Having the Audacity to Manipulate Sound
How to use the cross-platform program Audacity to edit sound files. [This article initially appeared in TUX, issue 6.]
by Joshua Backfield
Audacity is a cross-platform audio editor that provides some of the same abilities as store-bought audio editing programs such as Peak Express. This program has more capabilities than merely cutting and copying files; Audacity also can record from an input source, which goes along with mixing multiple audio files together. This is the same type of utility that Audio Production Studios use, although they use a hugely expensive program called Pro Tools.
I downloaded the source and compiled it myself, but most of you should be able to download the packages. You can use a package manager such as Kpackage or Synaptic to install Audacity, if it is available for your distribution. You also can install the packages with apt-get or yum at the command line. Finally, you can download Audacity as RPM or DEB packages and install them locally at the command line. For more information on downloading Audacity, visit audacity.sourceforge.net.
Getting Started with the Audio File
Let's assume you have installed the program and have it running. In this article, we are take an audio file and turn it into an audio preview file. We turn the stereo audio into mono, normalize the audio, crop it down to 30 seconds and use a fade in/fade out.
The first step is to open an audio file for editing. Go to the Project menu and select the Import Audio option. This brings up the Open File window. Here, select the audio file you want to import. Make sure the file that you are going to import is a WAV file before importing it. And, always make sure the audio file is stopped before trying to edit it. This means pressing the giant button with the Square in it to stop the file from playing. You also can press the spacebar to start/stop playing the audio.
Bouncing Two Stereo Tracks to One Mono Track
Now we have the audio file open that we are going to edit. Next, we need to split the left and right channels into their own separate tracks and then convert them into mono tracks. Figure 1 shows the menu to split the tracks into the left and right channels. Select the title of the audio track (on my track it is labeled “harder”). Once the menu comes up, select the Split Stereo Tracks option. You should now have two separate tracks; you will use this same menu shown in Figure 1 again to change the two tracks to mono. Select the title of each audio track, and select the Mono option.
Doing this allows the two tracks to be mixed together. Next, we mix the two tracks together into one single track, which is called bouncing. Select both tracks; you can do this one of two ways. You can select the audio pane, which is right under the drop-down menu you used to change the audio track to mono, and then select the other track while holding down the Shift key. Or, you can go to the Edit menu, followed by the Select submenu, and then select the All option. This selects all of the audio tracks in the entire project. Either way works the same for this project. You then need to go to the Project menu and select the Quick Mix option. This should bounce the two audio tracks into one single audio track. If done correctly, your audio file should now look something like the one shown in Figure 2.
Normalization Is Important in Audio
Normalization is the process of adjusting the loudness of an audio track so it is the same throughout the entire track. We select the new audio track by going to the Edit menu, then the Select submenu and then selecting the All option. Now go to the Effect menu and select the Normalize option. Keep the two options selected by default, and press the Ok button to begin the normalization process. After the normalization has finished, the audio file should have no large peaks or low valleys. This allows the audio track to have about the same loudness throughout. This also keeps the listener from constantly turning the volume up and down.
Creating the Clip with Fade In/Fade Out
Next, we cut out about a 30-second portion of the audio track. With the I cursor selected—this is the tool in the upper left-hand corner of the program that looks like an uppercase I--drag and select the portion of the song you want to keep.
You can see the length of the portion you are selecting in the bottom left-hand corner, as shown in Figure 3.
Select as much or as little as you want; in this example, I am selecting about 34 seconds of audio. Now that you have selected the audio that you want to keep, go to the Edit menu and select the Trim option. This also is known as Trim Outside Selection, which cuts off the audio not within your current selection.
Next, we place a fade in/fade out on the audio file. Take the I cursor and select only the beginning of the track, which will have the fade in. As shown in Figure 4, you can see that only the part of the clip that I want to have the fade in is selected. After selecting the portion of the clip where you want the fade in, go to the Effect menu and select the Fade In option to create the fade in for the track. Do the same for the fade out; except, instead of selecting a portion at the beginning of the clip, select a portion at the end of the clip. Then go to the Effect menu and select the Fade Out option.
Saving the File for All to See (and Hear)
We now have a 30-second mono clip, which has a nice fade in/fade out. Now, we need to get it out there for our friends to hear. To do this, go to the File menu and select the Save Project As option so that you can return to your project whenever you want. However, not everyone in the world can open an Audacity Project file (.aup file), so now go ahead and export the file. Because we have only a little bit to export, go to the Edit menu, then the Select submenu, and finally, select the All option to select all of the audio in the track. Then go back to the File menu, and select the Export Selection As WAV option, which saves your project as a .wav file that everyone should be able to listen to.
So Where Do I Go from Here?
You now can take your new WAV file and change it to an MP3, AVI, MPEG or AAC file using a program designed specifically for changing audio file formats. I have shown you the basics of the program Audacity; it is up to you to use it to its full potential. For most people, this program is considered “cool ”; however, for some new audio recording studios looking for a cheap alternative to Windows XP and Pro Tools, this program may be the perfect choice, especially because of its cross-platform abilities.
About the Author
Joshua Backfield is a 22-year-old student at Southern Illinois University Carbondale. He is currently doing his internship at Dupage County Convalescent Center, where he is helping people learn the benefits of using Linux.