The first fundamental tool for a podcaster is a good audio editor. Get started with Audacity, from importing a file into a project to making some simple edits.
I have a good friend who’s a carpenter and building contractor. A few years ago, in an effort to save costs, his small company and mine shared office space. One day, he was looking over my shoulder as I cleaned up a few lines of code for a client. “Man,” I heard him say under his breath, “that’s cool. I’d love to be able to do something like that.”
“But you do,” I told him as I turned. “You build stuff, I build stuff. We have different raw materials and tools, but what we do isn’t really so different.”
He looked surprised and more than a little self-satisfied as he answered, “Yeah, you know, you’re right.”
That’s really the point of this series of articles: to fill your toolbelt with all the open source tools you’ll need to build a quality podcast. You’ll need a hammer and nails, a saw, a speed square, a tape measure, a utility knife, and a pouch full of wood screws. You’ll need a little knowledge of the strengths of each and a bit of dexterity to manipulate them. You’ll need an understanding of the raw materials. And, you’ll need a process that works under a broad range of circumstances.
While your tool belt will contain quite a few tools, few are more important or utilitarian than the hammer. You can put things together and break things apart with a hammer. It can be a bit unwieldy, intended as it is for gross tasks rather than fine. But, it’s the tool you’ll reach for the most often in your podcast building project.
And, like hammers in the real world, audio editors in Linux come in a variety of sizes and weights. There’s Rezound, Ardour, Sweep, Muse, and a full range of other editors, each targeted to specific audio editing tasks.
For overall flexibility and ease of use, it’s tough to find a better open source audio editor than Audacity. I like to think of it as the 22-ounce framing hammer of open source audio tools. Audacity will do a lot of things and a lot of things well. But, its real mission is the brute force task of capturing and assembling all the discrete pieces of your podcast. In the case of a music podcast like The Roadhouse, that might be songs and musical segments, voiceovers and transition pieces (or “bumpers”) that give your podcast its distinctive flair. For voice-only podcasts like The ClarkCast, those pieces may include intros and outros, interviews, or long narratives that need “uhm”s and “ah”s removed for clarity. While the range of tasks will vary by podcast type and the style of the podcaster, the tools in Audacity will help meet your basic needs.
Let’s start with the most basic task of Audacity: capturing audio. Audacity will accept external audio from a variety of sources, including line in, mic inputs, CDs, and video sources. In general, though, these sources are determined by the capabilities of your sound card. For music podcasts recorded “on the fly,” it’s useful to have a stereo line in on the sound card. This line in will accept a full range of audio sources that you’ll pass through a mixer and out to the card.
If the podcast is an edited music podcast (not recorded live, but assembled from discrete pieces into a whole), a stereo line in on the sound card is less important. The same holds true with voice-only podcasts. Audio, including music, can be imported into Audacity in its full stereo glory, bypassing the inputs on the sound card altogether. For a good list of sound cards supported in Linux, see the ALSA Sound Card Matrix.
I’ll cover hardware, including sound cards, in much more detail in a later article in this series. For now, open your installation of Audacity. (Or download and install it from audacity.sourceforge.net. You’ll find source code and packages for Alt Linux, Debian, Gentoo, Mandriva, Fedora, SuSE, and Ubuntu.) We’ll start with the most useful components of Audacity – the pieces you’ll use most in creating your podcast.
Let’s start by importing a file into Audacity. Click Project → Import Audio from the menu and select an audio file from your system. This can be a wav file or an ogg file. It can also be an mp3 file, though you won’t be able to export it as an mp3 unless you’ve installed the lame libraries. Depending on the file size, it may take a few seconds or more to import. Once the file has been imported into Audacity, you’ll have a full view of its waveform in blue. If it’s a stereo file, you’ll see the channels stacked one on top of the other. If it’s a mono file, you’ll see only one channel.
In the full view, the peaks and valleys of the wave are almost indistiguishable – it appears as a single block of blue with some noticeable spikes. If the spikes reach beyond the top of the display, it’s likely that the file has some areas of clipping. This occurs when those peaks are cut off at the top by raising the input volume levels beyond the capability of the hardware or software. Those clipped peaks are abruptly flattened at the top rather than peaking and diminishing naturally. You may not notice the occasional single clipped wave during playback of the file. But, if the clipping occurs over long sections of the wave, the sound will be distorted and harsh. Bear this rule in mind when we begin to record. Let’s call it the first cardinal rule of sound recording: clipping is a bad thing. Once it’s occurred in a recording, it’s almost impossible to correct. It’s much easier to amplify a softer sound than to round and blend a flattened wave. It’s a good idea to record at conservative levels initially. You can always normalize and compress to bring softer passages up, and the sound will be much more pleasing. We will, of course, talk about normalization and compression in later installments of this series.
In the toolbar on the upper left corner of Audacity, you’ll find a play button. Make sure your headphones are plugged in, that the computer volume levels are reasonable, and press that button. The yellow hairline Audacity cursor will scroll through the wave from left to right as the sound file plays. This is a real-time visual representation of the sound captured by the file. Yes, you’re seeing sound without chemical enhancement.
Before the file is complete, press the pause button (two bars, side by side in the toolbar). Notice that the cursor stops and stays where you’ve paused the file. In the upper right corner of Audacity’s interface, you’ll find a set of magnifying glasses: one to increase the magnification, one to decrease. Click the increase button a few times and watch what happens to that solid blue wave. It begins to dissipate from the large blue mass into a series of peaks and valleys.
In fact, you begin to get a sense of the amplitude of the sound recorded in the file. While amplitude has several context-dependent meanings, (electrical engineers and radio engineers think of amplitude a bit differently) it’s always a measure of the height of a wave. The type of wave and measurement may differ, but in the end, amplitude always represents the displacement from a known zero plot to the peak of a wave.
In our context, it’s important to remember that sound has the distinct action of moving air. In fact, the peaks represented in your Audacity file— the high amplitude sections—represent power. More power pushes more air equals higher amplitude. And, because the air is pushed with more power, the sound is louder. The sound of a 747 taking off, heard from a distance of a hundred yards moves vastly more air than the sound of a pencil tapping on a desk from only a few feet away. That power is represented by the amplitude of the wave. The 747, even from a good distance, creates much higher amplitude sound waves than the pencil.
That’s an important fact to remember when working with Audacity. The wave representation in Audacity is not indicative of the frequency of the sound: it’s relative high or low pitch. It’s always a representation of power, of amplitude or, almost correctly, of volume. When a wave clips in Audacity, it’s because the source has overpowered the software or the hardware.
(Here’s another interesting if not terribly useful fact about Audacity. If you magnify the wave enough, you’ll begin to see what appear to be points on a graph. That is, in fact, exactly what they are. The line between these points represents a single sample of the source sound. In a file recorded at a 44.1 sampling rate, there will be 44,100 of these points per single recorded second.)
Now, back off the magnification a bit. You’ll see that the cursor has stayed centered in your view. Press the Stop button in the Audacity interface. The cursor returns to its original position, in this case, the beginning of the file. Click anywhere in the middle of the file, and the cursor moves to that location. Magnify again and notice that the cursor still remains centered in the Audacity window. Roll your arrow cursor close to the hairline cursor in the Audacity window. You’ll see a small left-pointing arrow appear as you approach. When you see that arrow, hold down the left mouse button and drag the mouse to the right. A highlighted area will follow your mouse cursor. This is the process for editing sections of your file. You can press the delete button to completely remove the highlighted area, or select Edit → Cut to remove the area from the display and place it on the clipboard for later pasting, using the Edit → Paste menu options. And, should you cut or delete a section erroneously, use Edit → Undo to reverse the action.
As you’ve seen, your editing in Audacity can be very, very granular: right down to the sample level. Select Edit → Undo to reverse your edit and magnify the file by a few steps. Highlight another area of the file and press the play button in the toolbar. Audacity will play only the highlighted area unless none of the file is highlighted, in which case it will play from the beginning. Listen closely to that highlighted section, then follow the same process to highlight a subsection to remove. This time, use Edit → Cut to remove the newly highlighted area. Highlight the area around your edit and listen again. You’ll hear the edit. We’ll talk in an upcoming article about blending and smoothing edits in Audacity, but you’ve now worked through the process of cutting audio.
Let’s add one more tool to the mix from the Audacity interface. Click Edit → Undo to replace the audio you cut. Then, select Project → Add Label At Selection. A new small track will open just below the wave window with a red flag at the current cursor position. To the right of the red flag, you’ll see a small rectangle. Click inside the rectangle and enter any text you think might be appropriate for the section. I use this feature often in The ClarkCast, noting the beginning and ending of a section to edit. You can place any number of labels on this track by following the above process.
Let’s look at two more more ways to use this audio hammer before wrapping this piece of the series. One is critical, the other very, very useful when editing a podcast with multiple tracks.
From the Audacity menu, select File → Save Project As. Select a location to which to save the project and click OK. Audacity saves each track and all its data as part of a project file. When saving projects, you’re actually saving a folder with the project data and an .aup file. The latter is merely an index of all the pieces of the project saved in the data folder. You’ll open this .aup file when reopening the project and, importantly, you’ll find your multiple tracks aligned exactly as you saved them. Some of the best experience I can pass along is to save your edits as projects early and often. It’ll save you from re-importing and realigning individual tracks.
Now for the critical piece. Let’s export the edited file. Click File → Export As [your preferred format]. If you choose to export as an MP3 file, you’ll need to have the lame libraries installed and configured within Audacity. Because the format is nearly lossless, I always export my final edits as WAV files. That assures that I’m working with the highest fidelity when I convert to MP3 using lame.
You should have an introductory feel for the framing hammer in your tool belt. You can already see the potential in this tool, having pounded a few nails. In the next installment of our series, I’ll show you around some of the finer points of Audacity. They’ll make the difference between whispering your message and shouting it.
