Dialogue Editing

Reducing Ambient Noises 223
processors to remove harmonic noises or unwanted transients, you end up
asking too much of the broadband processor, which repays you with a signature
“I’ve been noise reduced” sound. The trick is to identify your particular
noise problem and then apply the correct processors in the right sequence
and in the proper amount.
Remember, you’re not mixing the dialogue at this point—save that for later.
Right now you’re just doing cleanups that would be too time-consuming or
expensive in the dialogue premix. Don’t bother with the shelving and
“shaping” that naturally apply to all of the dialogue elements. Almost all of
your tracks will have some low-frequency rumble, which the mixer will roll
off in the premix. Don’t attack these problems in your cutting room; address
only the odd but exceptional noise problem there.
A Typical Noise Reduction Plan
The following paragraphs describe a typical multipass noise reduction
sequence. Usually, you will work in this order:
1. Use fi lters to remove rumble, buzz, and hum.
2. Use interpolation processors to remove crackle that occurs when
words are being spoken.
3. Use broadband processors to remove random noise.
4. Use fi lters again to remove remaining harmonic problems.
Rumble, Hum, and Buzz Removal Create an FFT or spectrogram of your
noise, 6 and look at the low-frequency information (below 500 Hz), as shown
in Figure 12-10. If you’re chasing a harmonic problem like a rumble, hum, or
buzz, you’ll notice a distinct pattern. Look for the lowest-frequency peak in
the FFT—that’s the fundamental frequency of the noise. You should easily
see harmonics occurring at multiples of the fundamental frequency. You can
also analyze harmonic patterns using a spectrogram, as shown in Figure
12-11.
Write down the center frequencies of the fundamental and its harmonics, up
to the tenth harmonic (or until you can’t stand it any longer). Note the
6 An FFT, or Fast Fourier Transform, equation is a method of studying a signal in the
frequency domain rather than in the time domain (in which we live). Sonic Studio and a
few other DAWs provide an FFT display for analyzing a signal. Pro Tools has no onboard
means of doing this, but a number of plug-ins allow you to create a display showing the
signal FFT. A spectrogram is another means of displaying frequency domain sound
information.