The Problem with Plosives

In this weeks posts I’m going to discuss a bane of many an audio guy’s existence, the dirty, evil wench we call ‘plosives’. 

The dictionary defines it as, “of or pertaining to a consonant characterized by momentary complete closure at some part of the vocal tract causing stoppage of the flow of air, followed by sudden release of the compressed air”. 

What the what?

Basically, in layman’s terms the loud, sudden burst of air produced when we say words containing consonants, like b, p, d, and t.  In everyday life, ‘plosives’ aren’t a nuisance at all, they’re actually an integral part of speech and communication, but when it comes to recording, they can be incredibly detrimental.  In recording they are more commonly referred to as vocal pops, because of the distorted “pop” sound they produce.  Most microphones can’t effectively handle this sudden burst of air, creating an asymmetrical distorted waveform on whatever recording medium you’re using.  For example, try holding the palm of your hand in front of your mouth while saying words that begin with b or p.  Do you feel that quick burst of air against your palm?  That is exactly what’s going into the diaphragm of the microphone.  The effect is basically mechanical clipping, and most every microphone is susceptible to this.

Waveform representation of a 'plosive'

Luckily for us there are ways around this devil.

Pop Filter

If you have one available, this will sufficiently diffuse the offensive burst of air, yet sometimes even a sweet pop filter won’t completely alleviate the nasty plosive.  When this happens your next line of defense is the microphone’s placement.  It’s advisable to rarely ever place the capsule of the microphone directly, and closely, in front of the vocalist’s mouth.   By moving the microphone to either side, or even slightly above with a combination of the pop filter, ‘plosives’ will be 99.9% eliminated.

Pencil Trick

Needless to say, I’ve had many a session where a pop filter wasn’t an option and microphone placement wasn’t doing the job.  A neat little trick I’ve picked up along the way involves taping a pencil (or pen) to the front of the microphone.  Believe it or not this actually kind of works when you’re in a pinch.  Try it out for yourself and see how it works.

Sometimes these nasty things rear their ugly heads after you’ve already tracked and mixing has begun.  In my next post I will give you a tried and true technique for eliminating ‘plosives’ from an audio track in ProTools.