User`s manual

53
Click on the Clear button if you desire the filter to completely
readapt based upon the new Conditional Adaptation settings.
The Adapting LED indicator shows the current adaptation status of
the filter; if the LED is illuminated GREEN, the filter is adapting, and
when the LED is not illuminated the filter is not adapting. In Stereo,
Linked Input Mode, only the Left channel adaptation status is
displayed.or GRAY when the filter is frozen. In Stereo, Linked
configuration, two indicators are provided for each filter block (one
LED for each channel).
Filter Size: Used to set the number of FIR filter taps in the adaptive filter. Filter size
is indicated both in taps (filter order) and in milliseconds. Minimum
Filter Size is 4 taps, but can be set to as high as 6144 taps depending on
System Bandwidth, Input Mode, and Number of General Filter Stages
settings.
Small filters are most effective with simple noises such as tones and
music. Larger filters should be used with complex noises such as severe
reverberations and raspy power hums. A nominal filter size of 512 to
1024 taps is a good overall general recommendation.
Adapt Rate: Used to set the rate at which the adaptive filter adapts to changing
signal conditions (mathematically known as Mu). A Mu of 1 x 2
-14
provides very slow adaptation, while a Mu of 3808 x 2
-14
provides
fastest adaptation.* As a rule set this rate to approximately 100-200
initially, to establish convergence, then back off to a mid value to
maintain cancellation.
Larger adapt rates should be used with changing noises such as music;
whereas, smaller adapt rates are acceptable for stable tones and
reverberations. Larger adapt rates sometimes affect voice quality, as
the filter may attack sustained vowel sounds.
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*2
-14
is a means of expressing 2 raised to the –14
th
power, which equals 0.000061; 256 x 2
-14
is, therefore, equal to
0.016.