User`s manual

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set the adapt rate to a high value. However, the goal of the ASIF is not
to remove transient noises, but rather to reshape the long-term spectral
envelope of the signal. If the adapt rate is too fast, the filter will respond
too quickly to transient audio characteristics, which will produce artifacts
in the output audio and will prevent the filter from settling on a good
average solution. For this reason, most applications will work best with
adapt rates at the low end of the available range. If you hear tonal
artifacts that come and go in the output audio, or if the filter trace display
coefficients seem to be changing rapidly, you probably need to reduce the
adapt rate.
Filter Operation: In this block, the user can select the operational mode of the filter. If the
filter is being used to correct spectral coloration, the Equalize Voice
mode should be selected. If the filter is being used to remove bandlimited
noise, the Attack Noise mode should be selected.
Note: The Filter Operation mode selection only affects the behavior of
the filter outside the range selected by the upper and lower limits. In
Equalize Voice mode, the frequency ranges outside the limits are
attenuated. In Attack Noise mode, the frequency ranges outside the
limits are left unaffected (subject to a transition region near the limits). If
the auto gain is disabled and the manual gain is set to 0 dB, frequencies
outside the limits and transition regions will be unaffected. However, if
gain is applied, the gain will be reflected over the entire frequency range.
See the section on Upper and Lower Voice Limits for more
information on selecting the range.
Note: Changing the filter operation mode does not require an adaptation
period to arrive at a “good” solution. Because a full average spectrum is
maintained regardless of the mode setting, the new mode takes effect
instantaneously in both the output audio and the display traces.
However, since the auto gain adapts based on the actual applied filter
with operational mode taken into account, there may be some adaptation
time required to reach a stable auto gain value after the mode is changed.
Output Shape: In this block, the user can select the target spectral shape that the filter
attempts to achieve. The ASIF has an inherent spectral flattening effect
on the audio. The selected spectral shape is applied to further reshape
the audio spectrum. The following output shapes are available:
• Flat – no additional shaping after ASIF flattening
• Pink -- 3 dB per octave rolloff above 100 Hz is applied in addition to
ASIF flattening
• Voice – 6 dB/octave rolloff above and below 500 Hz in addition to
ASIF flattening