If you need proof that editing is like turning a chunk of coal into a diamond, just listen to John Diliberto, the producer of Echoes. "That seven-minute feature that has three minutes of talking in it? That's edited down from an hour or so of interview material," he told me in "The Art of Podcasting."

Just as image editors like Photoshop gave us the power to zoom in on pictures and polish them to perfection, digital audio editors do the same for sound. In this article, I'll introduce some of the most useful audio editing commands and explain how you can use them to create your own sonic diamonds.

One of the most helpful skills you develop as you edit audio is the ability to "read" a waveform. With a bit of experience, you'll be able to look at a waveform and predict what kind of sound it represents and where the important changes happen. That mental map will enable you to quickly zoom in on the part of the recording you want to edit.

Figure 1, for example, shows the waveform for a famous three-word phrase, as displayed in BIAS Peak, one of the leading software audio editors. (See the sidebar for more.) The vertical axis, labeled 100 to 0 to –100, represents level, and the horizontal axis represents time. In other words, the height of the waveform at any given point corresponds to the volume of the sound at that instant. Notice how the first and third words ramp up to full volume gradually, whereas the middle word has a sudden, cliff-like beginning. It starts with a hard "G," whereas the other words start with a softer "Y" and "M." I like to imagine that the waveform diagram was produced by gluing a pencil across a speaker cone and rolling a long sheet of paper past it.

Vocal Waveform Figure 1. Can you guess what this famous one-second sound bite will sound like by looking at the waveform? Click here to find out.

P-Funk: Dealing with Plosives

In our article "Killer Interviewing Tips for Podcasters, Part 2," Jack Herrington covered vocal editing in detail. But one area he didn't have space to address is plosives, the bursts of air that vocalists generate when forming letters like P, B, and D. Plosives smack against a microphone, producing an annoying thump. With a pop screen and good vocal technique, you can minimize their occurrence, but they still creep in. Here are four ways Jack identified to remove them from a recording. Because the first two work similarly, I'll demonstrate the last three.

  1. Apply nondestructive volume envelopes.
  2. Select the pop and change the level destructively (using the editor's Change Gain function).
  3. Select the pop and use a low-cut (aka highpass) EQ to reduce the thump.
  4. Snip a few milliseconds out of the pop sound.

Figure 2 shows a P-pop in a vocal file I received recently.

Fig. 2: P-Pop

Figure 2. Notice the big spike where the audio level changes suddenly. It's an explosive P at the beginning of the word "piece."

Zooming in on the spike (see Figure 3), I deleted it.

Fig. 3: P-Pop

Figure 3. We have now zoomed in and selected about 26 milliseconds of the P sound so we can snip it out.

Figure 4 shows the same area, tamed with a level change instead of deletion.

Fig. 4: P-Pop -12dB

Figure 4. After processing with Peak's Change Gain command, the P-pop is now 12dB quieter.

Figure 5 shows the P after processing with a highpass EQ.

Fig. 5: P-Pop EQ

Figure 5. The height of the spike doesn't look much different after we filtered out the low frequencies, but it sounds quieter. Notice how it's denser horizontally. Low-frequency waveforms are wider.

The differences between these techniques can be subtle. For comparison, here is the sound again in its original state and then processed by EQ, gain change, and cropping, respectively.

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