Apple Logic Pro X - Manual (Page 322)

Chapter 10 Create a song arrangement 322
Remove silent passages from audio files
Remove silent passages in the Strip Silence Window
You can remove silent passages from audio regions in the Strip Silence window. The basic
process is simple: all amplitude values below a threshold level are removed, and new regions are
created from the remaining passages.
The parameters of the Strip Silence window are:
•
Threshold: Use to define the amplitude level that a passage must exceed, in order to be
defined as a region. In terms of the number and length of regions created by the process,
this is the most important parameter. As a general rule: a higher Threshold value leads to
numerous short regions. Low values create fewer large regions.
•
Minimum Time to accept as Silence: Use to define the length of time that a section must be
below the Threshold value, before it is considered a gap. Very small values tend to increase the
number of regions, because even short dips in amplitude are interpreted as silence. Higher
values prevent sections of audio from being interrupted by fluctuating amplitudes.
•
Pre Attack-Time: Use to add a defined amount of pre-roll to the beginning of all regions
created by the Strip Silence process. High threshold values prevent any amplitudes with slower
attack times from being chopped. This function is useful for nonpercussive material such as
vocals, wind instruments, strings, and so on. Overlaps are permitted—the pre-delayed start
point of a region can extend back to the end of the previous region—but only if the Threshold
value is not exceeded. The Pre Attack Time doesn’t affect the anchor position, which means the
absolute position of the audio data (in the project) is retained.
•
Post Release-Time: Use to define an automatic release time for the end points of all regions,
avoiding abrupt cutoffs to amplitudes that fade out gradually (particularly if you have set
a high Threshold value); for example, cymbals, open hi-hats, snares with long reverb tails,
vocals, and so on. This parameter does not allow overlaps, which means that region end
points cannot extend beyond the start point of the following region. The Post Release Time
doesn’t affect the anchor position, which means the absolute position of the audio data (in the
project) is retained.
•
Search Zero Crossings: Select this checkbox to automatically snap the region start and end
points to the nearest waveform zero crossings.