How to Sweeten Spoken-Word Audio and Dialogue in Resolve Using Fairlight

Having great audio for your video is pretty much essential to hold your audience's interest, but what does great audio mean? When it comes to dialogue, or really any audio for that matter, you are looking for the sounds recorded to be a listening pleasure.
Is it a pleasure to listen to the audio? In post-production we can apply some techniques to sweeten, or improve and clarify, the sounds you recorded. In this tutorial you'll learn how to use Resolve’s Fairlight tools to process a piece of dialogue that requires some touch up to the volume levels make it sound smooth and natural.

1. High and Low Filters
Let’s just get one bit of technical language out of the way: Compression. This can be a little tricky as it means different things depending on the context. Often it’s used to describe the act of taking a larger, high quality file and turning them into a slightly lower quality, with a much smaller file size. With audio engineering, compression means to reduce the dynamic range. In simple terms, it reduces the loudest parts of an audio signal while leaving the quietest part unchanged, evening out the highs and lows rather than trying to make all dialogue sound the same.
Before we start, we're assuming here that the audio you're working with is basically OK; you recorded clean audio at an appropriate level so that the audience can basically understand what you recorded.
Let's Get Started
The first thing we will want to do is even out the high and low end of the dialogue. To do this we’ll use the built-in Equalizer tool in Fairlight. Go ahead and open the Fairlight tab and Mixer pane at the top right of page. The EQ is located within the mixer. Double-click to open the Equalizer tab.

Figure 1

The Equalizer may look confusing, but we will go over it together. For this tutorial we won’t be using everything in this panel.

The blue line going down the centre represents how and when the EQ is modifying the input signal. By default it’s a straight line at 0dB, meaning not affecting the signal.

Band 1/High Pass Filter.  This allows higher frequencies to remain unchanged while filtering out unwanted lower frequencies.

Band 6/Low Pass Filter.  This removes high frequencies while a leaving low frequencies alone.

FIGURE 2

Add a High Pass Filter
Start by adjusting Band 1 or the High Pass Filter. Go ahead and click on Band 1 to engage the filter. You’ll want to adjust this to 100 Hz.

This is because unless your voice is in the range of a baritone singer, there isn’t much useful information below 100Hz. That range is mostly dealing with rumbles, hums, and plosives (the sounds created by 'P words'—try saying “Peter picked a peck of pickled peppers“ with your hand in front of your mouth and you’ll be able to feel the pops of air that are generated by those sounds). Secondly, lower-frequency sounds contain more energy than high-frequency sounds, which can lead to compressors being triggered unnecessarily. Both of the issues can be dealt with by filtering anything below 100 Hz. You can actually increase this level to around 120Hz depending on your sound system.
Play your audio back, and if you find your dialogue starts to sound unnatural in any way, lower the frequency until it doesn’t.
Add a Low Pass Filter
The next thing we will want to tackle is a Band 6 or the Low Pass Filter. Activate this the same way, by clicking on the header. Once again, this removes high frequencies and leaves low frequencies alone. Try adjusting this to around 13000 Hz. This is for the same reason, simply there isn’t much useful content in that range.
Go ahead and play back your dialogue. It shouldn’t sound too different from your original audio. Let’s close this window and move on to the next step. 

2. Add Compression
Navigate to the Compressor by clicking on Dynamics. There is a lot of information here, though for what we are doing, we only care about centre compressor column and the graph. Click on Compressor to activate it and you’ll see a yellow upward slopping line and blue vertical line appear on the graph. These lines represent the Ratio and Threshold.

Threshold: This controls at which volume the signal will begin being compressed. For example, if your have it set to the 0db, which is the max, your audio will never be compressed. On the other end of that if you set your threshold to the lowest, -50db, you’ll end up compressing everything but silence.

Ratio: When the input level goes past the threshold, the ratio determines how much our signal is reduced. For example, a ratio that is set to 2:1 tells any volume that exceeds the threshold to be divided by two. The higher the ratio value the more your volume at its loudest is reduced.

Attack: The attack is the amount of time it takes to turn on the compressor once the threshold is reached. 

Hold: The amount of time the compressor will stay on for after the threshold is no longer reached. This really depends on the situation and what kind of effect you’re after. I use this one loosely.

Release: This acts as a fade on your hold. 

Recommended Settings for Recordings of People Talking
The higher that you decide to set your ratio, the less natural your dialogue will sound. I recommend you start at a Ratio around 2:1.  For Threshold, you're generally looking for the loudest parts to be reduced by -3db.

FIGURE 3

You can monitor these levels with the Gain Reduction meter (the bar in the middle corresponds with compression). As soon as your input goes above your threshold, you'll see the meter activate. Try looping the loudest section of your track so you adjust the threshold until it’s averaging around 3dB.

3. Make Up Gain
Now that we’ve used compression to reduce the volume of the highest parts by -3db we can use gain to increase the overall volume, raising the Make Up by 3db. This way your loudest part is now back to the starting level and we’ve managed to bring up the quietest parts up in volume.
It's good to remember that there are multiple ways of adjusting audio levels and adding compression. There is no one approach that works for everyone. This, however, is a good starting place.

Keep Learning
That's it! Thanks for learning with us. Make sure to learn more about DaVinci Resolve's Fairlight panel by checking out these free tutorials.

Video
How to Sync Audio Tracks Automatically in Resolve Using Fairlight
André Bluteau
Video
How to Sync Audio and Video Tracks in DaVinci Resolve
André Bluteau