How do I read and split an audio file into four different frequency ranges?

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sangeet sagar 2018-9-14

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评论： Star Strider 2018-9-17

I have an audio file of sampling frequency as 16 kHz. Now I would like to read it and split its samples into four range. Namely:

kHz - 1 kHz
kHz - 2 kHz 
kHz - 4 kHz
kHz - 8 kHz

I have come about the following code but I am not sure if it is correct? I wanted to know if there is any other way.

[signal,fs]=audioread('003.wav');
SigFD = (signal);
n = length(signal); % number of samples
deltaF = fs/n; % frequency resolution
F = [0:floor(n/2)-1, -(floor(n/2)):-1]*deltaF; % frequency vector
lowF = 0; % lowF and highF defines one of the range
highF = 1000;
part1Range = abs(F)>lowF&abs(F)<highF;
Fpart1 = F(part1Range);
Sig1FD = SigFD(part1Range);

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Answer 1

Star Strider 2018-9-14

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If you have R2018a or later, use the bandpass (link) function on your original signal, each with different passband limits.

If you have an earlier version, use ellipord (link) and ellip (link), that together are almost as easy.

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sangeet sagar 2018-9-17

Could you please suggest how to do it MATLAB 2015 using ellipord?

Thank You

Star Strider 2018-9-17

在 MATLAB Online 中打开

As always, my pleasure.

The first filter is a simple lowpass filter with a passband a 1 kHz. You can use this prototype code to design it.

This designs the second filter:

Fs = 1.6E+4;                                                % Sampling Frequency (Hz)
Fn = Fs/2;                                                  % Nyquist Frequency (Hz)
Fnotch = 1.5E3;                                             % Notch Frequency (Hz)
BW = 1E+3;                                                  % Passband Width (Hz)
Ws = [Fnotch-BW/2-1 Fnotch+BW/2+1]/Fn;                      % Passband Frequency Vector (Normalised)
Wp = [Fnotch-BW/2-5 Fnotch+BW/2+5]/Fn;                      % Stopband Frequency Vector (Normalised)
Rp =   1;                                                   % Passband Ripple (dB)
Rs = 150;                                                   % Stopband Attenuation (dB)
[n,Wp] = ellipord(Wp,Ws,Rp,Rs);                             % Default Here Is A Bandpass Filter
[z,p,k] = ellip(n,Rp,Rs,Wp);
[sos,g] = zp2sos(z,p,k);                                    % Use Second-Order-Section Implementation For Stability
% s_filtered = filtfilt(sos,g,s);                             % Filter Signal (Here: ‘s’)
figure
freqz(sos, 2^14, Fs)                                        % Bode Plot Of Filter
set(subplot(2,1,1), 'XLim',[0 Fn])                          % Optional, Change Limits As Necessary For Best Resolution
set(subplot(2,1,2), 'XLim',[0 Fn])                          % Optional, Change Limits As Necessary For Best Resolution