Channel distortion/noise simulation on recorded audio files

Question

I want to simulate channel distortion/noise such as telephony, VOIP and etc. on some previously recorded audio files. Can someone guide me by recommending some tools in this area?

I'm looking for Linux (Debian) programs, preferably free.

Answer 1

You can use Matlab or its open source alternative Octave.

An example of how this can be accomplished in Matlab:

Here is the code that I used:

load handel.mat             % An example dataset included in Matlab
subplot(2,1,1)
plot(y)                     %Plot the graph without noise
title('Without noise'); 
y = y + randn(size(y))*.1;  % Add additive white gaussian noise
subplot(2,1,2);
plot(y)                     %plot the signal with noise
title('With Additive white gaussian noise')
sound(y,Fs)                 % play the sound

You can add different types of noise with different signal to noise ratios. It is also possible to achieve the same in Octave. You are only limited by imagination when you use these powerful tools.