Creating 2D array to play audio in left and right channel in matlab I'm new to matlab sound processing and I am trying to create a 2D array for the sound code below. I have to make the sound have 400 samples(i.e 10ms) at 20hz, but having trouble getting the code to work. Any help would be greatly appreciated. 
The steps are:
(1)    Construct a two-dimensional array (n x 2  array, i.e., 2 columns, n rows, n is the number of samples per sound channel).  The array is the sound signal, the first column is the sound for the left channel (left speaker), the second column is the sound for the right channel (right speaker)
(2)    Then play the sound.

Fs = 44100;
t = [0:4/Fs:4-4/Fs];
freq = 20;
f1 = sin(2*pi*freq*t);
f2 = sin(2*pi*2*freq*t);
%Sound 1
sound(f1,Fs);
%Sound 2
sound(f2,Fs);
%Play Consecutive
f12 = [f1 f2];
sound(f12,Fs);
%Play together
f_12 = [f1+f2];
sound(f_12,Fs);
Since 20 Hz was a little hard to hear with my speakers, I've changed the main frequency to 600 Hz. I guess it should work:

clc;
clear all;

Fs = 44100; 
N = 40000; % sample size
t = (1:N)*(1/Fs); 
freq = 600; 

sound_array = zeros(N, 2); % initializes a N x 2 matrix
sound_array(:,1) = sin(2*pi*freq*t); 
sound_array(:,2) = sin(2*pi*2*freq*t); 

% Sound 1 
sound(sound_array(:,1),Fs); 

% Sound 2 
sound(sound_array(:,2),Fs); 

% Play the first column at left channel and the second column at the right
% channel
sound(sound_array,Fs);


In fact, if you use the entire array as input in sound, the first column will go to the left channel and the second column to the right channel.