Matlab - Iterating through an array and appending to a new one?

Question

I got an array that is a audio recording, and I'd like to add some noise on it so later I can remove it in Simulink and compare the original to the one that I removed the noise. My problem is that I'm pretty new to Matlab's languages/functions, so I got stucked in a for loop that I didnt understand how It works properly in Matlab. I got this huge array (voice recorded): voice = [0.0012 0.0012; 0.0003 0.0005; (....) (....);] And what I'd like to do is to add some values to each line, so it will be noisy (another array): noise = [0.0142 0.0143] To do It I would do line by line in python with a pseudo code like this: new_audio = [] for line in voice: new_line = (line+noise) new_audio.append(new_line) I need to keep the original so I can compare later. Could you guys give me a hand on it? I'd love to know how to make it happen in Matlab. Obs: (This is also me trying to update an oldcode from my teacher so It works in new Matlab for other students)

Answer 1

MATLAB likes you to set initialize all the variables in the beginning, so make a new matrix called new_audio and save that to be a zero matrix with the same size as original audio recording. A matrix is specifically a 2-D array in MATLAB speak.

You could either:

(1) use a for loop to step through each of the rows of both the new_audio and voice matrixes, add the noise to each row of the new_audio matrix, and save the result to the new_audio matrix.

(2) use the 'repmat' function to duplicate the noise such that there is a new matrix with m rows, where m is the number of rows in the voice matrix. Add this noise matrix to the voice matrix to get your new_audio matrix. This is probably the easiest for MATLAB to do, as more for loops takes more computation time.