Removing Background Noise

We’ve all dealt with unwanted sounds when shooting on-location.  We’re recording dialog and an air conditioner kicks on or there is a noisy freezer running in the background that ruins an otherwise good take. Exterior sounds can cause the same problem.  In an ideal situation, we would turn off or unplug the offending sound and record another take.  Unfortunately, that is not always an option.

Record at least 30 seconds of room tone or location ambience whenever you’re on a shoot. Getting the sound of the space where you are will be valuable later.  Have everyone be quiet, leave the mic in the same position where you were set up for the dialog and then record. If you’re inside, record room tone with the air conditioner off and then on in the background.  And then there’s the noisy refrigerator or freezer too.  Get that background sound as well but leave the mic in the same location.

Capturing Noise Print
Captured noise print is now going to be removed

In post, you can import the room tone or outside ambience and, using your favorite audio editor, remove the background noise.  I like Pro Tools but I also use Adobe Audition.  Most audio programs have some type of noise reduction program where you can capture the noise print from a sound file and then remove it or greatly reduce it.  I’ve reduced the sound of the ocean during dialog on the beach and taken out microphone hiss when the signal was recorded too low.  The trick is to find a happy balance with how much background noise you take out.  Because the human voice often has some of the same frequencies of the sound your removing, it starts to make the dialog sound robotic if you take out too much. When it starts to sound unnatural, just back off on the reduction a little.

Unwanted noise being removed
Unwanted noise being removed

Even if you won’t be doing the post production audio work on a project, the editors and post sound team will appreciate the room tone and ambience tracks you record.  It’ll keep the dialog tracks clean and ultimately help make a better soundtrack.  If you found this article helpful, please share with your friends and colleagues.

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