User`s manual

22
7.5 Bandstop Filter
Application:
The Bandstop filter is used to decrease the energy level (lower the volume) of all signal
frequencies above a specified Lower Cutoff Frequency and below a specified Upper Cutoff
Frequency. The signal region between the Lower Cutoff Frequency and the Upper Cutoff
Frequency is called the stopband region. The Bandstop filter is useful for removing in-band noise
from the input signal.
The Lower Cutoff Frequency is usually set below the frequency range of the noise, while the
Upper Cutoff Frequency is set above the frequency range of the noise. While listening to the filter
output audio, the Lower and Upper Cutoff Frequencies can be incrementally adjusted to achieve
maximum elimination of noise while minimizing loss of voice.
The amount of volume reduction in the stopband region 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 each Cutoff Frequency) to the minimum volume (specified by
Stopband Attenuation) can also be controlled by adjusting the Transition Slope setting.
Figure 7-8: Bandstop Filter Control Window
Description of controls is as follows:
Lower Cutoff Specifies frequency in Hertz below which no
Frequency: signals are attenuated. Frequencies between this cutoff and the Upper Cutoff
Frequency are attenuated. Minimum Lower Cutoff Frequency is 0 Hz, while the
maximum Lower Cutoff Frequency is 100 Hz below the Upper Cutoff Frequency.
Lower Cutoff Frequency can be adjusted in 1 Hz steps.
NOTE: The Lower Cutoff Frequency can never be set higher than 100 Hz below
the Upper Cutoff Frequency.
Upper Cutoff Specifies frequency in Hertz above which no
Frequency: signals are attenuated. Frequencies between this cutoff and the Lower Cutoff
Frequency are attenuated. Minimum Upper Cutoff Frequency is 100 Hz above
the Lower Cutoff Frequency, while the maximum Upper Cutoff Frequency is 5400
Hz. Upper Cutoff Frequency can be adjusted in 1 Hz steps.
NOTE: The Upper Cutoff Frequency can never be set lower than 100 Hz above
the Lower Cutoff Frequency.
Transition Specifies slope at which frequencies above the
Slope: Lower Cutoff Frequency and below the Upper Cutoff Frequency are attenuated in
dB per octave. Sharpest attenuation occurs when Transition Slope is set to
maximum, while gentlest attenuation occurs when Transition Slope is set to
minimum. Note that the indicated value changes depending upon Cutoff