Editing : Edit Modes and Tools : Using the Pencil Tool : Waveform Repair with the Pencil Tool

Waveform Repair with the Pencil Tool
On audio tracks, the Pencil tool lets you destructively “redraw” waveform data. This tool is most commonly used to repair a pop or click in an audio file. A pop or click appears as a sudden sharp spike in a waveform. This tool only becomes active when the Edit window is zoomed in to the sample level.
Although you can Undo a Pencil tool edit, it is recommended that you create a backup copy of the target audio before using the Pencil tool. You can do this by using the AudioSuite Duplicate plug-in.
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The Pencil tool is a destructive editing tool that permanently modifies the audio file on disk and should be used with caution.
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For information about the AudioSuite Duplicate plug-in, see the Audio Plug-Ins Guide.
To destructively edit an audio waveform with the Pencil tool:
1 Locate the area you want to edit.
2 Using the Zoomer tool or the Zoom buttons, zoom down to the sample level so the waveform appears as a continuous thin line. Adjust the Track Height, as necessary, to edit the waveform with greater precision. You can also use vertical zoom for greater visual resolution.
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You can recall zoom levels with the Zoom Preset buttons (see Zooming Options), or with Memory Locations (see Recalling Memory Locations). The default setting for Zoom Preset 5 is at the sample level for Pencil editing.
3 Select the Pencil tool.
 
4 Carefully draw with the Pencil tool by dragging over the area of the waveform.
Do not over-edit or the results may be undesirable. However, you can use the Undo command to undo your previous edit.
 
The Pencil tool can independently edit different channels of a multichannel track.
Try to limit editing to smoothing over a very small problem area, and keep the “fixes” in character with the shape of the surrounding waveform.