How could add noise to a music file in a way that after a certain amount of time the music file become noise free?

multiplier = 0.1;
noise = randn(length(y),1).*multiplier; 
sound_w_noise = y+noise;

sound(sound_w_noise,Fs); 

As of now, the noise lasts the entire music file. So far I have tried creating different arrays with different lengths then using that to create the noise, like here.

ys = y(1:57344);
multiplier = 0.1;
noise = randn(length(ys),1).*multiplier; 
sound_w_noise = ys+noise;

sound(sound_w_noise,Fs); 

But all that has done is cut short the music file itself. What could I do so that the noise only lasts for a certain amount of time of the total music file?

Answer 1

[Thiago Henrique Gomes Lobato]

You were almost there. The array you have to shorten is the noise one, while, at the same time, adding it only at the initial values of your sound:

LenNoise = 57344;
multiplier = 0.1;
noise = randn(LenNoise,1).*multiplier; 
sound_w_noise = y;
sound_w_noise(1:LenNoise) = sound_w_noise(1:LenNoise)+noise;
sound(sound_w_noise,Fs); 

[Image Analyst]

Looks a lot like Kylie's question.