Apple Logic Pro 9 - Manual (Page 585)

Applying Spike Reduction in the Silencer
The aim of Spike Reduction is to identify and reduce signals such as pops, clicks, or digital
spikes, in order to reconstruct a hypothetical original signal. You use the following
parameters to do this.
Note: When you are applying Spike Reduction, it is recommended that you turn off the
Noise Reduction function. This ensures that only the Spike Reduction function is used.
• Sensitivity slider: Determines the threshold level used for the recognition of spikes in
the audio file.
• Off: No edits will occur.
• Auto: Threshold is controlled automatically.
• Low: Most signal peaks are identified as spikes.
• High: Relatively small signal spikes are identified.
Note: You may need to experiment with the parameters. If the Sensitivity slider is set
to High (or close to it), there’s a danger that very sharp transients in the main signal
will be identified as spikes. Depending on the audio material, it’s sometimes impossible
for the Silencer to distinguish between signals you want to keep and signals you want
to eliminate. This is particularly the case if the decision between spike or main signal
is merely a matter of taste—with some click-like bass drum sounds, for example. The
attack phase of these sounds can have similar characteristics to static on vinyl records.
• Method slider: Determines how the identified spike points in the original signal are
processed.
• Gentle: Weakest algorithm, only slightly smoothing the original signal.
• Aggressive: Strongest algorithm, with a very noticeable impact on the audio.
• Re-build: Replaces the (often unusable) original signal with an artificially generated
estimate of the original signal, at the identified points. This synthesized signal is
created by analyzing the audio material surrounding these points.
Applying Noise Reduction in the Silencer
The purpose of Noise Reduction is to reduce the noise components of the signal, and
also to affect the main signal, particularly the high frequency elements.
585 Chapter 17 Editing Audio in the Sample Editor