Adding Labels to Identify Audio Segments
When working with any audio program, you should mark areas of your audio to help you identify different segments of your track. Editing audio visually using an ambiguous waveform can be difficult, especially with longer audio tracks.
Audacity, like many audio programs, includes a mechanism for labeling different areas of your audio track and using those markers to help you edit.
To label a particular area of your audio track, first click on the part of your track that you want to label with the selection tool, then select the Tracks menu and select Add Label At Selection, or CTRL-B (PC) Command-B (Mac).
A new special labels track will be created if you did not already have a labels track. Type in a name for the label you just created.
Labels should describe that portion of the track. Keep it short, so you can add multiple labels.
Adding multiple labels also helps you in the editing process by marking particular segments, and allowing you to select them.
Labels don't just have to mark a single spot, they can mark a span of audio with markers called boundaries. To expand a label to include a span of audio, roll the mouse over the label to highlight it first, then click and drag the boundary to the left.
Dragging to the left will open the label to include a span of audio, but dragging the boundary to the right will close the span or move the boundary to the right.
This span can be used to help you edit audio. Click on one of the boundaries with the selection tool, then drag the selection to the other boundary. You can do this in either the audio track, or the labels layer. If you highlight the audio track, then essentially you will be using the boundaries as guides to selecting your audio. If you highlight the portion that is in the labels layer (as seen below) you can use some special labels features to modify your audio.
Under the Edit menu, you will find the option for Labeled Regions. These pertain to regions of the labels layer that are highlighted. These options will only appear if you have a section of your labels layer highlighted.
There are lots of other features you can do with labels, such as exporting segments of your track to separate files using File --> Export Multiple. But those techniques are beyond the scope of this tutorial. Check out the Official Audacity Wiki for more information on labels.