How to remove multiple evenly spaced frequency components from digital signal

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Fan Yang
Fan Yang on 15 Nov 2021
Commented: Mathieu NOE on 15 Nov 2021
Hey guy,
the FFT of my acustic signal returned some evenly spaced back group noisey frequencies 3,6,9,12,15hz. To remove them at once, I beliebe I can use a irrnotch or irrcomb. But the example of both functions only demonstrated how to remove a signal frequency component, which is a 60hz notch. I am wondering how can I remove multiple evenly spaced frequency components at once.
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Mathieu NOE
Mathieu NOE on 15 Nov 2021
iircomb will do the job for multiple frequencies - read again the help . yes it will remove the 60 hz tone plus all harmonics
example is given for 11 notches = 60 Hz tone + 10 harmonics will be removed
Design and plot an IIR notch filter with 11 notches (equal to filter order plus 1) that removes a 60 Hz tone (f0) from a signal at 600 Hz(fs). For this example, set the Q factor for the filter to 35 and use it to specify the filter bandwidth.
fs = 600;
fo = 60;
q = 35;
bw = (fo/(fs/2))/q;
[b,a] = iircomb(fs/fo,bw,'notch'); % Note type flag 'notch'

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