Azzera filtri
Azzera filtri

How to design a Butterworth filter?

7 visualizzazioni (ultimi 30 giorni)
Todd
Todd il 29 Giu 2012
It is going to be a two-pole low-pass Butterworth filters with a nominal cutoff frequency of 15 Hz.
An additional note is "calculated breakpoint frequencies are 18 Hz and 19 Hz for the first and second pole respectively" not sure if this info is necessary

Risposte (1)

Yash
Yash il 30 Giu 2012
Modificato: Walter Roberson il 1 Lug 2012
i developed this code for my program, it may help you
a=wavread('1.wav');
ah=a.*hann(length(a));
aN=length(ah);
indexa=[0:1:aN-1];
fs=8000;
fa=[0:1:aN-1]*fs/aN;
aff=abs(fft(ah))/aN;
figure % for siren 1
plot (fa,aff);
xlabel(' FFT of Siren 1');
n = 1; % Filter order
lf = .5e3; % low frequency cutoff for bandpass
hf = 1.5e3; % high frequency cutoff for bandpass
[b,a] = butter(n, [lf hf]/(fs/2));
fout = filter(b,a,ah);
% Plot Spectrum figure
spec = fft(fout,nfft);
pfspec = spec(1:fix(nfft/2)); % Extract postive frequencies
plot(pfax/1e3,abs(pfspec))
xlabel('Hz')
ylabel('Magnitude')
title('Filter Signal Spectrum ')

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