem identification, corrective action and technical understanding.

Key Point Checklist

This article has covered the following key knowledge points:

  • Plosives are short air bursts from consonants such as “p”, “b”, “t”, “d”, “k” and “g”.
  • They often appear as low-frequency pops, thumps or blasts in vocal recordings.
  • Plosives occur when air movement hits the microphone diaphragm directly.
  • A pop shield slows and disperses air before it reaches the microphone.
  • Correct pop shield spacing matters; it should not usually touch the microphone grille.
  • Moving the singer back can reduce plosives but may increase room sound.
  • Off-axis microphone placement can reduce direct air blasts while keeping vocal clarity.
  • Cardioid microphones used close to a singer can exaggerate bass through proximity effect.
  • High-pass filtering, clip gain and careful editing can reduce recorded plosives.
  • Severe clipping caused by plosives may not be fully repairable.
  • Compression can make plosives more obvious if they are not controlled first.
  • In Component 1, describe both the problem and the practical recording solution.

Key Terms and Concepts

  • Plosive
  • Diaphragm
  • Close miking
  • Pop shield
  • Off-axis
  • Clipping
  • Polar pattern
  • Proximity effect
  • High-pass filter