Vectors must be the same length

Hello, im having the error Vectors must be the same length for the code below:

%% An example of noise removal from an audio file

clearvars;

close all;

%% Read in the file

[f, Fs] = audioread('handel_J.wav');

T = 1 / Fs; % Sampling period

L = length(f); % Length of signal

t = (0:L-1) * T; % Time vector

%% Plot audio channels

N = size(f, 1);

figure; stem(t, f);

title('Original: Time-domain'); xlabel('time(seconds)');

%% Plot the spectrum

df = Fs / N;

w = (-(N/2):(N/2)-1)*df;

y = fft(f) / N; % For normalizing

y2 = fftshift(y);

figure; plot(w, abs(y2));

title('Original: Amplitude Spectrum'); xlabel('Frequency(Hz)');

%% plot the single-sided amplitude spectrum

figure;

plot(Fs*(0:(L/2))/L, abs(y2(N/2:end)))

title('Original: Single-Sided Amplitude Spectrum')

xlabel('f (Hz)')

%% find f1

% [fmax1, f1index] = max(abs(y2(N/2:end)));

% fmax1, f1index = f1index*df

%% filtering f1: 1043Hz

n = 2;

beginFreq = 1040 / (Fs/2);

endFreq = 1050 / (Fs/2);

[b,a] = butter(n, [beginFreq, endFreq], 'stop');

fOut = filter(b, a, f);

% extract f1

[b,a] = butter(n, [beginFreq, endFreq], 'bandpass');

f1 = filter(b, a, f);

figure; plot(w,abs(fftshift(fft(f1)/N))); title('f1: 1043Hz');

%% find f2

% [fmax2, f2index] = max(abs(fftshift(fft(fOut)/N)));

% fmax2, f2index = Fs/2 - f2index*df

%% filtering f2: 1956Hz

n = 2;

beginFreq = 1950 / (Fs/2);

endFreq = 1960 / (Fs/2);

[b,a] = butter(n, [beginFreq, endFreq], 'stop');

fOut = filter(b, a, fOut);

% extract f2

[b,a] = butter(n, [beginFreq, endFreq], 'bandpass');

f2 = filter(b, a, f);

figure; plot(w,abs(fftshift(fft(f2)/N))); title('f2: 1956Hz');

%% For normalizing

Ym = max(max(max(fOut)),max(abs(min(fOut))));

fOut = fOut ./ Ym;

%% After processing

figure; stem(t, fOut);

title('After processing: Time-domain'); xlabel('time(seconds)');

figure; plot(w,abs(fftshift(fft(fOut)/N)));

title('After processing: Amplitude Spectrum'); xlabel('Frequency(Hz)');

%% Create object for playing audio

pOrig = audioplayer(f,Fs); % original signal

% pOrig.play;

p = audioplayer(fOut, Fs); % filtered signal

% p.play;

pf1 = audioplayer(f1, Fs); % noise: f1: 1043Hz

% pf1.play;

pf2 = audioplayer(f2, Fs); % noise: f2: 1956Hz

% pf2.play;

%% Write out to audio file

audiowrite('handel_J_processed.wav', fOut, Fs);

audiowrite('f1.wav',f1,Fs);

audiowrite('f2.wav',f2,Fs);

Answer 1

[Star Strider]

I can’t run the code, however I believe the problem is with the legth of ‘w’ (since the call that threw that error is not stated). The time vectors appear to be correct, so I doubt those plots are throuwing the error.

For two-sided fft plots using fftshift, I usually define the frequency vector as going from the negative Nyquist frerquency to the positive Nyquist frequency with the vector length equal to the length of the fft argument. That ’s just easier.

w = linspace(-Fs/2, Fs/2, L);

That should work, and should solve the unequal vector lengths problem.

.

[Nathan Espindola]

The error is at line 27 and the audio file is attach.

I still coudnt find the problem.

[Star Strider]

The frequency vector and amplitude length mismatch were the problem.

Try this —

uz = unzip('https://www.mathworks.com/matlabcentral/answers/uploaded_files/805604/handel_J.zip')

uz = 1×1 cell array
    {'handel_J.wav'}

uzv = uz{1}

uzv = 'handel_J.wav'

[f,Fs] = audioread(uzv)

f = 354221×2

1.0e+00 * 0 0 0 -0.0000 0.0000 0.0001 -0.0000 -0.0000 0.0000 0.0000 0 0 0 0 0.0000 0 -0.0000 0.0000 0.0001 0

Fs = 44100

T = 1 / Fs;             % Sampling period
L = length(f);          % Length of signal
t = (0:L-1) * T;        % Time vector
%% Plot audio channels
N = size(f, 1);
figure;  stem(t, f);
title('Original: Time-domain');  xlabel('time(seconds)');

%% Plot the spectrum
df = Fs / N;
% w = (-(N/2):(N/2)-1)*df;
w = linspace(-Fs/2, Fs/2, L);
y = fft(f) / N;         % For normalizing
y2 = fftshift(y);
figure;  plot(w, abs(y2));
title('Original: Amplitude Spectrum');  xlabel('Frequency(Hz)');

%% plot the single-sided amplitude spectrum
figure;
% plot(Fs*(0:(L/2))/L, abs(y2(N/2:end)))

w1 = linspace(0, 1, fix(L/2)+1);
Iv = 1:numel(w1);
plot(w1, abs(y(Iv))*2)
title('Original: Single-Sided Amplitude Spectrum')
xlabel('f (Hz)')

%% find f1
% [fmax1, f1index] = max(abs(y2(N/2:end)));
% fmax1, f1index = f1index*df
%% filtering f1: 1043Hz
n = 2;
beginFreq = 1040 / (Fs/2);
endFreq = 1050 / (Fs/2);
[b,a] = butter(n, [beginFreq, endFreq], 'stop');
fOut = filter(b, a, f);
% extract f1
[b,a] = butter(n, [beginFreq, endFreq], 'bandpass');
f1 = filter(b, a, f);
figure;  plot(w,abs(fftshift(fft(f1)/N)));  title('f1: 1043Hz');

%% find f2
% [fmax2, f2index] = max(abs(fftshift(fft(fOut)/N)));
% fmax2, f2index = Fs/2 - f2index*df
%% filtering f2: 1956Hz
n = 2;
beginFreq = 1950 / (Fs/2);
endFreq = 1960 / (Fs/2);
[b,a] = butter(n, [beginFreq, endFreq], 'stop');
fOut = filter(b, a, fOut);
% extract f2
[b,a] = butter(n, [beginFreq, endFreq], 'bandpass');
f2 = filter(b, a, f);
figure;  plot(w,abs(fftshift(fft(f2)/N)));  title('f2: 1956Hz');

%% For normalizing
Ym = max(max(max(fOut)),max(abs(min(fOut))));
fOut = fOut ./ Ym;
%% After processing
figure;  stem(t, fOut);
title('After processing: Time-domain');  xlabel('time(seconds)');

figure;  plot(w,abs(fftshift(fft(fOut)/N)));
title('After processing: Amplitude Spectrum');  xlabel('Frequency(Hz)');

Success!

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