DaVinci Resolve Quick Tips: Fixing Audio Hum or Buzz with Fairlight
By Ross Papitto
We’ve all been there. You’ve spent days getting your lights and camera package ready for the big shoot. You got there early, set up your lights and camera and even splurged on that boom pole holder to save money on a boom-op. Your B-list talent strolled onto set only 20 minutes late, and after a quick tweak you were off to the races rolling picture and sound. Before you know it “That’s a wrap!” and you hurry home to your editing bay in the corner of your bedroom. You spend a few hours color grading finding the LUT that conveys JUST enough of the story’s angst without calling attention to itself, when suddenly, you notice something else calling attention to itself. You take off your Sony 7506 headphones thinking maybe it’s coming from the kitchen…maybe your roommate has fallen asleep playing Red Dead Redemption again. The noise disappears however when the cans come off, leading you to question the nature of your reality like a self-aware Host in a Westworld saloon.
“The hum is coming from inside the project.”
Turns out you spent so much time getting that Kino 4-bank in the perfect fill-spot that you forgot to kill the air conditioner in the room, leaving a low but irritating hum in your mic tracks; lav AND boom. Now normally you wouldn’t pay a seconds thought to the AUDIO of your piece. Afterall, waveforms aren’t nearly as sexy as 8k sensors and depths of field so shallow your 1st AC quit halfway through the shoot. However, this was supposed to be your big shiny new piece to pitch yourself to agencies, so you actually kinda want it to sound decent for a change.
You’re probably gonna want to De-Hum. Credit:MovieSetMemes
Thankfully DaVinci Resolve’s DAW Fairlight has a quick and easy fix so simple a grip can do it. It’s called De-Hummer. That’s right. You wanna de-hum your audio? Drag their De-Hummer plugin over to your audio channel. Still with me? You’re halfway there.
De-Humming is a drag and drop away…
The plugin has two default settings at 50hz and 60hz, because these are the fundamental frequencies of most alternating current of power mains. There’s also a “Variable” knob that lets you scan from 50hz all the way up to 400hz so you can really find where the hum is.
“Most of the hum energy is found at 60hz, with frequencies of lesser but still present hum heard moving up at the octaves 120, 180, 240, etc.”
By selecting “Listen to Hum only,” Fairlight allows you to isolate the fundamental frequency of the hum (OR WHERE IT’S LOUDEST, VIDEO GUY), as well as its decaying octaves moving up. If the hum is at 50hz, it will also be humming at multiples of 50hz; so 100, 150, 200, etc. Fairlights De-Hummer accounts for the drop in energy moving away from that fundamental as seen in the shrinking spikes of de-humming above.
The “Amount” dial lets you decide how much of those frequencies are being cut. Don’t go just turning it all the way up to 100 and call it a day. A lot human speech lives down there too, especially for men. Cut too much and you’ll start to hear the energy of the voice quiet as well.
The “Slope” knob switches the emphasis from the low octave of the hum to the high octave.Think of a Low slope as a more traditional hum and a High slope as a more high pitched buzz
A high Slope removes more of the buzz than hum.
That’s it! No really, that’s all it takes to eliminate annoying buzz in your audio tracks when editing in DaVinci. Drag the plugin onto the track with hum, switch to hum only to narrow in on it, and remove to taste. Just don’t forget to switch out of “Listen to Hum only” mode or your talent will sound like they’ve got a bag on over their head.