Apple Final Cut Pro 6 - Manual (Page 917)

132 Part I Audio Mixing
5 Click the Level Keyframe button and reposition the playhead to place two keyframes at
the beginning of the click and two keyframes at the end of the click.
The two inner keyframes surround the problem samples, while the two outer
keyframes are placed a few hundredths of a frame outside of these.
6 Drag the part of the audio level overlay between the two inner keyframes down until
the box indicates –60 dB.
The unwanted noise should be gone, and the rest of your clip’s audio is not affected.
The problem samples
The overlay looks
something like this.