You do not hear it because as a single Gaussian pulse, it is far below the range of human hearing, and probably below the ability of soundcards to reproduce it. If you modulate it by a sound that you are able to hear, you can hear it, as the envelope of the sound.
Try this:
mu = 0;
sigma = 5;
x = -16*sigma:1e-3:16*sigma;
y1 = pdf('normal', x, mu, sigma);
y2 = sin(2*pi*x*100) .* y1 * 1E+6;
plot(x, y1)
soundsc(y2,8000);
Here, ‘y2’ creates the ‘carrier’ and modulates it by ‘y1’. You can hear the Gaussian pulse fade in and fade out if you increase ‘sigma’ to 5 or more, and use soundsc instead of sound.
