How to input noise during the audio transmission process ?

Hello everyone

I do audio compression with bit per sample variations like this:

[y,Fs]=audioread('water.wav');
audiowrite('testing.flac',y,Fs,'BitsPerSample', 8);

Now I also want to input noise into the process

Does anyone know how the code should be used?

thank you

Answer 1

[Mathieu NOE]

hello

if you simply want to add some white noise you can do this

[y,Fs]=audioread('water.wav');
 y = y + 0.1*randn(size(y)); % adjust amplitude to your needs
 y = y./max(abs(y)); % normalize data to avoid saturation (may be depend on output format)
audiowrite('testing.flac',y,Fs,'BitsPerSample', 8);

you can also add a low or high or bandpass filter on the random noise if you want to have noise in a certain frequency range.

[Sisi Misi]

alright Mr, thank you

But I have another question, when I listen to the results I completely lose the original audio. What if we want to input noise into the audio but the original audio is still heard and can keep the audio in 2 channels, because my original audio is 2 channels?

I'm confused because I'm using lossless compression here

[Mathieu NOE]

hello

could you share your wav file ? the amount (amplitude) of noise must be adapted to the amplitude of your sgnal so you must probably do some trials

if you can share your wav file I can further help you;

[Sisi Misi]

https://drive.google.com/drive/folders/1OkoSw7a-DQ0rFhPDIIUsQ_95BzOaKANS?usp=sharing

This is the audio folder Mr

This audio is obtained from the music cloud

This audio consists of two channels, I did a lossless compression process (into a .flac format codec) with variations in bits per sample (24, 16, and 8 bits) and in the transmission process I had to put noise into it. Then decompress it back into a wav file

I want to see the performance of the lossless audio codec how resistant the audio is to noise, because what I read for lossless compression is noise resistance

I hope you can help me because I'm still confused about what I'm doing now

Thank you very much Mr

[Mathieu NOE]

hello

I simply reduced the noise amplitude so it's now clearly audible in the flac version , without hiding the audio content. You can still adjust the amplitude (here 0.01) to your needs and play with flac resolution

[y,Fs]=audioread('water.wav');

 y = y + 0.01*randn(size(y)); % adjust noise amplitude to your needs
 y = y./max(abs(y)); % normalize data to avoid saturation (may be depend on output format)
audiowrite('testing.flac',y,Fs,'BitsPerSample', 8);

[Sisi Misi]

alright Mr

how to keep the new audio that is saved in two channels?

is there any code to add?

[Mathieu NOE]

the output in flac is stereo , I didn't changed anything to the audio size (2 channels)

[Sisi Misi]

ok Mr

In matlab 2015b there is an error like this :

but after i tried it in matlab online

everything is fine

I'm sorry Mr

Thank you so much

[Mathieu NOE]

my pleasure

[Image Analyst]

There should be no difference between local and online versions of MATLAB. Can you reproduce this error?

[Mathieu NOE]

Maybe my fault

this should avoid any issue now :

replace

 y = y./max(abs(y)); % normalize data to avoid saturation (may be depend on output format)

with

 y = y./max(abs(y),[],'all'); % normalize data to avoid saturation (may be depend on output format)

[Sisi Misi]

I don't know Mr

There is still an error here, when I use

[y,Fs]=audioread('water.wav');
y = y + 0.01*randn(size(y)); % adjust noise amplitude to your needs
y = y./max(abs(y),[],'all');% normalize data to avoid saturation (may be depend on output format)
audiowrite('testing8.flac',y,Fs,'BitsPerSample', 8);
audiowrite('testing8.wav',y,Fs)

so I try another code like this, but still errorr

[y,Fs]=audioread('water.wav');
y = y + 0.01*randn(size(y)); % adjust noise amplitude to your needs
y = y./max(abs(y),[],'omitnan');% normalize data to avoid saturation (may be depend on output format)
audiowrite('testing8.flac',y,Fs,'BitsPerSample', 8);
audiowrite('testing8.wav',y,Fs)

but in matlab online, everything is fine Mr

[Mathieu NOE]

hello

I think the older 2015 release is not compatible with the syntax max(abs(y),[],'all');

I use the R2020b with works fine.

in case you stick to R2015 , try this modification :

% normalize data to avoid saturation (may be depend on output format) 
%  m = max(abs(y),[],'all'); % R2020
 m = max(abs(y(:)));        % R2015 and below   
 y = y./m; % normalize data 

[Sisi Misi]

okay Mr

It works in matlab 2015b

thank you for helping me

[Mathieu NOE]

My pleasure

[Sisi Misi]

Hi Mr Mathieu NOE

I want to ask you again

I got instructions again to input noise into the audio when we transmit

it means when we do compression

in the "audiowrite" function and in that function we directly input the noise

can we do that Mr ?

[Mathieu NOE]

hello

the compression is done inside the audiowrite function , depending of the format (flac is compressed)

you don't have to do anything in your own code as compression is done by audiowrite function

[Sisi Misi]

yes Mr

I mean, we input noise into the compressed audio instead of the original audio

or maybe when we save the compressed audio we input the noise,

the point is that the input noise is not original audio but compressed audio, immediately when we save the compressed audio

do you understand what I mean Mr ?

sorry I'm confused how to convey it, I hope you understand

because really I need your help

thank you Mr

[Mathieu NOE]

hello

so far the code will add the noise to the original audio , not the compressed audio

the compression is done after the noise is added (y = y + 0.01*randn(size(y));) , because as explained above , the compression is done inside audiowrtite when you select a certain type of format (wav and flac are both compressed audio formats)

[Sisi Misi]

Okay Mr, thank you so much