User`s manual

Page 27
samples and in milliseconds. Minimum Delay is 1 sample, but can be set to as
high as 2250 samples depending on the channel configuration.
Filter Output
Selects the output of the filter. The normal output, or “residue,” is the primary
signal that remains after the reference has been cancelled. The prediction, or
rejected output, is the part of the primary signal that is removed by the reference
canceller. This setting provides a way to hear what is being cancelled from the
signal. For most situations, the Normal output should be selected.
Adapt Mode
When Auto Adapt Mode is enabled, the specified Adapt Rate is continuously
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 used at all times
without 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 MicroDAC 5 is designed 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
changes suddenly, requiring a new filter solution; this may occur when the
microphone is moved, or when processing tape recorded conversations that
occurred at different locations.
6.2 1CH Filter
The 1CH Adaptive filter is used to automatically cancel predictable noises and
effects from the input audio. Predictable noises include tones, hum, buzz,
engine/motor noise, and, to some degree, music. Predictable effects include
echoes, reverberations, and room acoustics.