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I have done a fourier transform of some experimental data to calculate the dominant frequency of the vibration in a flow, but I get a spike at 1000, which is from interferences. How do I ignore or filter this frequency to get the right frequency distribution?

Matthew Simoneau
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Fran J
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    you can take a look at the answers to a [previous question on hi-pass filtering](http://stackoverflow.com/questions/5591278/high-pass-filtering-in-matlab). There is a lot of detail in them and you can simply change your pass-band from high pass to low pass to get the desired effect. –  Apr 18 '11 at 15:17
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    I would suggest designing a notch filter if you only need to remove a single frequency component – Phonon Apr 18 '11 at 15:54

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The easiest approach is probably to use the Matlab function iirnotch.

x = ; % Populate this with your input signal

fsHz = ; % Populate this with your sample rate
notchFreqHz = 1000; % The frequency you with to notch
notchWidthHz = 50; % Notch width (-3 dB bandwidth)

w0 = notchFreqHz / fsHz; % Normalized notch frequency
bw = notchWidthHz / fsHz; % Normalized bandwidth

[num,den] = iirnotch(w0, bw);

y = filter(num, den, x); % Apply the filter, y is the output signal

See Second-order IIR notch filter - MATLAB iirnotch for more details.

GrapefruitIsAwesome
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