Apple Soundtrack Pro 3 - Manual (Page 237)

If a project includes an action that increases the file’s length, and you turn off or reorder
that action, any selection that includes audio added by the length–changing action may
extend past the end of the shortened file. In this case, the selection applies to the
remaining audio in the selected range of time, but has no effect past the end of the file.
For example, if you have a five-second project that includes a one-second Insert Silence
action at the beginning of the project, and you select the last half-second of the project,
then turn off the Insert Silence action, the selection applies to the last half-second of the
project. However, the remaining half-second of the selection is empty.
Overview of Analyzing and Fixing Problems in an Audio File
Soundtrack Pro includes a set of audio analysis tools. You can analyze an audio file for
common problems and fix them individually or in a single operation.
There are different types of analysis you can perform:
• Clicks and Pops: Sudden, short peaks in the audio file can result from a variety of causes,
including mechanical defects in analog recordings. You can set the threshold above
which Soundtrack Pro considers peaks to be clicks or pops.
• (Power Line) Hum: Power lines and other electrical equipment can produce a steady
hum, often at 50 or 60 Hz. The hum can also include low-order harmonics of the
fundamental frequency.
• DC Offset: DC offset is a shift in the audio, causing the positive and negative parts of
the signal not to average to zero. DC offset can limit the dynamic range of an audio
file.
• Phase Issues: Phase issues can result from a distorted or inaccurate stereo image, caused
by poor microphone placement or other issues. When converting a stereo file to mono,
the presence of phase issues can cause the left and right channels to cancel each other
out partially or completely.
• Clipped Signal: A clipped or overloaded signal can result from several causes, including
poor gain staging in a preamp during recording, bad electrical cables, or surface damage
to an analog recording. If analysis identifies a clipped signal, Soundtrack Pro gives you
the option to soften the abrasive nature of the truncation.
• Silence: Silence detects the parts of the audio file at which the audio signal falls to zero
(0). You can set the threshold below which Soundtrack Pro considers the signal to be
silence.
The Power Line Hum, DC Offset, and Phase analysis types determine whether the audio
file or selection exhibits these problems. Because hum, DC offset, and phase issues tend
to last for long times, up to the entire length of the file, better results might be achieved
when analyzing the entire audio file or the part of the file you think has the problem.
237 Chapter 8 Working in the File Editor