How to add repeated beeps to sound created with a pause in between each beep in MATLAB
Any pause can be done by using vector/matrix concatenation. Let's say you want to make a signal with pause of length P after it, then do the following:

P = 400;
beep = [sound_array; zeros(P, 2)];


Now if you want to make arbitrary number K of your beeps then use the repmat function as follows:

K = 5;
beeps = repmat(beep, K, 1);


Please read more about matrix concatenation here if you wish.

I believe that with your current code, because you use sound function, signals will be played at the same time. I suggest you to use the pause function to separate playbacks, i.e.:

sound(...)
pause(1)
sound(...)


To create a 1 second pause between playback starts.