Updated November 10, 2013
Comb filtering is produced by mixing a delayed copy of the signal back into itself. The signal is delayed only briefly, so no echo is heard; instead, frequencies with wave periods that divide evenly into the delay time are reinforced, while others are attenuated. Graphing the amplitude of the filter output against frequency yields a comb shape that gives the filter its name. The result is a chilly, reverberant sound that emphasizes certain notes and dampens others.
After setting the effect type to Comb filter, you will see the following controls:
TRACK EFFECTS dialog with Comb filter effect
|FREQ||Sets the length of the comb filter delay so as to target the specified frequency. When FEED is positive, integer multiples of FREQ will be strengthened, and frequencies between those multiples will be attenuated; when FEED is negative, this relationship will be reversed, so integer multiples are attenuated, while frequencies between multiples are strengthened. When pitched sounds are played, this effect will cause certain notes to ring loudly while dampening others.|
|FEED||Sets the amount of the delayed signal to be fed back to the delay. Values farther from zero produce stronger filtering, and increase the resonant qualities of the effect. Large positive or negative values can produce loud ringing effects, so take care when setting this parameter.|
|POST||Sets the post-effect level, in percent. Filter resonance can produce loud tones; by adjusting POST, you can moderate such output without changing synthesis or loop element settings.|