Our industry is a psychotic technology marathon where video editors must be multidisciplinary and know how to do far beyond their primary occupation. Clients today often expect video editors to have basic sound editing skills in a world where everyone has a simple microphone in their pocket and hundreds of cheap recording devices available for purchase online; you will often need to use technology to reduce recording noise and enhance poorly recorded dialogue. Luckily, there are quite a few tools on the market that can help you improve the sound of the project you're working on.
How does It work?
In general, noise reduction tools work in such a way that they "learn" the noise: at this stage, you should select a piece of audio without dialogue, just background noise, so that the algorithm can sample it.
Then start playing with the parameters while listening carefully - the more noise you reduce, the more the dialogue will be affected accordingly. Be careful not to exaggerate! If you get to the point where the noise is completely removed, your dialogue will likely sound dull and strange.
Because the human ear is very sensitive to the human voice, noise reduction is about finding the delicate balance between removing the noise and maintaining a clear and natural dialogue.
Tip - always do A/B testing: once you finish cleaning the noise, switch between the original sound and the processed sound a few times to maintain perspective. I always prefer a bright-noisy dialogue to a muffled-quiet one.
Premier has a nice in-the-box set of tools for audio repairing.
Make sure your clip is selected, go to the ‘Audio’ tab, and choose ‘Dialogue’ under ‘Essential Sound’ (right side of your screen). You can find a deep explanation about this in the manual and also here. We will focus on the ‘Repair’ and ‘Clarity’ tabs:
Reduce noise - Obviously, this determines how much noise will be reduced. Keep the dialogue's clarity in mind!
Reduce Rumble - Can help you get rid of low-frequency rumbles (from a distant train or low wind noise, for example).
DeHum -Reduce noises from electrical interference of a single frequency in the 50-60Hz range.
DeEss - Very helpful! Cheap recording gear can sometimes produce a high frequency, very annoying noise called ‘Ess,’ which is an excessive prominence of sibilant consonants.
Reduce Reverb - Use it when dealing with dialogue recorded in a big hall or an empty room, where the echo is noticeable and exaggerated.
Dynamics - This is a compressor. It will enhance the overall level of the clip. You can use it if the volume level is too low. Keep in mind that a compressor function is to reduce the dynamic range, meaning that it will probably increase the noise level compared to the speech (That’s why you should record at a ‘healthy’ level - not too low, not too high).
EQ - To increase the dialogue's clearance, choose ‘Vocal Presence’ from the dropdown menu and start increasing it. Don’t over-process it, or it will sound small and thin.
Enhance Speech - You can choose the type of voice (Male or Female), and the algorithm will enhance the correct frequencies.
If you have Audition installed, you can use its advanced Noise Reduction tool to reduce background noises.
We mentioned the need to "sample" the noise so the algorithm will know what exactly to reduce:
Left-click on the audio clip and click ‘Edit clip in adobe Audition.’
Once Audition opens, select a part with no dialogue in it. Go to ‘Effects>Noise Reduction/Restoration>Capture Noise Print’ (Shortcut: Shift + P).
Now, click anywhere on the timeline, then go back up to ‘Effects>NoiseReduction/Restoration, and hit Noise Reduction(process)’ (Shortcut: Shift + Command/Control + P).
The Noise reduction effect will open up.
Start playing with the ‘Noise reduction’ and ‘Reduce by’ parameters and listen to the sound changes. Be careful not to over-process it! Once you think the sound is good enough, click ‘Apply’ and then press Command+S to bring the clip back to the Premiere timeline.
I won’t go into an in-depth and detailed explanation about this here, but you could achieve a better result by exploring two things:
1) The ‘Advanced’ tab (in the Noise Reduction effect window)
2) Clicking on the ‘Spectral Frequencies Display’ (Shift+D) will open a display where you can select different parts of the sound, repair and eliminate noisy elements if necessary.
You’ll first need to have Audacity installed on your computer. You can download it for free from here.
Once installed and opened, import your clip into Audacity. Then, find a part in the clip that doesn’t feature any dialogue and select it, where you can hear only the background noise. The algorithm will learn the noise pattern and then know what frequencies to decrease in your audio clip.
Go to Effect >> Noise Reduction...
Click on “Get Noise Profile”:
Click Command (Control for PC users) + 'A' to select the whole clip, and re-open ‘Noise Reduction.
First click ‘Preview’ with the given parameters. ‘Preview’ will play the audio file with the noise reduction effect but won’t apply it yet. Listen to it, and decide what to do next.
If there is still a significant amount of noise, start tweaking the parameters under Step 2.
My suggestion is to change ‘Noise reduction (dB)’ - this number signifies the amount of reduction that will take effect, and ‘Sensitivity’ - Controls how much of the audio will be considered noise.
Once you’re satisfied, click ‘OK,’ and the noise reduction effect will be applied to your audio file.
Finally, export the file to your computer (File>Export>Export as WAV/Mp3).
Mask the noisy audio with music
Try to do as much as you can with the noise reduction tools available to you, and then add a background track.
Use volume automation to make the dialogue stand out when needed, and most importantly - Use your ears!
You can even get more creative and try to use sound effects to mask specific noises. For example, if you have to deal with dialogue from a busy street, and suddenly someone is shouting in the background, you can add a honk sample to mask the shout.
Hire a sound editor
Sometimes you’ll find out that it is not that easy to remove noise without destroying the dialogue.
If you have the budget, it’s worth outsourcing the work to a professional sound editor who can make a chirurgical removal of all the little sounds that make the dialogue noisy and use the advanced tools that are available for sound editors, like Izotope RX, for example.
We sound editors also use EQ, Compression, and volume automation with advanced accuracy that allows us to be extremely precise when cleaning and editing dialogue.