What the POP?

How to fix the “POP” during recording or in post.

Before we can fix the POP, we need to understand where it came from.  To do that, let’s quickly look at microphone theory.  To oversimplify, sound waves hit a microphone and cause slight physical movement of the diaphragm, which is translated to electricity via an electromagnet.  If your mouth happens to be right in front of the microphone diaphragm and you have a loud plosive “P” or “T”, it moves the diaphragm substantially more than it should.  That comes through as a very aggressive (mostly low frequency) “POP”.

The best way to fix plosives is to avoid them in the recording.  A pop filter helps reduce plosives by allowing the audio to pass through while dispersing the air, reducing the amount of air that hits the diaphragm.  If you don’t have a pop filter, try moving the microphone position so that it is still pointing at the mouth, but the mouth is not necessarily pointing at the microphone.  Another trick is to put a finger between your mouth and the microphone to disperse the air before it hits the diaphragm.  This may not seem conducive to a natural performance, so I prefer one of the other techniques.

If you do need to fix it in post, just think about what you’re trying to get rid of.  First, the overall energy at that point is too high, so a gain reduction is necessary – through automation and/or dynamics processing.  Second, a High Pass Filter (HPF) will help roll off the very low frequencies, reducing the strength of the plosive.  Now combining those two concepts, we can use a multi-band compressor to drastically reduce the energy of the low band without affecting the rest of the frequency spectrum whenever the low frequency energy is too high.  I’ve actually listed these in the opposite order of how they should be processed.  Let’s check it out.

NOTE:  Since the writing of this article, iZotope has released RX5 Advanced, which has a one-click solution for removing plosives that is WAY better than all of these techniques combined!  This article is still valid, but if you really need to remove plosives in post, the BEST way is RX:

https://www.izotope.com/en/products/audio-repair/rx/whats-new/

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