Audio Repair 101: Noise Reduction Basics

Get exclusive access to a comprehensive guide on noise reduction by Emmy®-winning dialogue editor John Purcell. Learn how to spot noises in recorded dialogue and other audio, and learn why you should fix some and let others go.

Audio Repair 101: Noise Reduction Basics

 

This is part 1 in a 3-part series:
  1. Noise Reduction Basics: Understand kinds of noises and how to control them
  2. Controlling transient noises: Clicks, crackles, pops
  3. Ambient Noise: Identifying and removing tonal and broadband noise
In Part 1, you’ll learn how to:
  1. Plan your workflow for repairing various noise issues in an organized way
  2. Recognize the different types of noises you will likely encounter
  3. Decide which noises should be removed and which should stay
  4. Maintain perspective to what should be done in the noise reduction stage, and what should be left for mixing

This is written from the perspective of film dialogue postproduction, but noise is noise, so what you learn can be applied to other audio recordings as well.

What to do about noise

The world’s a pretty noisy place. In the wild, in the city, and even in the library, it’s far noisier than you think: an onslaught of thuds, clicks, snaps; a never-ending stream of hums and buzzes; an irrepressible wash of whooshey, hissy noise. Oddly, these sounds usually go unnoticed in real life.

Shoot a scene on the beach, in a convenience store, near a generator, or even in a quiet office. On the set you may notice a few noises. They may be annoying, but usually not catastrophic. While you film the scene you understand every word of the dialogue, the interaction between the characters is believable and intimate, and the ambient sound goes largely unnoticed. Return to the cutting room and everything changes. The inoffensive background sounds overpower the words, there’s a strange hum you never noticed, and there are clicks of unknown origin. The characters are there, somewhere in the soup, but the track has lost its punch, drive, and accessibility.

When you speak with someone in a noisy environment, your brain filters out information that is irrelevant to the conversation. You can rely on body language and other visual clues, and perhaps a bit of voodoo and guesswork, to magically get you through the conversation.

A mic doesn’t benefit from any of this. It hears everything. Period. The noises you didn’t catch while you were filming have come back to haunt you. The tracks are a noise disaster and it’s up to you to resuscitate them. This is noise reduction.

Set proper expectations

There are very good processors out there that help you clean up messes in dialogue tracks. You can remove all sorts of noise, but you can, in the process, rob the characters of any hope of humanity and reduce room tone to a cellphone-like slosh. To avoid this almost inevitable sin of overprocessing, there are things to consider:

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