MATLAB: Human voice frequency between 200h to 3200h

bandpass filterfrequency

i konw that the human voice frequency between 200 to 3200 H and i record wave file ,how can i filter this wave ile so only human voice (frequency between 200 to 3200) will stay in the wave file

for record i use

Fs = 8000;
      y  = wavrecord(10*Fs, Fs, 'double');

Best Answer

Let's say the passband is between 200 and 3200 Hz and the stop band is 100 and 3300 Hz, you can use a Butterworth filter

Ws = [100 3300]/(Fs/2);
Wp = [200 3200]/(Fs/2);
[N,Wn] = buttord(Wp,Ws,0.1,30);
[b,a] = butter(N,Wn);
filter(b,a,y)

If you want more options to design your filter, try fdatool

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You gave enough information for the Signal Processing Toolbox (with a bit of help from me) to be able to design your filter:

Fs  = 8000;                                 % Sampling Frequency (Hz)
Fn  = Fs/2;                                 % Nyquist Frequency
Fco =   20;                                 % Passband (Cutoff) Frequency
Fsb =   30;                                 % Stopband Frequency
Rp  =    1;                                 % Passband Ripple (dB)
Rs  =   10;                                 % Stopband Ripple (dB)
[n,Wn]  = buttord(Fco/Fn, Fsb/Fn, Rp, Rs);  % Filter Order & Wco
[b,a]   = butter(n,Wn);                     % Lowpass Is Default Design
[sos,g] = tf2sos(b,a);                      % Second-Order-Section For STability
figure(1)
freqz(sos, 2048, Fs)                         % Check Filter Performance

Then use the filtfilt function to filter your signal.

I chose a Butterworth design, but if you want a steeper cutoff, consider using a Chebychev design instead. You may want to experiment with the design to get the exact result you want with respect to your signal. See the relevant documentation for details.

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You need to use a notch filter. See: Remove the 60 Hz Hum from a Signal (link) for an example.

I prefer to design my own filters, so try this:

Fs = 44100;                                                 % Sampling Frequency (Hz)
Fn = Fs/2;                                                  % Nyquist Frequency (Hz)
Wp = ([-5 5]+2.2E+3)/Fn;                                    % Stopband Frequency (Normalised)
Ws = ([-10 10]+2.2E+3)/Fn;                                  % Passband Frequency (Normalised)
Rp =   1;                                                   % Passband Ripple (dB)
Rs =  50;                                                   % Stopband Ripple (dB)
[n,Ws] = cheb2ord(Wp,Ws,Rp,Rs);                             % Filter Order
[z,p,k] = cheby2(n,Rs,Ws,'stop');                           % Filter Design, Sepcify Bandstop
[sosn,gn] = zp2sos(z,p,k);                                  % Convert To Second-Order-Section For Stability
figure(3)
freqz(sosn, 2^16, Fs)                                       % Filter Bode Plot
filtered_signal = filtfilt(sosn, gn, original_signal);      % Filter Signal

Best Answer

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