User`s manual

25
of the noise. This is best done by adjusting the Notch Frequency up or down 1 Hz at a time while
listening to the Notch filter output on the headphones.
Often, the noise frequency will not remain absolutely constant but will vary slightly due to
modulation, recorder wow and flutter, and acoustic "beating." Therefore, you may need to
increase the Notch Width from its minimum setting to keep the noise within the notch.
For maximum noise reduction, set the Notch Depth to 90dB. It is best to adjust the Notch Depth
up from 90 dB until the tone is observed, then increase the depth 5 dB.
Figure 7-12: Notch Filter Control Window
Description of controls is as follows:
Notch Frequency: Specifies frequency in Hertz which is to be removed from the input audio.
Minimum Notch Frequency is 0 Hz, while maximum Notch Frequency is 5400 Hz.
Notch Frequency is adjustable in 1 Hz steps.
Notch Depth: Depth of the notch that is generated. Notch Depth is adjustable from 0dB to
90dB in 1 dB steps.
Notch Width: Width of the generated notch in Hertz.
Hint: A notch filter works best for stable tones. It has a sharp bottom. If a flatter bottom
(stopband) is needed to accommodate some variation in tone frequency, the bandstop filter may
be prefered. Also, a 1CH Adaptive filter is useful in tracking varying tones.
A graphical description of the Notch filter and its controls follows in the figure below..
Figure 7-13: Notch Filter Graphical Description
7.8 Slot Filter
Application:
The Slot filter is used to isolate, or "slot", a single-frequency signal, such as a tone or a whistle, in
the input audio, attenuating all other audio. This is the exact opposite of the Notch filter function.