Code showing error how to correct the code?

 The code given below,
clear all;
close all;


 [x,fs1]=audioread('cryrumble.wav');
%     ts1=1/fs1;
%     N1=length(x);
%     Tmax1=(N1-1)*ts1;
%     fsu=fs/(N-1);
%     t=(0:ts:Tmax);
%     f=(-fs/2:fsu:fs/2);
%     figure, subplot(411),plot(t,x),xlabel('Time'),title('Original Speech');
%     subplot(412),plot(f,fftshift(abs(fft(x)))),xlabel('Freq (Hz)'),title('Frequency Spectrum');
%       fs2 = (20/441)*fs1;
%   na=resample(audio,2000,44100);
%   N2=length(na);
 ts1=1/fs1;
    N1=length(x);
    Tmax1=(N1-1)*ts1;
    t1=(0:ts1:Tmax1);
    figure;
  plot(t1,x),xlabel('Time'),title('Original audio');
  fs2 = (20/441)*fs1;
 na=resample(x,2000,44100);
%sound(y,fs2);
   ts2=1/fs2;
   N2=length(na);
   Tmax2=(N2-1)*ts2;
   t2=(0:ts2:Tmax2);
   fsu=fs2/(N2-1);
   f=(-fs2/2:fsu:fs2/2);


% Step 1: Pre-Emphasis

a=[1];
    b=[1 -0.95];
    y=filter(b,a,na);
    subplot(413),plot(t2,y),xlabel('Time'),title('Signal After High Pass Filter - Time Domain');
    subplot(414),plot(f,fftshift(abs(fft(y)))),xlabel('Freq (Hz)'),title('Signal After High Pass Filter - Frequency Spectrum');
% Step 2: Frame Blocking

     frameSize=882;

frame_duration=0.025;
frame_len = frame_duration*fs2;
framestep=0.01;
framestep_len=framestep*fs2;
num_frames =floor(N2/frame_len);

frames=[];
for j=1:num_frames
     frame=na((j-1)*framestep_len + 1: ((j-1)*framestep_len)+frame_len);

max_val=max(frame);
   if (max_val>0.025)

        frames=[frames;frame'];
   end
end
% Step 3: Hamming Windowing

NumFrames=size(frames,1);
hamm=hamming(frame_len)';
windowed=[];
    for i=1:NumFrames
    windowed(i,:)=frames(i,:).*hamm;
    end
    % Step 4: FFT 


    for i=1:NumFrames
    ft(i,:)=abs(fft((windowed(i,:)),frame_len));     
    plot(ft(i,:))
    end
    
% Step 5: Mel Filterbanks
Lower_Frequency =100;
Upper_Frequency = fs2/2;
    Nofilters=20;
    lowhigh=[100 fs2/2];
    %Here logarithm is of base 'e'
    lh_mel=1125*(log(1+lowhigh/700));
    mel=linspace(lh_mel(1),lh_mel(2),Nofilters+2);
    figure;
    plot(mel);
    xlabel('frequency in Hertz');ylabel('mels');
    title('melscale');
    melinhz=700*(exp(mel/1125)-1);
    %Converting to frequency resolution
    fres=floor(((frameSize)+1)*melinhz/fs2); 
    %Creating the filters
    for m =2:length(mel)-1
        for k=1:frameSize/2
     if k<fres(m-1)
        H(m-1,k) = 0;
    elseif (k>=fres(m-1)&&k<=fres(m))
        H(m-1,k)= (k-fres(m-1))/(fres(m)-fres(m-1));
    elseif (k>=fres(m)&&k<=fres(m+1))
       H(m-1,k)= (fres(m+1)-k)/(fres(m+1)-fres(m));
    elseif k>fres(m+1)
        H(m-1,k) = 0;    
     end 
        end
    end
        %H contains the 20 filterbanks, we now apply it to the
    %processed signal.
    for i=1:NumFrames
    for j=1:Nofilters
        bankans(i,j)=sum((ft(i,:).*H(j,:)).^2);
    end
    end
     figure;
    plot(H);
    xlabel('Frequency');ylabel('Magnitude');
    title('Mel-Frequency Filter bank');
    % Step 6: Nautral Log and DCT

%     pkg load signal
    %Here logarithm is of base '10'
    logged=log10(bankans);
    for i=1:NumFrames

        mfcc(i,:)=dct2(logged(i,:));
    end
    %plotting the MFCC
    figure 
    hold on
    for i=1:NumFrames
        plot(mfcc(i,1:13));
    end
    hold off
% save c5 mfcc

i= mfcc;
save i i

The code showing the error like this,

Matrix dimensions must agree.

Error in mfccc (line 111)

bankans(i,j)=sum((ft(i,:).*H(j,:)).^2);

How to rectify this error?

Answer 1

[Anudeep Kumar]

Hey Suchitra,

After running your code once I found out the error you are encountering is due to a size mismatch in your element-wise multiplication. The number of columns of the variable “ft” and “H” do not match.

• “ft(i,:)” is a 1xm vector.
• “H(j,:)” is a 1xn vector.

Element-wise multiplication of these two vectors is not possible because they have different dimensions.

You need to ensure that the vectors you are trying to multiply have the same length. Here is something you can try:

Adjust the Size of "H": Ensure that "H" has the same number of columns as "ft" . If "H" is supposed to be a filter bank, then it should match the number of columns in "ft".

Or

Modify the Code: If "H" is meant to process segments of "ft", adjust your code to handle segments correctly.

Here's an example if you meant to apply a filter to each segment:

for i = 1:NumFrames
    for j = 1:Nofilters
        % Adjust this part to select the correct segment of H
        % Assuming H is a filter to be applied to each row of ft
        % and should have the same length as ft
        if size(H, 2) == size(ft, 2)
            bankans(i, j) = sum((ft(i, :) .* H(j, :)).^2);
        else
            error('H must have the same number of columns as ft');
        end
    end
end

Here is a documentation on how element-wise multiplication works in MATLAB:

https://www.mathworks.com/help/releases/R2024b/matlab/ref/double.times.html

I hope this helps!