User`s manual

rescaled depending upon the input signal level. Overall convergence rate is

faster with Auto.

Adapt Algorithm: Selects the adaptive algorithm to use when processing the audio. The Least

Absolute Value (LAV) algorithm offers faster, but less accurate convergence.

The Least Mean Square (LMS) algorithm does not converge as fast as the LAV,

but offers a more accurate convergence and better maintains the final solution.

Processor Used to select the output of the filter. The

Output: normal setting is Residue, as this is the processed audio with the predicted noise

signal removed. The Predict output is the predicted noise signal. For example, if

a 1CH Adaptive Filter was being used to remove a tone, the Processor Output

choice of Predict would output only the the subtracted tone.

Crash Detect: Activates the built-in “crash” detection feature in the MicroDAC IV. This feature

automatically detects when the adaptive filter has “crashed” and clears the filter.

Checking this box enables this feature.

7.2 Lowpass filter

Application:

The Lowpass filter is used to decrease the energy level (lower the volume) of all signal

frequencies above a specified Cutoff Frequency, thus reducing high-frequency noises, such as

tape hiss, from the input audio. The Lowpass filter is sometimes called a "hiss filter."

The Cutoff Frequency is usually set above the voice frequency range so that the voice signal will

not be disturbed. While listening to the filter output audio, the Cutoff Frequency can be

incrementally lowered from its maximum frequency until the quality of the voice just begins to be

affected, achieving maximum elimination of high-frequency noise.

The amount of volume reduction above the Cutoff Frequency can further be controlled by

adjusting the Stopband Attenuation setting (maximum volume reduction is 90dB). The slope at

which the volume is reduced from normal (at the Cutoff Frequency) to the minimum volume

(specified by Stopband Attenuation) can also be controlled by adjusting the Transition Slope

setting.

Figure 7-2: Lowpass Filter Control Window

Description of controls is as follows:

Cutoff Specifies frequency in Hertz above which all

Frequency: Signals are attenuated. Frequencies below this cutoff are unaffected. Minimum

Cutoff Frequency is 100 Hz, while the maximum Cutoff Frequency is 5400 Hz.

Cutoff Frequency can be adjusted in 1 Hz steps.