User`s manual

Page 29
Slower adapt rates take longer to reach a solution or to adapt to changing signal
characteristics, but a slow rate is still quite effective for stable tones and
reverberations and slow adapt rates make filter crashes less likely. Faster adapt
rates may be required for changing noises, but a fast adapt rate can also affect
the quality of the target speech as the filter may attack sustained vowel sounds.
Prediction Span
Sets the number of samples in the prediction span delay line. Prediction span is
indicated both in samples and in milliseconds, and can be adjusted from 1 to 64
samples. Shorter prediction spans allow maximum noise removal, while longer
prediction spans preserve voice naturalness and quality. A prediction span of 2
or 3 samples is normally recommended.
Filter Output
Used to select the output of the filter. The Normal output, or “residue,” is the
signal that remains after predictable noises have been removed. The Prediction
(rejected) output contains the predictable noise that is removed. The Prediction
setting isn’t typically used in normal operation, but it allows you to hear the noise
that the filter is removing, which can be useful when configuring the filter settings.
For most situations, the Normal output should be selected.
Adapt Mode
When Auto Adapt Mode is enabled, the specified Adapt Rate is continuously
power scaled based upon the input signal level. This generally results in faster
convergence for a given adapt rate setting without greatly increasing the risk of a
filter crash. When Fixed is selected, the specified Adapt Rate is utilized at all
times without power scaling. Auto is the recommended setting.
Enable Crash Detect
When checked, enables the Crash Detect algorithm in the MicroDAC 5.
Coefficients of adaptive filters have the potential of diverging instead of
converging; this is most likely to happen for faster adapt rates or when there is a
quick and dramatic change in the input signal such as a sudden loud noise.
When the filter diverges, it is called a filter “crash” and the audio becomes
distorted. Since the MicroDAC 5 is meant for unmanned deployment, a filter
crash would be unacceptable. A good choice of adapt rate coupled with the Auto
adapt mode should make crashes extremely rare, but with Crash Detection
enabled the filter will automatically detect any crash and then clear the filter so it
can reconverge to a good solution.
Clear Filter Solution
The Clear Filter Solution button is used to restart the adaptive filters as deemed
necessary. This function is sometimes used in the case of a filter crash, although
this use should be unnecessary if Crash Detection is enabled. Another example
of when to press the Clear Filter Solution button is when the audio scene