User`s manual

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4.4.3: 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 60dB). 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 4-19 Lowpass Filter Control Window