Audacity comes with all kinds of effects that can help you polish your final product. Here we detail a few of the most useful.
Noise Reduction removes background noise and static from an audio file and is best applied after recording and editing are finished but before Normalizing the track as detailed below. If you plan to use noise reduction, record about five seconds of silence before you begin recording for the first time. If you forgot to record five seconds of silence, that’s okay. Just record five seconds of silence now.
When you have completed recording and editing use the selection tool to highlight your five seconds of silence. With these few seconds still selected, click the Effects drop-down menu at the top of the screen and then click “Noise Reduction.” When the window appears, click “Get Noise Profile.” This button will take a sample of the background noise from your five seconds of silence, and it will later filter that noise out of your audio file.
Once Audacity has the noise profile, select the whole audio track by clicking the open space under the “L-R” and Gain sliders on the left side of the screen, and then find “Noise Reduction” again in the Effects drop-down menu. When the window appears, select the “OK” button. This filters out the background noise in the whole audio track you selected.
Fading in and out
Audacity also has the ability to fade audio in or out. To do this, just select the track or section of audio you want to fade, then click “Fade In” or “Fade Out” from the Effects drop-down menu. These effects can be useful at the beginning and end of your recording, when transitioning from one segment to the next as well as when using music in a project.
Auto Ducking allows the user to play music that automatically fades into the background when someone speaks. When Audacity recognizes speech, the music will drop in volume but not fade entirely, and automatically raise back up when that there is no speech. Auto Ducking is, essentially, automatic Fading.
To Auto Duck music, your music needs to be the top track in the window. To do this, click its name above the gain slider and select “Move to Top” . In the Effects drop-down Menu, select Auto Duck. A box will appear with an graphic you can manipulate to adjust your Ducking settings. Here you can adjust how long you want the fade to be and at what volume the music should play in the background while someone is talking.
Experiment with different values. You can always undo your changes by clicking the Edit drop-down menu, then clicking “Undo.” The first and second vertices on the line graphic allow you to set amount of time that it will take the music to fade down when Audacity recognizes speech. The third vertex allows you to set how low the volume drops when the music Ducks. The fourth and fifth vertices allow you to set the amount of time that it will take the music to fade back up when Audacity does not recognize speech. Typically, the fade down and fade up times are identical, but this does not always have to be the case.
Normalizing sets the overall volume of an audio track to a constant level, removing major changes in volume that can occur during recording. To Normalize, select the track you want to Normalize. Once you have selected the audio, click the Effects drop-down menu and then click “Normalize”. When the text-box appears, look at the “Normalize maximum amplitude to…” option. This is where you will decide what the new maximum volume will be. Note that you can enter positive or negative values in this field. Once the new maximum volume has been set, click “OK”, and the audio levels will change.