GarageBand is an entry-level digital audio editing program from Apple that allows you to edit audio files. The "Edit" tab is an important feature of GarageBand as it allows you to add and remove several effects; you can remove distortion from GarageBand if it has already been entered in the "Edit" tab to the right of the GarageBand screen.
Open GarageBand and open your audio file. Wait for the audio file to finish loading and then click on the audio track from which you would like to remove distortion to select it.
Click the "i" symbol that is encapsulated in a blue circle on the lower-right portion of the screen. The icon sits in the center of two other icons, an eye and a set of notes.
Select the "Real Instrument" tab on the top right hand side of the screen. You will see two tabs, "Real Instrument" and "Master Tracks"
Activate the "Edit" tab by clicking it once. This will open up a list of effects. Look for the effect that says "Distortion." Click on the "Distortion" label and a drop-down menu will appear. Select "None" and the effect will be removed.
If you have distortion as the result of poor recording quality, in the "Real Instrument" "Edit" menu select "AULowpass in one of the boxes available. This will remove any frequencies above a certain range. This usually removes the distortion found in most recordings.