Simulating spatial perception - with cosine wave based sound - in MATLAB I'm trying to create cosine wave, one for the right channel and another for the left. The one on the left is to be moved in phase to simulate change to the spatial perception of the tone. A delay in time to the left side makes us think the sound comes from the right, and since time is converted to phase in a cosine I am working with the phase. 
I wish to use a $500\textrm{ Hz}$ cosine and a $2\textrm{ mSec}$ signal. MT ultimate goal here is to have 9 sounds to simulate the locations around a person's head.  1-4 being left, 5 the center and 6-9 the right. 
This a snippet of the code responsible for this:

t = [ 0 : 1 : 2000 ];   % Time Samples
f = 500;    % Input Signal Frequency 500Hz
fs = 44100; % Sampling Frequency

x =  cos(2 * pi * f / fs * t);  % Generate Sine Wave  

y =  cos(2 * pi * f / fs * t - DELAY);  % Generate Sine Wave  

Y = [x,y];

audiowrite(['file' num2str(j) '.wav'], Y, fs);


The issue I'm having is that no matter what values I try for DELAY the resulting file sounds just like any other, I cannot hear any change.
What am I doing wrong?
Try this

DELAY = 0.5e-3; % half a millisecond for starters. 
t = [ 0 : 1 : 2000 ]';   % Time Samples, COLUMN vector
f = 500;    % Input Signal Frequency 500Hz
fs = 44100; % Sampling Frequency
x =  cos(2 * pi * f / fs * t);  % Generate Sine Wave
y =  cos(2 * pi * f * ( t/fs - DELAY));  % Generate Sine Wave
Y = [x,y];


A bunch of problems with your code


Your variable t was a row vector so you generated a mono output signal
The units of your DELAY variable are unclear. I have written it in a way so that it is in actual seconds.