Editing Audio Files

Chances are that you have a bunch of stuff at the beginning and end of the sound file that you don’t want: extra silence, the sounds of the mike being moved, etc.  There are several ways to get rid of stuff you don't want depending on how you want to handle the audio. Starting at the upper-left, you will notice that the Selection Tool Selection Tool is highlighted by default. This tool is often called an "I Beam" because it looks like a capital letter I. To begin, click the selection tool and click+drag over the area you want to edit.

  • If you simply want silence in place of the sound, select the area and click the silence button Siilent Selection. The selected area will be muted, and there will be a blank area the same length as the selected area.
  • If you want to get rid of everything but the selected area, click the trim outside selection Trim Outside Selection button and everything but the selected area will be muted. Note that the selected area stays at the same place in the track: if you play the sound back you may have quite a bit of silence around it.
  • If you want the area to go away and the two remaining bits joined with no pause in the middle, click the cut button Cut Button.

If you don't get the result you want simply click Ctrl + Z to undo the last task.

Moving a sound within a track: You might want to rearrange the sounds in a track: for example, in an interview you might decide that question 3 makes more sense after the interviewee has answered question 5. Simply select the sounds you want to move, click the cut button, then move the playhead to the point where you want to insert the sound and click the paste button Paste Button.

Moving a sound in time: You may well want a sound to start a little sooner or a little later than it does. To change when a sound starts, click the time shift tool Move Tool and click+drag on the track you want to move.

Adjusting the amplitude: Ideally, you’d like all of your sound files to play back at the same volume even if they were recorded at different levels. The fastest way to do this is by selecting the entire file by Edit->Select All and then adjusting the amplitude of the wave by Effect->Amplify. Make sure the box marked “Don’t allow clipping” is selected: if you’ve done this, amplify will adjust the loudest parts of the file to 100% volume and rescale the rest of it to match. (This process is known as normalizing.) Normalizing won’t really help if the sound file is all very soft (you’ll pick up too much noise) or if it’s too loud: it’s better to go back and rerecord.

Adding some silence: You may want to draw out the file in places. Audacity can generate passages of silence: simply move the playhead to the point where you want the silence with the selection tool and select Generate->Silence.

Adding irritating noise: If you really need it, you can also generate white noise or an irritating tone from the Generate menu. Try Generate->Tone and select 1000Hz square wave if you want flashbacks to tests of the Emergency Broadcasting System.

Mixing and matching:multi-track recording: Audacity's real power lies in the ability to mix multiple tracks. If you want to place a music track with your voice track, you can do so. As an example, select CD player from the record source pull-down and start a CD playing. Hit the record button and Audacity will automatically create a new (stereo) track for the sound. Hit stop after a little bit, then go back and play your new sound file. You'll hear both tracks at the same time, which will probably sound a little odd. However this option is great for personal use for Photo Story or Movie Maker that only your family or friends will see, when doing a presentation, movie or story for educational or promotional purposes, it is standard practice not to use CD's due to copyright issues.

You can also use multiple tracks to repeat sounds, say if you wanted the same snippet of music to appear several places. Select the sound you want to use again and go to Edit->Duplicate. A new track will be created with the selection: you are then free to move this where you need it.

Importing additional sounds: You don't need to record everything firsthand: you can import existing sound files directly into Audacity. Simply select Project->Import and browse to the sound file you want to import. Audacity understands WAV, AIFF, AU, IRCAM, MP3 and OGG files.

Splitting a MP3 into Two Separate Files:

  • Open the MP3 file.
  • Select the part of it that you want to be the first file by holding down your left mouse and dragging over the section. Listen to it by clicking the Play button.
  • While this part is selected, choose Export Selection as MP3... from the File menu.
  • Now select the part you want to be the other song and Export again.

Mixing Background with a Voice Over:

  • Open one sound (for example, the background music).
  • Select Import Audio... from the Project menu and open the other sound (for example, the voiceover).
  • Listen to your sound using the Play button. Audacity automatically mixes them together.
  • Choose the Time Shift Move Tool tool and adjust the position of one track or the other until they're synchronized the way you want them. You can even move tracks around while they're playing.
  • If you hear clipping which wasn't present in either of the original files, it means that the combined volume of the two tracks is too loud. Use the gain controls on the tracks to reduce the volumes until you don't hear clipping anymore.
  • Export as a WAV or MP3 file.

Adjusting the Loudness of Portions of Your Audio File:

The envelope tool, found on the Control toolbar, is useful for manually adjusting the loudness of any portion of your sample without actually affecting the sample itself. However, so long as you continue saving the file as an Audacity project, you will always be able to change the audio sample back to the original way it sounded. Envelopes are especially useful for editing interviews; if one person is consistently louder than the other, lower the louder person’s voice by creating envelope “handle” points around each loud portion, and lower the volume level.

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