% Ring Modulate with a sine wave frequency Fc
Fc = 440;
carrier= sin(2*pi*index*(Fc/Fs))'; 

%create a modulator sine wave frequency Fx
Fx = 200;
modulator = sin(2*pi*index*(Fx/Fs))'; 

% Ring Modulate with sine wave, freq. Fc
y = modulator.*carrier;

% write output
audiowrite('twosine_ringmod.wav', y,Fs);