Editing Audio Using Audacity

Editing Audio Using Audacity At this point, you should have audio files in the WAV or MP3 audio formats. If your audio files are not in one of those formats, please see the “Preparing Your Audio Files for Editing and Other Uses” handout for information on using iTunes to convert your audio to those formats. Audacity is a fairly easy-to-use program that allows you to import audio files, edit them, clean up audio and mix multiples files together. Once the files have been edited to your satisfaction, you can export them for use in Photoshop Elements, Premiere Elements or other multimedia software. A free copy of Audacity is available for download at http://audacity.sourceforge.net (download a regular version, not the Beta release). You must also download and install the LAME MP3 encoder from this web site; it increases the functionality of Audacity.

Setting up your Workspace When you open Audacity, go to Project Import Audio; in the file menu that pops up, navigate to the audio files you wish to import. Each file will open in a track in Audacity. We will refer to the window these files are open in as your “source” window. Once you have your files open, go to File New; the window that opens will be the workspace for the project you want to create. Then go to Project New Audio Track, and create a new audio track. You should perform this step once for each clip, or piece of audio that will be used in your finished project. For example, if you have eight audio clips you plan to use, you’d have eight new audio tracks. We will refer to this window as your “destination” window. You are now ready to begin editing.

Tools at your Disposal The Selection Tool Click this icon and your pointer can be used to highlight portions of the audio file. This allows you to edit and apply changes to individual portions of the file. The Zoom Tool Click this icon and your pointer can be used to zoom in or out on the audio track; left click to zoom in, right click to zoom out. This can be useful when editing the audio, since you can see more detail in the waveform and determine exactly which parts of the audio correspond with certain sounds. The Time Shift Tool Click this icon and you can move the audio in a track forward and backward along the timeline; this is used to determine when a clip should start or finish playing in relation to the audio in other tracks in the current project.

Basic Editing Operations Since you have multiple files open in the source window, you would hear all of the files at the same time if you were to press play. At the left-hand side of each file, there is a small set of controls, including a Mute button. Press the Mute button on every file except the one you want to take your first piece of audio from. You will now be able to hear that audio file alone. After playing your audio file to determine the start and end points, you can use the selection tool to highlight the section of the file you want to use. Highlighting works just like it does in Microsoft Word—click and drag to highlight the part you want, then use the copy button or the copy command to copy the selection. After copying a clip, go to the destination workspace and use the paste button to paste the selection into an open audio track. If you like, you can also use the keyboard shortcuts Ctrl+C and Ctrl+V to copy and paste instead of using the copy and paste buttons in Audacity. Once a clip has been pasted into an audio track, you can select the Time Shift Tool and move the clip forward or backward its track in the timeline until it is located where you want it relative to the other audio clips in your story. Once you’re done time-shifting your audio, select the Selection Tool so you’ll be ready to paste your next audio clip. Repeat the cycle of copying audio, pasting audio and using the Time Shift Tool several times, and your story will look something like this:

Effects In the Effects menu, you will find several options for improving your piece. If you need to change the volume of part of your track, highlight the area you want to adjust, then go to Effects Amplify. This brings up a menu with an adjustment slider. The slider defaults to the highest amplification possible, without clipping. Use the preview button to get a sample of what the selection now sounds like. If this is not enough, check the “Allow clipping” box and move the slider to the right or left to increase or decrease the volume. Clipping will decrease the quality of the audio. If you are trying to increase the volume, but the Amplify tool doesn’t increase it enough, you can increase the gain by using the gain control at the left end of the timeline for that track; the slider with the -/+ scale is the one to manipulate. But only do this as a last resort. When you increase the gain, the audio quality suffers. If you have natural sound or music in the background of your piece, you may want the volume of this background sound to gradually fade in at the start of your story, fade out at the end, or to gradually change volume before your narration begins or ends. To make such a gradual transition, highlight a few second of the audio at the transition point, then use the Fade In (gradually increase volume) or Fade Out (gradually decrease volume) function under the Effects menu. Play with these functions to get the effect you want; this is more an art than a science in Audacity. Sometimes, you may have unwanted noise in your audio track, such as a ceiling fan humming or a buzzing from your recorder. In certain circumstances, you can reduce or eliminate this noise with the noise removal tool. This is a two-step process. We’ll use the audio from your interview as an example. First, go back to your source window and find an area in the interview where neither you nor your subject is talking. Highlight this area. Then, go to Effect Noise Removal. A window will popup with two steps. You’ll want to push the button that initiates Step 1, Get Noise Profile. After pressing the button, the Noise Removal tool will close; this is normal. Next, go to your destination workspace and highlight the sound byte you wish to remove noise from. Then, go to Effect Noise Removal, which will reopen the Noise Removal Tool. You can now use the controls in Step 2 to adjust the amount of noise you remove. Use the preview button to review your work; you must make sure not to distort the audio you’re keeping. When satisfied, press the “Remove Noise” button. The shape of the waveform in the area you highlighted will change, indicating the removal has been completed.

Advanced Tools and Effects The Envelope Tool In your tool bar, you probably saw the button for the Envelope Tool. The Envelope Tool gives you the ability to fade in or out in the middle of a track or make gradual volume changes over a period of time. This is for more advanced or longer stories; for basic stories or users who are new to Audacity, you should stick with the simpler fade and volume controls mentioned earlier in this document. After selecting the Envelope Tool, when you move your cursor over the audio tracks, it will resemble the logo for the Envelope Tool. Once you’ve activated the tool, you’ll want to create what are known as control points. Control points mark the start or the end of a change in amplitude, and are what you manipulate in order to make that change in amplitude. To create a control point, click on the audio track you wish to edit, and a set of white dots will appear. This is your first control point. If you click somewhere else on the same audio track, your second set of control points will appear. Once you have your control points, you can create your fade effect. For example, let’s say you wanted your audio to increase in volume. Place your cursor over the first control point, hold down your left mouse button, and drag the control point up or down to the volume you want the start of your fade effect to be at. After releasing the control point, do the same thing with your second control point. Your audio track would now look like the example to the right. If you wish to change the location of a control point, place the cursor over that control point, hold down your left mouse button, and drag the point left or right to its new location. You can also use the Envelope Tool in place of the Amplify effect to change the volume of an entire audio track. If you create a single control point, you can manipulate that point until the volume of your track is at a level you’re satisfied with. High Pass and Low Pass Filters The High Pass and Low Pass Filters can be used in place of or in addition to the Noise Removal tool to remove interference or unwanted noise from your audio track. This works best if you know the approximate frequency of the noise you’re trying to remove; otherwise, it becomes a trial and error process rather than an exact science.

Be Careful When Highlighting Audio When you’re highlighting an audio track you plan to edit, make sure your cursor stays over the track you wish to edit. If you sweep over a neighboring audio track, you’ll also highlight that neighboring track.

The Pause Problem If you are listening to audio in Audacity and you press the “Pause” button, most of the tools and menus will be disabled. You cannot edit the audio while it is paused. You must press the stop button to regain functionality. That’s just the way it is.

The Project Sample Rate Problem You may experience a problem where some of your audio, when pasted into the destination window, changes speed. It may sound like the speed is doubled. If you look in the settings box to the left of that audio track, you’ll notice below the name of the track is a number followed by the letters “Hz.” That is the project sample rate in hertz. After pasting audio into your destination window, make sure the sample rate in that destination track matches the rate in the source track. To change the sample rate, click on the arrow next to the track name. This will open a drop-down menu. Go to the bottom of the menu, to “Set Rate.” In the menu that opens to the right, set the sample rate to match the rate in your source track.

Export When you have finished editing your audio, you must export your project as a WAV or MP3 file. Your Audacity project is not an audio file. Your professor or lab instructor cannot open the Audacity file for playback; other software programs cannot read the Audacity files for further use. The only way your project can be graded or imported into another piece of multimedia software is to export it as a WAV or MP3 file!! To export your project as a WAV, go to File Export as WAV. Save the file on the desktop of your computer; name it after yourself if you are turning it in after export, name it something logical if it is to be imported into another program with other files. To export as an MP3, go to File Export as MP3 and follow the rest of the export instructions in the previous paragraph. The exported file can now be turned in to your professor or lab instructor, or imported into other programs for further use.

10/08 Paolelli/Love