[ To watch a video showing how this works in Audition CS6, click here. ]
There are some good noise reduction tools in Final Cut Pro X and Premiere Pro CC. However, it is often best to clean-up audio in a dedicated audio program, such as Adobe Audition.
This is Part 1 on Noise Reduction. Click here to read Part 2.
Noise is anything you don’t want to hear in your clip.
For example, in a football video, a cheering crowd adds energy to your video. But, in a sad death scene, a cheering crowd is distracting. Machine noises are interwoven with everyday life; unless “everyday” is the Middle Ages.
The easiest noises to get rid of are low-pitched hums. The hardest noises to get rid of are echoes and people talking in the background.
Why? Because all sounds exist as a series of rapidly changing frequencies. Human speech is roughly 200 cycles per second to about 6,000 cycles. (We use “Hz,” or “Hertz,” as the abbreviation for “cycles per second.”) Low frequency hum is around 60 Hz, so it is easy to separate voices from hum based on this frequency difference. Machine noise, like fans or air conditioners, are higher frequencies, but, generally, defined by some very specific pitches.
Not so the human voice. Pitch and volume range wildly. Worse, the frequencies of the talking you want to remove are, essentially, the same as the frequencies of the talking you want to keep. Removing voices behind your actors can be very, very difficult.
On the other hand, most of the time we don’t want to remove these sounds, we simply need to reduce them. After all, hearing the sound of the location is why we went to that location in the first place.
NOTE: I can’t stress this point enough. If you want to remove noise, your best – and sometimes only – option is to re-record your actors in an acoustically-treated room. This ALWAYS yields the best quality with the greatest control. However, syncing these new recordings with the originals is time-consuming and tricky.
OPTION 1 – Adaptive Noise Reduction
This first option is available in the Multitrack mix. The good news is that it is, essentially, automatic. The bad news is that it requires a short section of noise before your essential audio starts, then fades that noise out as the clip plays.
This is a clip from a trade show interview, with crowd noise throughout. (You can see the noise in the thickness of the “silent” portion of the clip before the interview starts.)
Effects can be applied to clips or tracks. I prefer moving all the clips that need the same type of repair into the same track so I can correct all of them in the same place and with similar settings.
After importing the clip, select the track where you want to apply an effect. Then, from the Effects Rack, click the small right-pointing arrow and choose Noise Reduction/Restoration > Adaptive Noise Reduction.
Audition warns you that this effect needs to be pre-rendered for best results. I’ll show you how in a minute.
A natural result of removing noise that the more noise you remove, the worse your actors will sound. The reason is that the frequencies that we don’t want are, in many cases, the same frequencies that we do want.
So, in this dialog, where you are able to select the amount of noise reduction you want, I tend to go either with the Default setting, or use Light Reduction. Neither makes noise go away – however, both will reduce the amount of noise so that you can hear your actors better.
Since I plan to render the effect prior to final output, I also check the High Quality Mode checkbox. After adjusting the settings, simply close the dialog box. There’s nothing to “Save.”
To pre-render the effect, look in the lower left corner of the Effects Rack and click the “Lightning Bolt” symbol. This turns on pre-rendering. There are no render settings you need to adjust. If you don’t see the symbol, make sure the track to which the effect is applied is selected. When you play the clips in this track, the noise will fade away after about two seconds until it is barely perceptible.
NOTE: When the symbol is blue, pre-rendering is on.
We can’t make bad audio sound perfect, but we can make it sound better.
Click here to read Part 2: The Noise Reduction Effect
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