Even highly prepared, attentive recording professionals occasionally find static or other unwanted sounds on their recordings. As a result, most digital audio recording and editing applications, including Apple's GarageBand, include tools for managing its impact on recordings. Two of GarageBand's built-in plugins -- the "AUGraphicEQ" and the "Gate" -- are particularly useful for reducing static in almost any recording. In some cases, it is even possible to eliminate it entirely. Results depend on several factors, including the overall quality of the recording.
Open GarageBand. Load the audio file you want to remove static from by clicking on "Open Existing File" in the project selection dialog. GarageBand will open the in its default arrangement area.
Press "Command-I" to open the track information pop-up. Click the "Edit" tab. The track's effects editor screen will appear. A "Noise Gate" will already be instantiated on the track. Click on the gray, rectangular button to the left of "Noise Gate" to turn on the gate effect.
Click on the first empty effect slot in the effects editor screen. A list of available plugins will appear. Choose "AUGraphicEQ." The AUGraphicEQ, with 31 bands, is the most comprehensive equalizer available to GarageBand.
Click on the AUGraphicEQ's icon in the effects editing screen. Its interface will appear.
Click "Play." The track will play back. As it plays, adjust the three or four farthest-right sliders on the AUGraphicEQ's interface. These sliders represent the highest audio frequencies in the recording. Most, if not all, static sound information will occur at these frequencies. Reducing these frequencies in volume will rarely affect the overall audio negatively, because very little desirable sound information occurs at this level. Experiment with different settings to see what works best for reducing the static noise.
Pull the noise gate's slider to the right until it reads -30dB. The purpose of a noise gate is to cut out all frequencies whose volume falls below the cut-off point. Setting the gate to -30dBs means that all sound information quieter than -30dBs will be cut out. This will completely remove all static sounds heard during lulls or silences in the recording.
Listen to the track all the way through with the noise gate at -30dB. In some cases, this setting may cut out sound information you want to keep in the recording. If this occurs, pull the gate's slider left in small increments until all desired sound information plays through.
Experiment with different equalization and noise gate settings. Together, these tools can reduce or remove static in most recordings. Static removal in GarageBand is not an exact science. Results will depend on the original quality of the recording, the settings used and many other factors beyond the control of most amateur audiophiles.
Open the "File" menu and choose "Save" when you are happy with the results.