User`s manual

Notch Limit: Specifies frequency in Hertz above which no notches are generated. Minimum

Notch Limit is 2 and 1/2 times the Fundamental Notch Frequency, while the

maximum Notch Limit setting is 5400 Hz. Notch Limit is adjustable in 1 Hz steps.

Notch Depth: Depth of notches that are generated. Notch Depth is adjustable from 0 dB to 90

dB in 1 dB steps.

Notch Harmonics: Specifies whether notches will be generated at All, Odd, or Even multiples, or

harmonics, of the Comb Frequency. If, for example, the Comb Frequency is set

to 60.000 Hz, then selecting All will generate notches at 60 Hz, 120 Hz, 180 Hz,

240 Hz, 300 Hz, etc. Selecting Odd will generate notches at 60 Hz, 180 Hz, 300

Hz, etc. Selecting Even will generate notches at 120 Hz, 240 Hz, 360 Hz etc.

Hint: In most instances, Odd will be sufficient to remove all hum harmonics.

A graphical description of the Comb filter and its controls follows in the figure below.

Figure 7-11: Comb Filter Graphical Description

7.7 Notch Filter

Application:

The Notch filter is used to remove, or "notch out", a narrow-band noise, such as a tone or a

whistle, from the input audio with minimal effect to the remaining audio. The Notch filter works

best with stable noise sources which have constant frequency; if the frequency of the noise

source varies, then the 1CH Adaptive filter is recommended.

To properly utilize the Notch filter, you will first need to identify the frequency of the noise; this is

best done using a Spectrum Analyzer.

Initially set the Notch Depth to 90 dB and the Notch Width to the narrowest possible value. Next,

set the Notch Frequency to the noise frequency. Fine adjustment of the Notch Frequency may be

necessary to place the notch precisely on top of the noise signal and achieve maximum reduction