Creating 2D array to play audio in left and right channel in matlab
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.