How to right use awgn after audioread?

Hello,

I've already found some topics, but I still don't understand what's wrong.

I want to overlay x from audioread with a Gaussian white noise with different amplitudes

SNR = 20; %maximum value
[x,Fs] = audioread([fpath,fname],[st_smp,en_smp]); %read wav file 
    for i = 1:SNR %for any value from 1 to SNR
        test=x;   %save original from changing
        test = awgn(test,i);    %overlay with gaussian noise and SNR = 1 dB???
         
        anotherF()
        
        %figure
        hold on
        win = 2^round(log2(Fs)-3);
        win = win*4;
        step = round(win/8);
        specx = getspecx(test,Fs);
        myspec(test,Fs,win,step,win);
        ylim([0 1000]);
        xlabel('t_{seconds}')
        ylabel('Rotation 1/s')
      
        colormap jet
        save(FileSave, 'Traj');
        fig_name = [name,'_SNR_',num2str(i),'_PLL.png'];
        saveas(gcf, fig_name)
        movefile(FileSave,FilePath);
        movefile(fig_name,FilePath);
    end
%close all

But I got exactly the opposite of what I expected

from left to right i value in awgn(test,i); grows

why is this happened?

Have I do some transformation before?

Description says:

out = awgn(in,snr) adds white Gaussian noise to the vector signal in. This syntax assumes that the power of in is 0 dBW.

what is my snr value?

Answer 1

[Devineni Aslesha]

Hi Nik,

Here, the snr value increases by 1 dB for every for loop iteration. Since, some userdefined functions are used before saving the test data with added noise, I assume that the test data is being modified after overlaying it with the additive white gaussian noise.

I recommend you to check the reason for the test data being modified. However, plotting the test data after 'test = awgn(test,i);' line gives the correct results i.e. As snr increases, test data is with less noise power.