biquad to filter out unwanted signal ?

    Dec 27 2006 | 9:43 pm
    I have seen some people use biquad object at the audio input to filter out unwanted noises or frequency to avoid mistakes for pitch tracking. However, I never understand how they know those parameters for biquad.
    Is it a try-and-error thing? Are there some good tutorials I should study first before I can figure out the parameters for biquad~ to help improve the precision of pitch tracking ?
    Take the example of using biquad for better pitch tracking result. What is the usual process of finding the biquad parameters ?
    Please share your experiences.