Transom Tools: Audacity

editing/mixing

Audacity

Editing wants to be FREE! An audio editing solution for Mac, Windows and Linux.

by Jeff Towne

There are lots of references on this site to ProTools and Adobe Audition and Nuendo and other sophisticated digital audio editing programs, but what do you do if you need to do some editing on a budget, or want to run lean-and-mean on a laptop, or are working in Linux? The audacious program Audacity might be worth a look. It has a few significant drawbacks, but has the benefits of being free, continually updated and improved, and will run on just about any operating system.

Here at Transom, we've dedicated significant space to tutorials about ProTools Free, because it is an amazingly capable free program and offered an easy entry point to the world of digital audio workstations if you had the right computer. But ProTools Free only runs on Mac OS9, and Windows 98 or Me (and not too reliably on either of those Windows platforms.) Now, in 2004, if you've bought a new computer it surely came with Mac OSX or Windows XP, neither of which can run ProTools Free. Or even if you're running an older computer, you may have banged-up against some limitations of the free program. So, we've recommended upgrading to the digidesign M-Box, an audio interface that's sold with a more capable version of ProTools. The $450 price is still quite a bargain for an audio interface with good mic pre-amps and an editing and mixing program with plug-ins, but even that expense is an impediment to some, and the fact that the M-Box must remain connected to use the program is a turn-off to many. And ProTools LE takes a pretty fast computer and lots of RAM to run well under OSX or Windows XP.

Audacity will run pretty efficiently under Windows 98, ME, 2000, & XP, Mac OS9 and X, Linux, and Unix. Go to their website at:

http://audacity.sourceforge.net/

Download the program, documentation and plug-ins. There are links to users groups, FAQs, tutorials, and one can submit requests for features and fixes.

There are a few shortcomings that make the program problematic for serious production, but used with some care, Audacity can be a convenient tool for simple editing or even multi track mixing. The biggest problem is the current lack of any kind of metering. There are no indicators of record levels, track levels or final mix levels. This is one of the most requested feature enhancements, so there's some hope that this will be added in a future release, but for now, it will take some extra vigilance to ensure proper level strength and to avoid distortion.

Work-around for the lack of metering:

One can eye-ball the waveform displays and get a sense of the level relative to full scale, and watch for the flattened-peaks that would indicate clipping. The best path is likely to be to experiment with your input levels and listen carefully.

If your audio interface and external devices allow inputting audio digitally, that path will avoid input gain problems. And one can improvise a meter for mix-down by importing a sound file with a –12dB 1khz sine wave tone into a stereo channel. Connect some device with reliable meters to the output of your computer's sound card or audio interface. A digital connection is best, but even an analog link to a DAT machine, even a cassette deck or reel-to-reel, will work. Play the tone, and if the connection is analog, adjust the input levels of your recorder to -12dB on a digital peak meter or 0vu on a VU style averaging meter. (more on levels here>>) That way, as you do your mix, you can keep an eye on the master level as you combine the tracks. And most importantly, listen, make sure there's no crunchy overdriving of channels that you might have noticed if you had a red flashing clip indicator on a meter.

If you don't have a sound file with a -12dB 1khz sine wave test tone, Audacity can make one for you, go to the "generate" menu and choose "tone." The generator has an odd control for level, not in dB but in increments between 0 and 1, but you can always make the tone, then go to the "effect" menu, "normalize" it, then reduce the gain by 12 dB with the "amplify" effect. Then export that as a .wav file and keep it to insert in future sessions as a reference.

Before you start a new project, go to your computer's sound control panel and make sure the desired input device, (whether it's you computer's built-in mic input, a sound card, or an external audio interface) is selected as the audio input source. Then boot Audacity and within preferences, set the preferred specs for your session. The audio I/O tab allows you to set up the device(s) you are recording from and playing to, and the default number of tracks that will be created when you click the record button. The Quality tab allows you to set the sample rate and bit depth of the project. Audacity can handle different sample rates and bit depths within a project, but these will be converted in real-time to the default session settings when needed. Although normally 16-bit is a sufficient bit-depth for radio productions, and you will save a good deal of disc space and processing power if you use that depth, Audacity sometimes creates grungy-sounding sound files when recording at 16 bit. I'd start with 16 bit, but if you have that problem, setting up your session to record at 32-bit float might solve it. The session can be dithered to 16 bit for burning to CD at the mix phase. Set that in the file format tab as the default export format. Make a new project, and check the lower left corner for the sample rate, you can change it there if you need to.

To record a new file, you don't even need to create a new track, just hit the red record circle in the transport panel, and a new track will be created. You can adjust the record level with the slider next to the little microphone icon in the top right corner, but ideally you should leave that slider fully up and adjust the level of your input device to prevent clipping at the inputs of your sound card or interface. If you have sound files already in your computer that you'd like to add to your session, select "import audio" from the project menu. You can import several types of audio files, including MP3s. They will automatically import to new tracks. You can name the track from the drop down menu next to the X in the top left of the track. Be careful, clicking the X deletes the track from the project.

Editing tools are similar to many other programs. The control toolbar is fairly standard with the expected tape machine-style transport buttons. Pressing the spacebar will start and stop play, and shift-spacebar (or typing L) will loop-play a selected region.

The selector tool allows you to click and drag over a range of audio in order to act on that section. Moving the cursor over the edges of the highlighted region allows grabbing and extending the length. Pressing Z moves the selection edges to zero-crossings, which reduces the likelihood of clicks at edits.

The envelope tool allows you to write volume envelopes, effectively automating a mix, much like the breakpoint volume automation in ProTools and other programs. Click on the envelope tool, then click on a point along the track to create a node, then click again to make another node and drag the node up or down to adjust the level. Dragging a node up and off the track will delete it. This technique can add a small amount of gain to the track as well as reducing it. Making only one node and dragging it up or down is a fast way to adjust the gain of the entire clip.

For overall gain changes to be applied to the entire track, use the "amplify" or "normalize" commands from the effect menu, or adjust the volume slider at the left of the track display. That slider sets the level for the track, but does not write automation for levels as the project plays, you need the envelope tool for that. Similarly, the pan control, located below the track volume slider on mono tracks, adjusts the track's overall left-right placement, but does not write automation.

The draw tool acts like the pencil tool in most audio programs, when zoomed down to the waveform level you can re-draw waveform data to eliminate clicks or other distortions.

The zoom tool is pretty obvious, click on it and then drag over a range of a track or tracks to zoom to that level. The magnifying-glass icons on the right hand side of the top of the track window can be used to zoom in or out in steps, to zoom to the selection, or to zoom out to see the entire project at once. If your mouse has a scroll wheel you can use that to zoom as well.

The Time Shift tool acts like the grabber in ProTools, use it to slide audio clips left and right in the timeline. Clips cannot be dragged from track to track, but a clip can be cut or copied and pasted into another track. If you wish to move an entire track, use the "move track up" or "move track down" command in the drop down menu at the left of each track.

The multi-tool mode will change functions depending on where on the track the cursor is located.

The Cut, Copy and Paste functions work as expected, and follow keyboard shortcut conventions as well. The trim to selection command is very handy, highlight the audio you want to save, click the icon with the wave inside the brackets and you'll delete everything except the selected region. The converse is accomplished by clicking the silence selection icon, it mutes the selected audio, but without moving any other audio regions, leaving a silent space, like hitting "mute" for that time range. All other edits will close up the gap, like working in "shuffle" or "ripple" mode in other editors. There is no "slip mode" so if you wish to eliminate sound without shuffling the adjacent audio together, use "silence selection."

The bad news is that the time shift tool works on all elements of a track, so there's no easy way to have a series of short clips in one track and slide them independently along the timeline. You can cut and paste, or "split" audio out to new tracks and slide those elements around, which solves the problem, but that can quickly add up to lots of tracks and make for an impractically busy track view if you have an involved or long project. You can make each track any height you'd like (grab the vertical edges of the track and drag) so once a clip is edited, the track can be reduced in size to get more tracks in view.

If you'd like to separate a region and move it to another track, use the "split" command under the edit menu. Select the audio you'd like to move, and select "split." Audacity will make a new track with the selected audio in it at its original time.

One way to work is to record or import your narration or actualities into the first track, then go through the track, and when you find audio that you might use, select it and use the "split" command which will drop that section out to a new track. Name that track so you can recall what that clip is. Repeat until you have all your potential clips in separate tracks. You can then go in and fine-tune your edits on each clip, and then drag them around in time to put them in order. You can then delete the original track by clicking the X in the upper left corner of the track, because it only has the audio you didn't use.

Editing is pretty straightforward: highlight audio you don't want with the selector tool and press delete. Audacity will shuffle the audio to close the gap. Use the silence selection tool (mute) if you'd like to remove audio without making changes to the timeline. You can always undo your edits, but they don't remain adjustable after you save, there are no edit marks that you can tweak later, you'd need to step backward undoing all your subsequent edits if you change your mind. So listen carefully and be sure you're happy with your cuts before you move on. Audacity saves relatively small ".aud" project files with all the editing data, so you can do multiple save-as steps to store different versions of the project, to retain flexibility without duplicating all the large sound files

Selecting view>>history will show you a list of your actions, and by clicking on the various entries, the edits will revert to that stage of the edit, you can then discard all moves after that point by clicking the discard button. The history list is cleared whenever you save, as in most programs, you cannot undo after a save. Audacity has been known to crash, so it's a tricky balance to decide when to save, when to save an alternate version, or whether to retain your undo buffer.

Edits are "destructive" in the sense that they are not always editable, but deletions and volume envelopes and effects to not overwrite the original sound files Audacity projects save quickly, as small ".aud" instruction files. When you want to save the audio as a new file, suitable for burning to CD or importing into another project, or FTPing to another location, you must export the project to a .wav or other such file. This will take some time, depending on the size of your project, and will write new audio data. You can export elements of a project by highlighting them and choosing export selected from the file menu.

Once you have your elements edited and on different tracks, you can slide them around with the time shift tool, and adjust their relative volumes with the volume slider at the left of the track window, or with the "amplify" command under the "effects" menu if one consistent level is sufficient. If you need to fade a track up and down, such as ducking music under a voice, use the envelope tool and click on the waveform to make nodes, then drag the nodes up and down to create a volume envelope. These volume adjustments remain adjustable, just grab a node and move it up or down, or drag it completely off the track to delete it altogether.

You can adjust tracks' left-to-right positions by using the pan slider at the left of the track window. Panning can not be automated at this time.

There are several helpful plug-ins, including a basic compressor, EQ, filters and normalizing. There are many others that should be used with caution, a few of them can give some pretty weird results. I've found the "Noise Removal" effect to be pretty ineffective, creating weird artifacts that overwhelmed any noise reduction. But even some of the crazier effects might be helpful in certain circumstances. The implementation of RTAS plug-ins in ProTools is a good deal more flexible, Audacity's effects need to be applied in non-real-time, one at a time, and once applied there's no going back short of stepping backward with "undo."

Once you have a mix of your elements (listen carefully and/or use the metering trick described in the sidebar to make sure your combined levels are healthy but not clipping) you can export your project (under the "file" menu) as a .wav file, or as an MP3, or as Ogg Vorbis, another kind of compressed file. Simply saving your project won't make a final mixed file, you need to export the project to get a coherent file you can burn to CD or FTP.

If you select all your tracks and choose "quick mix" from the Project menu (analogous to a "bounce" in ProTools, but faster) Audacity will combine all your tracks a single file, mono if you only have mono files, stereo if the project contains stereo files. Sadly the quick mix ignores panning of mono files and simply creates a mono file. Quick mix simplifies your project down to one or two tracks, but you still need to "export as" to use the mixed audio outside of Audacity.

As with any computer program, using keyboard shortcuts will speed up your work. There's a list of the default shortcuts here:

http://audacity.sourceforge.net/manual-1.2/keyboard_shortcuts.html

And you can even create your own custom shortcuts, as described here:

http://audacity.sourceforge.net/manual-1.2/keyboard_shortcuts_create.html

So, do you spend the money on a ProTools LE system or use Audacity and buy a nicer microphone? Producer Michael Fitzhugh had these perspectives:

If you're undertaking a modest endeavor, like editing together some anchors with a few stories for a half-hour show, this style of working is quite manageable. Just remember that, once you save or close your Audacity session, that "undo" history disappears and the current state of the session is "fixed". If you're working on an hour-long show including a lot of complex edits, you might consider the advantages of Pro Tools' non-destructive approach. Since it obsessively records every edit, you can undo individual changes in whichever order you please. This is a fantastic tool to have at your disposal, but comes at cost: namely, greater CPU and RAM usage.

When it's mixing time, Audacity provides a suite of useful tools. Basic fades can be managed by selecting the audio you wish to fade, then choosing the appropriate fade from the program's "Effects" menu. More exacting volume control is available by way of the "Envelope Tool", which allows you to place "breakpoints", which will help achieve the more subtle ducks and boosts Jeff Towne talks about in "The Mix" . While Audacity doesn't provide an automatic way to create cross-fades, like Pro Tools, these tools will likely support the majority of your fading needs. Audacity also provides the potentially useful option of "Label Tracks", which allow you to annotate your audio. The idea here is to allow calling out highlights. While this might be useful in some future version of the program, it has been unstable in all releases of the program to date and should probably be avoided for now.

~ Michael Fitzhugh
Michael Fitzhugh is senior producer of "On The Record", a feature program covering life in the San Francisco Bay Area for Berkeley's KALX.

The program has its quirks and impracticalities, but the price is right (free!), so it can be a good simple way to do some editing. Programs such as ProTools, Adobe Audition (formerly CoolEdit), Nuendo and others offer increased functionality and ease of use, but each of them are more expensive and more difficult to learn. If you are doing a complex production with lots of actualities and clips, Audacity might be impractical, but if you just need to do some simple editing, and mixing of a few tracks, it might be just the right program. And with its constant upgrade schedule, it may become significantly better as time goes by. And it's heartwarming to think that the developers might actually listen to you if you have suggestions.