Autodesk 64006-051108-9001 - Discreet Cleaner - Mac, Руководство пользователя

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Chapter 6: Pre-processing 82
Unlike the Noise Removal, Notch, High Pass and Low Pass filters, which remove specific
frequencies throughout the whole length of the source, the Noise Gate totally silences the entire
signal when it goes below a certain volume (amplitude) for a specific amount of time, such as
between words or sentences in speech.
Generally, the Noise Reduction/Notch filters should be used first and the Noise Gate added if
there is still noticeable noise in areas that should be silent.
Note:
You should not use the Noise Gate with material which has a background sound track, or
other continuous sound. This filter is only useful with material that has sections that should be
totally silent.
Custom Noise Gate
The Custom Noise Gate setting has two controls. The Threshold controls the level under which
the Noise Gate totally silences the audio track. The higher the setting, the louder the sections
the Noise Gate silences.
If you set the Threshold too high, the Noise Gate can remove meaningful parts of the audio,
which can sound very odd. For example, quieter parts of the narration may get silenced. If you
set it too low, the Noise Gate may never activate, and the audio is not altered.
The Minimum Duration controls how long a quiet section must last before the Noise Gate
silences it. Setting this to a very short duration can cause narration to get choppy as the Noise
Gate silences spaces between words or syllables.
Notch
The Notch filter removes a group of frequencies centered on a specified frequency. Whereas the
High and Low Pass filters eliminate frequencies at the ends of the audio spectrum, this filter
removes a notch of frequencies in the middle. This is often useful for removing a specific
offending frequency, such as AC power line noise. Line noise is generally 60 Hz in the U.S., 50
Hz in Europe.
The preset options relate to common power line frequencies. If your source suffers from line
noise, try one of these settings first. If you are unable to effectively remove the line noise with
the preset, or if your source has different frequency noise, the Custom option may be helpful.