User`s manual

26
To properly utilize the Slot filter, you will first need to identify the frequency of the signal to be
isolated; this is best done using a Spectrum Analyzer.
Once the frequency of the signal has been identified, initially set Stopband Attenuation to 90 dB
and the Slot Width to the narrowest possible value. Next, set the Slot Frequency to the signal
frequency. Fine adjustment of the Slot Frequency may be necessary to place the slot right on top
of the signal. This is best done by adjusting the Slot Frequency up or down 1 Hz at a time while
listening to the Slot filter output on the headphones.
Usually, the signal frequency will not remain constant but will vary slightly due to modulation,
recorder wow and flutter, and acoustic "beating". Therefore, you may need to increase the Slot
Width from its minimum setting to avoid having the signal move in and out of the slot.
Figure 7-14: Slot Filter Control Window
To optimize background noise reduction for your application, set the Stopband Attenuation to
60dB. If, however, you wish to leave a small amount of the background noise mixed in with the
isolated signal, adjust the Stopband Attenuation to the desired value.
Description of controls is as follows:
Slot Frequency: Specifies frequency in Hertz which is to be enhanced in the input audio.
Minimum Slot Frequency is 30 Hz, while maximum Slot Frequency is 5400 Hz.
Slot Frequency is adjustable in 1 Hz steps.
Stopband Specifies amount in dB by which frequencies
Attenuation: other than the Slot Frequency are attenuated. Stopband attenuation is
adjustable from 0dB to 90dB in 1 dB steps.
Slot Width: Width of the generated slot in Hertz.
A graphical description of the Slot filter and its controls follows in the figure below. Note that the slot
width is defined at its -6 dB points.
Figure 7-15: Slot Filter Graphical Description