MicroDAC 5 User's Manual - Digital Audio Corporation

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When the MicroDAC 5 is running standalone (not connected to the PC), the filterruns at whatever settings are stored in the nonvolatile memory. When runningconnected to the PC, finer control is available. Figure 6-2 shows the filtercontrols available for the 1CH adaptive filter.Figure 6-2: 1CH Filter DialogDescription of the controls pictured in Figure 6-2 follows:Filter SizeUsed to set the number of FIR filter taps in the adaptive filter. Filter size isindicated both in taps (filter order) and in milliseconds. Minimum Filter Size is 16taps, but can be set to as high as 2048 taps depending on the system bandwidth.Small filters are most effective with simple noises such as tones and music.Larger filters should be used with complex noises such as severe reverberationsand raspy power hums.Adapt RateUsed to set the rate at which the adaptive filter adapts to changing signalconditions (mathematically known as Mu). A Mu of 1 x 2 -18 provides very slowadaptation, while a Mu of 5884 x 2 -18 provides fastest adaptation.Page 28
Slower adapt rates take longer to reach a solution or to adapt to changing signalcharacteristics, but a slow rate is still quite effective for stable tones andreverberations and slow adapt rates make filter crashes less likely. Faster adaptrates may be required for changing noises, but a fast adapt rate can also affectthe quality of the target speech as the filter may attack sustained vowel sounds.Prediction SpanSets the number of samples in the prediction span delay line. Prediction span isindicated both in samples and in milliseconds, and can be adjusted from 1 to 64samples. Shorter prediction spans allow maximum noise removal, while longerprediction spans preserve voice naturalness and quality. A prediction span of 2or 3 samples is normally recommended.Filter OutputUsed to select the output of the filter. The Normal output, or “residue,” is thesignal that remains after predictable noises have been removed. The Prediction(rejected) output contains the predictable noise that is removed. The Predictionsetting isn’t typically used in normal operation, but it allows you to hear the noisethat the filter is removing, which can be useful when configuring the filter settings.For most situations, the Normal output should be selected.Adapt ModeWhen Auto Adapt Mode is enabled, the specified Adapt Rate is continuouslypower scaled based upon the input signal level. This generally results in fasterconvergence for a given adapt rate setting without greatly increasing the risk of afilter crash. When Fixed is selected, the specified Adapt Rate is utilized at alltimes without power scaling. Auto is the recommended setting.Enable Crash DetectWhen checked, enables the Crash Detect algorithm in the MicroDAC 5.Coefficients of adaptive filters have the potential of diverging instead ofconverging; this is most likely to happen for faster adapt rates or when there is aquick 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 becomesdistorted. Since the MicroDAC 5 is meant for unmanned deployment, a filtercrash would be unacceptable. A good choice of adapt rate coupled with the Autoadapt mode should make crashes extremely rare, but with Crash Detectionenabled the filter will automatically detect any crash and then clear the filter so itcan reconverge to a good solution.Clear Filter SolutionThe Clear Filter Solution button is used to restart the adaptive filters as deemednecessary. This function is sometimes used in the case of a filter crash, althoughthis use should be unnecessary if Crash Detection is enabled. Another exampleof when to press the Clear Filter Solution button is when the audio scenePage 29
Page 1: Multi-Channel Reference CancellerUS
Page 7: 1 Overview1.1 IntroductionMicroDAC
Page 11: 3 Standalone ControlsControls on th
Page 14 and 15: 3.1.4.5 Clear FiltersUse the CLEAR
Page 16 and 17: Audio Output (1):o TOSLINK optical
Page 18 and 19: 5.3 FiltersFour different filters a
Page 20 and 21: Figure 5-3: Mono sub-menuIn mono mo
Page 22 and 23: Figure 5-6: Mono 4CH5.6.2 Stereo Co
Page 25 and 26: 5.6.3 Audio Line Out ConfigurationB
Page 27 and 28: are stored in nonvolatile memory on
Page 29 and 30: they are “out.” Taking one of t
Page 31 and 32: 6 FiltersTo configure a specific fi
Page 33: samples and in milliseconds. Minimu
Page 37 and 38: Figure 6-4: Automatic Gain Control
Page 39 and 40: 7 InstallationTo install the MicroD
Page 41 and 42: 3. After the .NET install completes
Page 43 and 44: 7. Next, before running the MicroDA
Page 45 and 46: d. Once the driver has finished ins
Page 47 and 48: 3. You will be presented with a “
Page 49 and 50: 7. You may see another “unidentif

MicroDAC 5 User's Manual - Digital Audio Corporation

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